## June 15, 2018

### Continuum Analytics

#### Introducing Dask for Scalable Machine Learning

Although Python contains several powerful libraries for machine learning, unfortunately, they don’t always scale well to large datasets. This has forced data scientists to use tools outside of the Python ecosystem (e.g., Spark) when they need to process data that can’t fit on a single machine. But thanks to Dask, data scientists can now use …

The post Introducing Dask for Scalable Machine Learning appeared first on Anaconda.

## June 14, 2018

### Matthew Rocklin

This work is supported by Anaconda Inc.

I’m pleased to announce the release of Dask version 0.18.0. This is a major release with breaking changes and new features. The last release was 0.17.5 on May 4th. This blogpost outlines notable changes since the last release blogpost for 0.17.2 on March 21st.

conda install dask


or pip install from PyPI:

pip install dask[complete] --upgrade


Full changelogs are available here:

We list some breaking changes below, followed up by changes that are less important, but still fun.

## Context

The Dask core library is nearing a 1.0 release. Before that happens, we need to do some housecleaning. This release starts that process, replaces some existing interfaces, and builds up some needed infrastructure. Almost all of the changes in this release include clean deprecation warnings, but future releases will remove the old functionality, so now would be a good time to check in.

As happens with any release that starts breaking things, many other smaller breaks get added on as well. I’m personally very happy with this release because many aspects of using Dask now feel a lot cleaner, however heavy users of Dask will likely experience mild friction. Hopefully this post helps explain some of the larger changes.

## Notable Breaking changes

### Centralized configuration

Taking full advantage of Dask sometimes requires user configuration, especially in a distributed setting. This might be to control logging verbosity, specify cluster configuration, provide credentials for security, or any of several other options that arise in production.

We’ve found that different computing cultures like to specify configuration in several different ways:

1. Configuration files
2. Environment variables
3. Directly within Python code

Now we centralize configuration in the dask.config module, which collects configuration from config files, environment variables, and runtime code, and makes it centrally available to all Dask subprojects. A number of Dask subprojects (dask.distributed, dask-kubernetes, and dask-jobqueue), are being co-released at the same time to take advantage of this.

If you were actively using Dask.distributed’s configuration files some things have changed:

1. The configuration is now namespaced and more heavily nested. Here is an example from the dask.distributed default config file today:

distributed:
version: 2
scheduler:
allowed-failures: 3     # number of retries before a task is considered bad
work-stealing: True     # workers should steal tasks from each other
worker-ttl: null        # like '60s'. Workers must heartbeat faster than this

worker:
multiprocessing-method: forkserver
use-file-locking: True

2. The default configuration location has moved from ~/.dask/config.yaml to ~/.config/dask/distributed.yaml, where it will live along side several other files like kubernetes.yaml, jobqueue.yaml, and so on.

However, your old configuration files will still be found and their values will be used appropriately. We don’t make any attempt to migrate your old config values to the new location though. You may want to delete the auto-generated ~/.dask/config.yaml file at some point, if you felt like being particularly clean.

### Replaced the common get= keyword with scheduler=

Dask can execute code with a variety of scheduler backends based on threads, processes, single-threaded execution, or distributed clusters.

Previously, users selected between these backends using the somewhat generically named get= keyword:

x.compute(get=dask.threaded.get)


We’ve replaced this with a newer, and hopefully more clear, scheduler= keyword:

x.compute(scheduler='threads')
x.compute(scheduler='processes')


The get= keyword has been deprecated and will raise a warning. It will be removed entirely on the next major release.

Related to the configuration changes, we now include runtime state in the configuration. Previously people used to set runtime state with the dask.set_options context manager. Now we recommend using dask.config.set:

with dask.set_options(scheduler='threads'):  # Before
...

...


The dask.set_options function is now an alias to dask.config.set.

This was unadvertised and saw very little use. All functionality (and much more) is now available in Dask-ML.

### Other

• We’ve removed the token= keyword from map_blocks and moved the functionality to the name= keyword.
• The dask.distributed.worker_client automatically rejoins the threadpool when you close the context manager.
• The Dask.distributed protocol now interprets msgpack arrays as tuples rather than lists.

## Fun new features

### Arrays

#### Generalized Universal Functions

Dask.array now supports Numpy-style Generalized Universal Functions (gufuncs) transparently. This means that you can apply normal Numpy GUFuncs, like eig in the example below, directly onto a Dask arrays:

import dask.array as da
import numpy as np

# Apply a Numpy GUFunc, eig, directly onto a Dask array
x = da.random.normal(size=(10, 10, 10), chunks=(2, 10, 10))
w, v = np.linalg._umath_linalg.eig(x, output_dtypes=(float, float))
# w and v are dask arrays with eig applied along the latter two axes


Numpy has gufuncs of many of its internal functions, but they haven’t yet decided to switch these out to the public API. Additionally we can define GUFuncs with other projects, like Numba:

import numba

@numba.vectorize([float64(float64, float64)])
def f(x, y):
return x + y

z = f(x, y)  # if x and y are dask arrays, then z will be too


What I like about this is that Dask and Numba developers didn’t coordinate at all on this feature, it’s just that they both support the Numpy GUFunc protocol, so you get interactions like this for free.

#### New “auto” value for rechunking

Dask arrays now accept a value, “auto”, wherever a chunk value would previously be accepted. This asks Dask to rechunk those dimensions to achieve a good default chunk size.

x = x.rechunk({
0: x.shape[0], # single chunk in this dimension
# 1: 100e6 / x.dtype.itemsize / x.shape[0],  # before we had to calculate manually
1: 'auto'      # Now we allow this dimension to respond to get ideal chunk size
})

# or
x = da.from_array(img, chunks='auto')


This also checks the array.chunk-size config value for optimal chunk sizes

>>> dask.config.get('array.chunk-size')
'128MiB'


To be clear, this doesn’t support “automatic chunking”, which is a very hard problem in general. Users still need to be aware of their computations and how they want to chunk, this just makes it marginally easier to make good decisions.

#### Algorithmic improvements

Dask.array gained a full einsum implementation thanks to Simon Perkins.

Also, Dask.array’s QR decompositions has become nicer in two ways:

1. They support short-and-fat arrays
2. The tall-and-skinny variant now operates more robustly in less memory. Here is a friendly GIF of execution:

This work is greatly appreciated and was done by Jeremy Chan.

Native support for the Zarr format for chunked n-dimensional arrays landed thanks to Martin Durant and John A Kirkham. Zarr has been especially useful due to its speed, simple spec, support of the full NetCDF style conventions, and amenability to cloud storage.

### Dataframes and Pandas 0.23

As usual, Dask Dataframes had many small improvements. Of note is continued compatibility with the just-released Pandas 0.23, and some new data ingestion formats.

Dask.dataframe is consistent with changes in the recent Pandas 0.23 release thanks to Tom Augspurger.

#### Orc support

Orc is a format for tabular data storage that is common in the Hadoop ecosystem. The new dd.read_orc function parallelizes around similarly new ORC functionality within PyArrow . Thanks to Jim Crist for the work on the Arrow side and Martin Durant for parallelizing it with Dask.

The dd.read_json function matches most of the pandas.read_json API.

This came about shortly after a recent PyCon 2018 talk comparing Spark and Dask dataframe where Irina Truong mentioned that it was missing. Thanks to Martin Durant and Irina Truong for this contribution.

### Joblib

The Joblib library for parallel computing within Scikit-Learn has had a Dask backend for a while now. While it has always been pretty easy to use, it’s now becoming much easier to use well without much expertise. After using this in practice for a while together with the Scikit-Learn developers, we’ve identified and smoothed over a number of usability issues. These changes will only be fully available after the next Scikit-Learn release (hopefully soon) at which point we’ll probably release a new blogpost dedicated to the topic.

This release is timed with the following packages:

2. distributed

There is also a new repository for deploying applications on YARN (a job scheduler common in Hadoop environments) called skein. Early adopters welcome.

## Acknowledgements

Since March 21st, the following people have contributed to the following repositories:

The core Dask repository for parallel algorithms:

• Andrethrill
• Beomi
• Brendan Martin
• Christopher Ren
• Guido Imperiale
• Diane Trout
• fjetter
• Frederick
• Henry Doupe
• James Bourbeau
• Jeremy Chen
• Jim Crist
• John A Kirkham
• Jon Mease
• Jörg Dietrich
• Ksenia Bobrova
• Larsr
• Marc Pfister
• Markus Gonser
• Martin Durant
• Matt Lee
• Matthew Rocklin
• Pierre-Bartet
• Scott Sievert
• Simon Perkins
• Stefan van der Walt
• Stephan Hoyer
• Tom Augspurger
• Uwe L. Korn
• Yu Feng

The dask/distributed repository for distributed computing:

• Bmaisonn
• Grant Jenks
• Henry Doupe
• Irene Rodriguez
• Irina Truong
• John A Kirkham
• Joseph Atkins-Turkish
• Kenneth Koski
• Loïc Estève
• Marius van Niekerk
• Martin Durant
• Matthew Rocklin
• Olivier Grisel
• Russ Bubley
• Tom Augspurger
• Tony Lorenzo

• Brendan Martin
• J Gerard
• Matthew Rocklin
• Olivier Grisel
• Yuvi Panda

• Guillaume Eynard-Bontemps
• jgerardsimcock
• Joe Hamman
• Joseph Hamman
• Loïc Estève
• Matthew Rocklin
• Ray Bell
• Rich Signell
• Shawn Taylor
• Spencer Clark

The dask-ml repository for scalable machine learning:

• Christopher Ren
• Jeremy Chen
• Matthew Rocklin
• Scott Sievert
• Tom Augspurger

### Acknowledgements

Thanks to Scott Sievert and James Bourbeau for their help editing this article.

## June 13, 2018

### Continuum Analytics

#### 2018 Anaconda State of Data Science Report Released

We at Anaconda greatly value our data science community and are always striving to learn more about how you are using our products and how we can improve your overall experience. With this goal in mind, we recently launched our first Anaconda State of Data Science Survey to gain a better understanding of what users …

The post 2018 Anaconda State of Data Science Report Released appeared first on Anaconda.

## June 12, 2018

### Paul Ivanov

#### Get in it

Two weeks ago, Project Jupyter had our only planned team meeting for 2018. There was too much stuff going on for me to write a poem during the event as I had in previous years (2016, and 2017), so I ended up reading one of the pieces I wrote during my evening introvert breaks in Cleveland at PyCon a few weeks earlier.

Once again, Fernando and Matthias had their gadgets ready to record (thank you both!). The video below was taken by Fernando.

# Get in it

Time suspended
Gellatinous reality - the haze
submerged in murky drops summed
in swamp pond of life

believe and strive, expand the mind
A state sublime, when in your prime you came to
me and we were free to flow and fling our
cares, our dreams, our in-betweens, our
rêves perdues, our residue -- the lime of light
the black of sight -- all these converge and
merge the forks of friction filled with fright
and more -- the float of logs that plunges deep
beyond the fray, beyond the keep -- a leap of faith
the lore of rite, with passage clear, let
fear subside, the wealth of confidence will
rise and iron out wrinkles of doubt

Commit to change and stash your pride
then push your luck, and make amends.
Branch out your thoughts, reset assumptions
then checkout.

The force of pulls t'wards master class
Remote of possibilities. Rehash the past
Patch up the present -- what's the diff?

There's nothing left -- except to glide -- and
soar beyond your frame of mind.  try not to pry
cry, freedom, cry.


## June 09, 2018

### Titus Brown

#### How long does it take to produce scientific software?

Over here at UC Davis, the Lab for Data Intensive Biology has been on extended walkabout developing software for, well, doing data intensive biology.

Over the past two to three years or so, various lab members have been working on the following new pieces of software -

I should say that all of these except for kevlar have been explicitly supported by my Moore Foundation funding from the Data Driven Discovery Initiative.

With the possible exception of dammit, every single one of these pieces of software was developed entirely since the move to UC Davis (so, since 2015 or later). And almost all of them are now approaching some reasonable level of maturity, defined as "yeah, not only does this work, but it might be something that other people can use." (Both dammit and sourmash are being used by other people already; kevlar, spacegraphcats, and boink are being written up now.)

All of these coming together at the same time seems like quite a coincidence to me, and I would like to make the following proposition:

It takes a minimum of two to three years for a piece of scientific software to become mature enough to publicize.

This fits with my previous experiences with khmer and the FamilyRelations/Cartwheel set of software as well - each took about two years to get to the point where anyone outside the lab could use them.

I can think of quite a few reasons why some level of aging could be necessary -

• often in science one has no real idea of what you're doing at the beginning of a project, and that just takes time to figure out;

• code just takes time to get reasonably robust when interfacing with real world data;

• there are lots of details that need to be worked out for installation and distribution of code, and that also just takes time;

but I'm somewhat mystified by the 2-3 year arc. It could be tied to the funding timeline (the Moore grant ends in about a year) or career horizons (the grad students want to graduate, the postdocs want to move on).

My best guess, tho, is that there is some complex tradeoff between scope and effort that breaks the overall software development work into multiple stages - something like,

1. figure out the problem
2. implement a partial solution
3. make an actual solution
4. expand solution cautiously to apply to some other nearby problems.

I'm curious as to whether or not this pattern fits with other people's experiences!

I do expect these projects to continue maturing as time and opportunity permits, much like khmer. boink, spacegraphcats, and sourmash should all result in multiple papers from my lab; kevlar will probably move with Daniel to his next job, but may be something we also extend in our lab; etc.

Another very real question in my mind is: which software do we choose to maintain and extend? It's clearly dependent on funding, but also on the existence of interesting problems that the software can still address, and on who I have in my lab... right now a lot of our planning is pretty helter skelter, but it would be good to articulate a list of guiding considerations for when I do see pots of money on the horizon.

Finally: I think this 2-3 year timeline has some interesting implications for the question of whether or not we should require people to release usable software. I think it's a major drain on people to expect them to not only come up with some cool new idea and implement it in software they can use, but then also make software that is more generally usable. Both sides of this take special skills - some people are good at methods & algorithms development, some people are good at software development, but very few people are good at both. And we should value both, but not require that people be good at both.

--titus

## June 02, 2018

### Titus Brown

#### Detecting microbial contamination in long-read assemblies (from known microbes)

A week ago, Erich Schwarz e-mailed our lab list asking,

I would like to be able to download a set of between 1,000 and 10,000 bacterial genome assembly sequences that are reasonably representative of known bacteria. RefSeq's bacterial genome set is easy to download, but absolutely freaking huge (the aggregate FASTA file for its genome sequences is 410 GB).

After digging in a bit, Erich gave us his actual goal: to search for potential microbial contaminants, like so:

Do MegaBlastN on new genome assemblies from PacBio data. With PacBio one gets very few large contigs, so bacterial contamination is really easy to filter out with a simple MegaBlastN. However, I did my last big download of 3,000 microbial genomes from EBI in 2013. There's a lot more of them now!

My response:

I think sourmash gather on each contig would probably do the right thing for you, actually; https://sourmash.readthedocs.io/en/latest/tutorials.html if you have a "true positive" contaminated scaffold to share, I can test that fairly quickly.

Also - I assume the contigs are never chimeric, so if you find contamination in one it's ok to discard the whole thing?

Also - kraken should do a fine job of this albeit in a more memory intensive way. MegaBlastN isn't not much more sensitive than k-mer based approaches, I think.

This would let Erich search all 100k+ bacterial genomes without downloading the complete genomes. My recommendation was to do this to identify candidate genomes for contaminants, and then use something like mashmap to do a more detailed alignment and contaminant removal.

Erich responded with some useful links.

In fact, I have what should be both positive and negative controls for microbial contamination:

http://woldlab.caltech.edu/~schwarz/caeno_pacbio.previous/nigoni_mhap.decont_2015.11.11.fa.gz
http://woldlab.caltech.edu/~schwarz/caeno_pacbio.previous/nigoni_mhap.CONTAM_2015.11.11.fa.gz


which you are very welcome to try sourmashing!

After some other back and forth, I wrote a script to do the work; here's a rough run protocol:

curl -O -L http://woldlab.caltech.edu/~schwarz/caeno_pacbio.previous/nigoni_mhap.decont_2015.11.11.fa.gz
./gather-by-contig.py nigoni_mhap.CONTAM_2015.11.11.fa.gz genbank-k31.sbt.json --output-match foo.txt --output-nomatch foo2.txt —csv summary.csv


which should take a minute or two to run on a modern SSD laptop, and requires less than 1 GB of RAM (and about 18 GB of disk space for the genbank index).

A few comments before I go through the script in detail:

• this uses MinHash downsampling as implemented in sourmash, so you have to feed long contigs in. This is appropriate for PacBio and Nanopore assemblies, but not for raw reads of any kind, and probably not for Illumina assemblies.
• sourmash will happily do contaminant estimation of an entire data set (genomes, reads, etc.) - the goal here was to go line by line through the contigs and split them into "match" and "no match".

Last, but not least: this kind of ad hoc scripting functionality is what we aspire to enable with all our software. A command line program can't address all needs, but a default set of functionality provided via the command line, wrapping a more general purpose library, can!

## An annotate version of the script

First, import the necessary things:

#! /usr/bin/env python
import argparse
import screed
import sourmash
from sourmash import sourmash_args, search
from sourmash.sbtmh import SearchMinHashesFindBestIgnoreMaxHash
import csv


In the main function, set up some arguments:

def main():
p = argparse.ArgumentParser()
args = p.parse_args()


Then, find the SBT database to load:

    tree = sourmash.load_sbt_index(args.sbt_database)
print(f'found SBT database {args.sbt_database}')


Next, figure out the MinHash parameters used to construct this database, so we can use them to construct MinHashes for each sequence in the input file:

    leaf = next(iter(tree.leaves()))
mh = leaf.data.minhash.copy_and_clear()

print(f'using ksize={mh.ksize}, scaled={mh.scaled}')


Give some basic info:

    print(f'loading sequences from {args.input_seqs}')
if args.output_match:
print(f'saving match sequences to {args.output_match.name}')
if args.output_nomatch:
print(f'saving nomatch sequences to {args.output_nomatch.name}')
if args.csv:
print(f'outputting CSV summary to {args.csv.name}')


In the main loop, we'll need to track found items (for CSV summary output), and other basic stats:

    found_list = []
total = 0
matches = 0


Now, for each sequence in the input file of contigs:

    for record in screed.open(args.input_seqs):
total += 1
found = False


Set up a search function that finds the best match, and construct a new MinHash for each query sequence:

        search_fn = SearchMinHashesFindBestIgnoreMaxHash().search

query_mh = mh.copy_and_clear()
query = sourmash.SourmashSignature(query_mh)


If the sequence is too small, quit.

        # too small a sequence/not enough hashes? notify
if not query_mh.get_mins():
print(f'note: skipping {query.name[:20]}, no hashes in sketch')
continue


Now do the search, and pull off the first match:

        for leaf in tree.find(search_fn, query, args.threshold):
found = True
matches += 1
similarity = query.similarity(leaf.data)
found_list.append((record.name, leaf.data.name(), similarity))
break


Nothing found? That's ok, just indicate empty.

        if not found:
found_list.append((record.name, '', 0.0))


Output sequences appropriately:

        if found and args.output_match:
args.output_match.write(f'>{record.name}\n{record.sequence}')
args.output_match.write(f'>{record.name}\n{record.sequence}')


and update the user:

        print(f'searched {total}, found {matches}', end='\r')


At the end, print out the summary (this merely leaves the preceding line alone), and output CSVs:

    print('')

if args.csv:
w = csv.DictWriter(args.csv, fieldnames=['query', 'match', 'score'])
for (query, match, score) in found_list:
w.writerow(dict(query=query, match=match, score=score))


Finally, ...call the main function if this is run as a script:

if __name__ == '__main__':
main()


Comments and questions welcome, as always!

best, --titus

## May 31, 2018

### Continuum Analytics

#### Anaconda Distribution 5.2 Released

We’re excited to announce the release of Anaconda Distribution 5.2! With over 6 million users, Anaconda Distribution is the world’s most popular and easiest way to do Python data science and machine learning. Download and install Anaconda Distribution 5.2 now, or update your current Anaconda Distribution installation to version 5.2 by using conda update conda …

The post Anaconda Distribution 5.2 Released appeared first on Anaconda.

## May 30, 2018

### Titus Brown

I've often been disparaging of the community efforts of big academic collaborations, because it seems like they rarely communicate with the outside world well - this is particularly true of interim (not-yet-publishable) results and software. Over the years I've evolved a theory that big consortia are so busy communicating within that they have no energy for communicating without. This robs the larger scientific community of insight and scientific results in a way that I feel like smaller collaborations do not - you could probably come up with "communication per ", or something, as a metric, and I bet large consortia would show poorer numbers. I particularly admire open source communities here, because the communication is often so good (compared, at least, with consortia, or really academics of any kind) and rather fine grained. Since many open source communities are both distributed and asynchronous, they really seem to excel at information sharing in useful ways. (See Max Ogden's excellent doc about how to run an async team if you're interested in some of the lowdown here.) I am hoping to use my coordination position within the #CommonsPilot to facilitate better communication, and we've even hired some people to do that. So imagine my frustration to be in exactly that "silent" situation with the #CommonsPilot! I can now partly confirm my initial theory, and elaborate upon it, with the benefit of about 6 months of experience. Without further ado, here are: ## The top N reasons why I think big consortia are unusually silent. 1. We're too busy talking to each other by e-mail! By the time I finish reading and responding to e-mails (and, ahem, sending new ones) from the #CommonsPilot each day, I'm out of time and energy. 1. We're too busy talking to each other on teleconferences! Most information is passed via in-person teleconferences, from which very little information actually escapes. This is exacerbated by people's interest in ONLY communicating this way, because it leads to more focused and thoughtful engagement by busy academics. It's high bandwidth, sure, but it's also isolating - only the people who have the time and energy to show up for all the teleconferences are in the know. One takeaway that I got from this excellent blog post, aturon.log: listening and trust, part 1, about the Rust community, is that "all major project decisions must go through the RFC process" - which must involve written communication that clearly recapitulates anything discussed on a phone call. We were already instituting this in the Data Commons before this blog post, but now I have extra reasons to do so :) 1. Consortium wide decisions require multiple rounds of discussion before consensus is reached and can be communicated externally. I really don't want to post things that people disagree with, but it takes a lot of time to figure out what that is (and isn't). 1. Rules for communicating with the outside world aren't clear. Funding bodies and senior PIs are often risk averse, and figuring out what is and isn't a risk is tough. We've finally gotten some blogging and Twitter guidelines approved and we'll post them when we can. 1. Hierarchies interfere. Typically the people most familiar with social media are junior in collaborations, and (for better or for worse) are worried about irritating those senior to them by speaking out of turn. Here I have an edge, since I'm both a PI and a coordinator on this project, and my proposal focused on outreach (and this proposal was accepted by the NIH). So I have a mandate. 1. Communicating externally takes time, energy, and willpower. Usually, there's no one whose job it is to communicate with the community. To which I say... ...welcome, Dr. Rayna Harris :). ## Wait, why should we be communicating anyway? I started with the implicit assumption that consortia should be communicating with the outside world. Why?? I think there are many reasons. It's not just about communicating science more effectively, although that's part of it; it's also about: • communicating about what big, expensive consortia are doing that's worthwhile; think "accountability to taxpayers and stakeholders". • gaining buy-in for consortium decisions from the wider community. This is particularly important for efforts like the #CommonsPilot, where we are hoping to identify and implement good standards and build a community of practice. • getting feedback (negative and positive) on consortium decisions. If we're picking tech that is out of date or old or bad, we should know - and we don't always! Perhaps the best reason, though, is that external communication can help people internal to the Consortium understand what's going on. I've often found that there are relatively few people truly "in the loop" in any given situation, and a commitment to external communication of internal decisions can actually help communicate those same internal decisions internally. Or, to put it another way, if you're not communicating in one venue, you're probably not communicating well in any venue, and this is probably harming your consortium and limiting the contributions of people - especially junior people. ## So, what's the status, anyway? More soon, I hope :) --titus p.s. Thanks to VM Brasseur for her comments and suggestions on this post! ## May 28, 2018 ### Titus Brown #### Open-source style community engagement for the Data Commons Pilot Phase Consortium Note: this is a guest post by Dr. Rayna M. Harris. In November 2017, the National Institutes of Health (NIH) announced the formation of a Data Commons Pilot Phase Consortium (DCPPC) to accelerate biomedical discovery by making big biomedical data more findable and usable. It's called a consortium because the awardees are all working together in concert and collaboration to achieve the larger goal. Those awardees (big cats who run academic research labs or companies) have each brought on numerous students, postdocs, and staff, so the size of the consortium has already grown to over 300 people! That's a lot of cats to herd. So, how are we keeping everyone in the community coordinated and engaged? Here's a little insight into our approach, which was first outlined by Titus in this blog post. ## DCPPC Key Capabilities and teams The overall structure of the DCPPC is a little complex, especially to the uninitiated. Members of the consortium organized themselves into "Key Capabilities" or focus groups that correspond to elements of the funding call and the major objectives of the Data Commons. Key Capabilities (KC) 1-9 are described in more detail here. On top of the KC lingo, each of the awardees all adopted team names from the elements of the periodic table, so you'll hear thing things like "KC1 has a meeting on Wednesday" or "Team Copper is meeting on Tuesday". I made infographic below to help myself see the connections between the DCPPC objections, key capacities and teams. I am a member of Team Copper, which consists of members or affiliates of the Data Intensive Biology Lab at UC Davis (C. Titus Brown, Phillip Brooks, Rebecca Calisi Rodriguez, Amanda Charbonneau, Rayna Harris, Luiz Irber, Tamer Mansour, Charles Reid, Daniel Standage and Karen Word), the Biomedical data analysis company Curoverse (Alexander (Sasha) Wait Zaranek, VM (Vicky) Brasseur, Sarah Edrie, Meredith Gamble and Sarah Wait Zaranek), and the Harvard Chan Bioinformatics Core (Brad Chapman, Radhika Khetani and Mary Piper). ## GitHub for project management of 522 milestones and 50 deliverables Very early on, it was decided that GitHub would be our authoritative and canonical source for all DCPPC milestones and deliverables. What are milestones and deliverables? Milestones are team-defined tasks that must be completed in order to achieve the long-term objective of the DCPPC. Deliverables are the currency by which we evaluate whether or not a milestone has been reached. Deliverables can be in either the form of a demo (activities or documentation that demonstrate completion of goals of the Commons) or products (resources such as standards and conventions, APIs, data resources, websites, repositories, documentation, and training or outreach materials). The DCPPC has defined 522 milestones and 50 deliverables that are due in the first 180 days (between April 1 and September 28, 2018). _Why GitHub?__ We chose GitHub because it makes cross-project linking and commenting easy and many people are familiar with it. How did we get all the information about 500 milestones into GitHub issues? We automated it! One of the first accomplishments of Team Copper was developed a collection of scripts (collectively referred to as the "DCPPC bot") that takes a CSV file of all the milestones and deliverables and opens GitHub issues with a brief description, a due date, and a label corresponding to the relevant Team. We also interlink the milestones corresponding to each deliverable. Right now, the DCPPC bot only deals with DCPPC milestones and deliverables, but you could imagine how this tools could be modified and adapted to many other large-scale community projects. ## On-boarding existing and new members To get everyone on the same page, we put in place some loose guidelines for communication (we'll be using this platform for e-mail, that project for documents, etc.). We defined a community code of conduct and have adopted open and transparent workflows to the best of our ability. We wrote some simple onboarding documents and checklists to connect people to those guidelines, communication channels, and useful resources. New members fill out a Google form providing basic contact information and their affiliation to the DCPPC. Then Team Copper gives them access to all the various communication channels. Finally, we send a follow-up email pointing new members to all the relevant resources and documentation. We haven't perfected on onboarding process, but this thank you note is evidence that we are on the right track! "Thank you so much for this information! I just started with [the DCPPC] 3 weeks ago and the learning curve has been steep. These docs have been the best crash course. Thank you!" - Anonymous DCPPC member It is important to note that we are paying attention to what communication avenues are actually being used or working well and are fine-tuning accordingly. For instance, we started using Google Calendars, but it wasn't working, so we switched to the Groups.io calendar. Our goal is to layer on more structure only when the need becomes apparent (but without doing so too early or often) to preserve flexibility and adaptation to suit the needs of the community. The best thing (in my opinion) about using Groups.io, GitHub, and Slack for communication is that new members have access to all the conversation that has taken place since the beginning. This provides a wealth of information that would be lost if all communication took place via personal email or face to face communication. Another excellent feature of the tools we are using is the availability of APIs for automating processes and reconciling access lists. We configured our groups.io calendars to automatically post upcoming meeting notifications to the appropriate Slack channel, so that's cool! We also built a tool that calls the Slack, GitHub, and Groups.io APIs and returns a list of everyone with access. This is really useful for checking to be sure that everyone who needs access has it (or that no one who shouldn't doesn't). ## Monthly, unconference style meetings and hackathons Virtual tools like Slack, GitHub, Twitter, and Zoom make synchronous and asynchronous communication possible from nearly anywhere in the world, but the power of face to face (f2f) communication is undeniable a powerful way to boost collaboration and creativity. As a testament to the Consortium’s commitment to community engagement, a significant part of our budget is being used to cover all the associated travel, lodging, and food costs. Team Copper (see the list of members below) has taken on the role of organizing or facilitating these f2f meeting. We are adopting an "unconference style" format where the attendees determine the topics of discussion or direction of a hackathon. The goal of the first f2f meetings in December 2017 was to determine what the DCPPC actually needed to do during the first 180 days of this effort (aka Pilot Phase I). This meeting was attended by NIH staff, awardees, cloud service providers, and data stewards. You can read more about the outcomes of this meeting in a blog post written by C. Titus Brown. The second f2f meeting took place on April 2018. The goal of the April meeting the goal was to showcase our progress to the NIH. Moving forward, we are planning a f2f meeting every month at various sites around the US. The goals of the DCPPC May workshop are to build community, to facilitate planned and serendipitous collaboration across teams, and to surface hidden issues around technical and conceptual interoperability. A major focus of the June meeting will be a multi-team, multi-KC hackathon. The goals and topics for our meetings in July - October meetings have yet to be determined but will likely correspond to relevant milestones and deliverable that are due those months or the near future. ## Want more updates? There's a lot that I didn't cover, so stay tuned for more in-depth blog posts about building an open-source style community around the Data Commons. In the mean time, get regular updates by following the #CommonsPilot hashtag or the @nih_dcppc ‏and @NIH_CommonFund accounts on Twitter. ## May 27, 2018 ### Matthew Rocklin #### Beyond Numpy Arrays in Python ## Executive Summary In recent years Python’s array computing ecosystem has grown organically to support GPUs, sparse, and distributed arrays. This is wonderful and a great example of the growth that can occur in decentralized open source development. However to solidify this growth and apply it across the ecosystem we now need to do some central planning to move from a pair-wise model where packages need to know about each other to an ecosystem model where packages can negotiate by developing and adhering to community-standard protocols. With moderate effort we can define a subset of the Numpy API that works well across all of them, allowing the ecosystem to more smoothly transition between hardware. This post describes the opportunities and challenges to accomplish this. We start by discussing two kinds of libraries: 1. Libraries that implement the Numpy API 2. Libraries that consume the Numpy API and build new functionality on top of it ## Libraries that Implement the Numpy API The Numpy array is one of the foundations of the numeric Python ecosystem, and serves as the standard model for similar libraries in other languages. Today it is used to analyze satellite and biomedical imagery, financial models, genomes, oceans and the atmosphere, super-computer simulations, and data from thousands of other domains. However, Numpy was designed several years ago, and its implementation is no longer optimal for some modern hardware, particularly multi-core workstations, many-core GPUs, and distributed clusters. Fortunately other libraries implement the Numpy array API on these other architectures: • CuPy: implements the Numpy API on GPUs with CUDA • Sparse: implements the Numpy API for sparse arrays that are mostly zeros • Dask array: implements the Numpy API in parallel for multi-core workstations or distributed clusters So even when the Numpy implementation is no longer ideal, the Numpy API lives on in successor projects. Note: the Numpy implementation remains ideal most of the time. Dense in-memory arrays are still the common case. This blogpost is about the minority of cases where Numpy is not ideal So today we can write code similar code between all of Numpy, GPU, sparse, and parallel arrays: import numpy as np x = np.random.random(...) # Runs on a single CPU y = x.T.dot(np.log(x) + 1) z = y - y.mean(axis=0) print(z[:5]) import cupy as cp x = cp.random.random(...) # Runs on a GPU y = x.T.dot(cp.log(x) + 1) z = y - y.mean(axis=0) print(z[:5].get()) import dask.array as da x = da.random.random(...) # Runs on many CPUs y = x.T.dot(da.log(x) + 1) z = y - y.mean(axis=0) print(z[:5].compute()) ...  Additionally, each of the deep learning frameworks (TensorFlow, PyTorch, MXNet) has a Numpy-like thing that is similar-ish to Numpy’s API, but definitely not trying to be an exact match. ## Libraries that consume and extend the Numpy API At the same time as the development of Numpy APIs for different hardware, many libraries today build algorithmic functionality on top of the Numpy API: 1. XArray for labeled and indexed collections of arrays 2. Autograd and Tangent: for automatic differentiation 3. TensorLy for higher order array factorizations 4. Dask array which coordinates many Numpy-like arrays into a logical parallel array (dask array both consumes and implements the Numpy API) 5. Opt Einsum for more efficient einstein summation operations These projects and more enhance array computing in Python, building on new features beyond what Numpy itself provides. There are also projects like Pandas, Scikit-Learn, and SciPy, that use Numpy’s in-memory internal representation. We’re going to ignore these libraries for this blogpost and focus on those libraries that only use the high-level Numpy API and not the low-level representation. ## Opportunities and Challenges Given the two groups of projects: 1. New libraries that implement the Numpy API (CuPy, Sparse, Dask array) 2. New libraries that consume and extend the Numpy API (XArray, Autograd/tangent, TensorLy, Einsum) We want to use them together, applying Autograd to CuPy, TensorLy to Sparse, and so on, including all future implementations that might follow. This is challenging. Unfortunately, while all of the array implementations APIs are very similar to Numpy’s API, they use different functions. >>> numpy.sin is cupy.sin False  This creates problems for the consumer libraries, because now they need to switch out which functions they use depending on which array-like objects they’ve been given. def f(x): if isinstance(x, numpy.ndarray): return np.sin(x) elif isinstance(x, cupy.ndarray): return cupy.sin(x) elif ...  Today each array project implements a custom plugin system that they use to switch between some of the array options. Links to these plugin mechanisms are below if you’re interested: For example XArray can use either Numpy arrays or Dask arrays. This has been hugely beneficial to users of that project, which today seamlessly transition from small in-memory datasets on their laptops to 100TB datasets on clusters, all using the same programming model. However when considering adding sparse or GPU arrays to XArray’s plugin system, it quickly became clear that this would be expensive today. Building, maintaining, and extending these plugin mechanisms is costly. The plugin systems in each project are not alike, so any new array implementation has to go to each library and build the same code several times. Similarly, any new algorithmic library must build plugins to every ndarray implementation. Each library has to explicitly import and understand each other library, and has to adapt as those libraries change over time. This coverage is not complete, and so users lack confidence that their applications are portable between hardware. Pair-wise plugin mechanisms make sense for a single project, but are not an efficient choice for the full ecosystem. ## Solutions I see two solutions today: 1. Build a new library that holds dispatch-able versions of all of the relevant Numpy functions and convince everyone to use it instead of Numpy internally 2. Build this dispatch mechanism into Numpy itself Each has challenges. ### Build a new centralized plugin library We can build a new library, here called arrayish, that holds dispatch-able versions of all of the relevant Numpy functions. We then convince everyone to use it instead of Numpy internally. So in each array-like library’s codebase we write code like the following: # inside numpy's codebase import arrayish import numpy @arrayish.sin.register(numpy.ndarray, numpy.sin) @arrayish.cos.register(numpy.ndarray, numpy.cos) @arrayish.dot.register(numpy.ndarray, numpy.ndarray, numpy.dot) ...  # inside cupy's codebase import arrayish import cupy @arrayish.sin.register(cupy.ndarray, cupy.sin) @arrayish.cos.register(cupy.ndarray, cupy.cos) @arrayish.dot.register(cupy.ndarray, cupy.ndarray, cupy.dot) ...  and so on for Dask, Sparse, and any other Numpy-like libraries. In all of the algorithm libraries (like XArray, autograd, TensorLy, …) we use arrayish instead of Numpy # inside XArray's codebase # import numpy import arrayish as numpy  This is the same plugin solution as before, but now we build a community standard plugin system that hopefully all of the projects can agree to use. This reduces the big n by m cost of maintaining several plugin systems, to a more manageable n plus m cost of using a single plugin system in each library. This centralized project would also benefit, perhaps, from being better maintained than any individual project is likely to do on its own. However this has costs: 1. Getting many different projects to agree on a new standard is hard 2. Algorithmic projects will need to start using arrayish internally, adding new imports like the following: import arrayish as numpy  And this wll certainly cause some complications interally 3. Someone needs to build an maintain the central infrastructure Hameer Abbasi put together a rudimentary prototype for arrayish here: github.com/hameerabbasi/arrayish. There has been some discussion about this topic, using XArray+Sparse as an example, in pydata/sparse #1 ### Dispatch from within Numpy Alternatively, the central dispatching mechanism could live within Numpy itself. Numpy functions could learn to hand control over to their arguments, allowing the array implementations to take over when possible. This would allow existing Numpy code to work on externally developed array implementations. There is precedent for this. The array_ufunc protocol allows any class that defines the __array_ufunc__ method to take control of any Numpy ufunc like np.sin or np.exp. Numpy reductions like np.sum already look for .sum methods on their arguments and defer to them if possible. Some array projects, like Dask and Sparse, already implement the __array_ufunc__ protocol. There is also an open PR for CuPy. Here is an example showing Numpy functions on Dask arrays cleanly. >>> import numpy as np >>> import dask.array as da >>> x = da.ones(10, chunks=(5,)) # A Dask array >>> np.sum(np.exp(x)) # Apply Numpy function to a Dask array dask.array<sum-aggregate, shape=(), dtype=float64, chunksize=()> # get a Dask array  I recommend that all Numpy-API compatible array projects implement the __array_ufunc__ protocol. This works for many functions, but not all. Other operations like tensordot, concatenate, and stack occur frequently in algorithmic code but are not covered here. This solution avoids the community challenges of the arrayish solution above. Everyone is accustomed to aligning themselves to Numpy’s decisions, and relatively little code would need to be rewritten. The challenge with this approach is that historically Numpy has moved more slowly than the rest of the ecosystem. For example the __array_ufunc__ protocol mentioned above was discussed for several years before it was merged. Fortunately Numpy has recently received funding to help it make changes like this more rapidly. The full time developers hired under this funding have just started though, and it’s not clear how much of a priority this work is for them at first. For what it’s worth I’d prefer to see this Numpy protocol solution take hold. ## Final Thoughts In recent years Python’s array computing ecosystem has grown organically to support GPUs, sparse, and distributed arrays. This is wonderful and a great example of the growth that can occur in decentralized open source development. However to solidify this growth and apply it across the ecosystem we now need to do some central planning to move from a pair-wise model where packages need to know about each other to an ecosystem model where packages can negotiate by developing and adhering to community-standard protocols. The community has done this transition before (Numeric + Numarray -> Numpy, the Scikit-Learn fit/predict API, etc..) usually with surprisingly positive results. The open questions I have today are the following: 1. How quickly can Numpy adapt to this demand for protocols while still remaining stable for its existing role as foundation of the ecosystem 2. What algorithmic domains can be written in a cross-hardware way that depends only on the high-level Numpy API, and doesn’t require specialization at the data structure level. Clearly some domains exist (XArray, automatic differentiation), but how common are these? 3. Once a standard protocol is in place, what other array-like implementations might arise? In-memory compression? Probabilistic? Symbolic? ## Update After discussing this topic at the May NumPy Developer Sprint at BIDS a few of us have drafted a Numpy Enhancement Proposal (NEP) available here. ## May 23, 2018 ### numfocus #### Google Joins NumFOCUS as Corporate Sponsor ## May 18, 2018 ### numfocus #### NumFOCUS Awards Development Grants to Open Source Projects – Spring 2018 ## May 16, 2018 ### Continuum Analytics #### Generate Custom Parcels for Cloudera CDH with Anaconda Enterprise 5 As part of our partnership with Cloudera, we offer a freely available Anaconda Python parcel for Cloudera CDH based on the Anaconda Distribution. The Anaconda parcel has been very well-received by both Anaconda and Cloudera users by making it easier for data scientists and analysts to use libraries from Anaconda that they know and love … Read more → The post Generate Custom Parcels for Cloudera CDH with Anaconda Enterprise 5 appeared first on Anaconda. ### numfocus #### Project Jupyter Receives ACM Software System Award ### Continuum Analytics #### CyberPandas: Extending Pandas with Richer Types By Tom Augspurger, Data Scientist at Anaconda Over the past couple months, Anaconda has supported a major internal refactoring of pandas. The outcome is a new extension array interface that will enable an ecosystem of rich array types, that meet the needs of pandas’ diverse user base. Using the new interface, we’ve built a library … Read more → The post CyberPandas: Extending Pandas with Richer Types appeared first on Anaconda. ## May 10, 2018 ### Travis Oliphant #### Reflections on Anaconda as I start a new chapter with Quansight Leaving the company you founded is always a tough decision and a tough process that involves many people. It requires a series of potentially emotional "crucial-conversations." It is actually not that uncommon in venture-backed companies for one or more of the original founders to leave at some point. There is a decent article on the topic here: https://hbswk.hbs.edu/item/the-founding-ceos-dilemma-stay-or-go. Still it is extremely difficult to let go. You live and breathe the company you start. Years of working to connect as many people as possible to the dream gives you a feeling of "ownership" and connection that no stock certificate can replace. Starting a company is a lot of work. It takes a lot of effort. There are many decisions to make and many voices to incorporate. Hiring, firing, raising money, engaging customers, engaging employees, planning projects, organizing events, and aligning a pastiche of personalities while staying relevant in a rapidly evolving technology jungle is difficult. As a founder over 40 with modest means, I had a family of 6 children who relied on me. That family had teenage children who needed my attention and pre-school and elementary-school children that I could not simply leave only in the hands of my wife. I look back and sometimes wonder how we pulled it off. The truth probably lies in the time we borrowed: time from exercise, time from sleep, time from vacations, and time from family. I'd like to say that this dissonance against "work-life-harmony" was always a bad choice, but honestly, I don't see how I could have made too may different choices and still have created Anaconda. Several things drove me. I could not let the people associated with the company down. I would not lose the money for those that invested in us. I could not let down the people who worked their tail off to build manage, document, market, and sell the technology and products that we produced. Furthermore, I would not let the community of customers and users down that had enabled us to continue to thrive. The only way you succeed as a founder is through your customers being served by the efforts of those who surround you. It is only the efforts of the talented people who joined us in our journey that has allowed Anaconda to succeed so far. It is critical to stay focused on what is in the best interests of those people. Permit me to use the name Continuum to describe the angel-funded and bootstrapped early-stage company that Peter and I founded in 2012 and Anaconda to describe the venture-backed company that Continuum became (This company we called Continuum 2.0 internally that really got started in the summer of 2015 after we raised the first tranche of 22 million from VCs.) Back in 2012, Peter and I knew a few things: 1) we had to connect Python to the Big Data movement; 2) we needed to help the scientific programmer, or a data-scientist developer build visualization-based applications quickly in the web; and 3) we needed to scale the stack of code around the PyData community to bigger hardware and multiple machines. We had big visions of an interconnected data-web, distributed schedulers, and data-structures that traversed the internet which could be analyzed across the cloud with simple Python scripts. We talked and talked about these things and grew misty-eyed in our enthusiasm for the potential of what was possible if we just built the right technology and sold just the right product to fund it. We knew that we wanted to build a product-company -- though we didn't know exactly what those products would be at the outset. We had some ideas, only portions of which actually worked out. I knew how to run a consulting and training company around Python and open-source. Because of this, I felt comfortable raising money from family members. While consulting companies are not "high-growth" they can make real returns for investors. I was pretty confident that I would not lose their money. We raised 2.25million from a few dozen investors consisting of Peter's family, my family, and a host of third-parties from our mutual networks. Peter's family was critical to this early stage because they basically "led the early round" and ensured that we could get off the ground. After they put their money in the bank, we could finish raising the rest of the seed round which took about 6 months to finish. It is interesting (and somewhat embarrassing and so not detailed here) to go back and look at what products we thought we would be making. Some of the technologies we ended up building (like Excel integration, Numba, Bokeh, and Dask) were reflected in those early product dreams. However, the real products and commercial success that Anaconda has had so far are only a vague resemblance to what we thought we would do. Building a Python distribution was the last thing on our minds. I had been building Python distributions since I released SciPy in 2001. As I have often repeated, SciPy was actually the first Python distribution masquerading as a library. The single biggest effort in releasing SciPy was building the binary installers and making sure everything compiled well. With Fortran compilers still more scarce than they should be, it can still be difficult to compile and build SciPy. Fortunately, with conda, conda-forge, and Anaconda, along with the emergence of wheels, almost nobody needs to build SciPy anymore. It is so easy today to get started with a data-science project and get all the software you need to do amazing work fast. You still have to work to maintain your dependencies and keep that workflow reproducible. But, I'm so happy that Anaconda makes that relatively straightforward today. This was only possible because General Catalyst and BuildGroup joined us in the journey in the spring of 2015 to really grow the Anaconda story. Their investment allowed us to 1) convert to a serious product-company from a bootstrapped consulting company with a few small products and 2) continue to invest heavily in conda, conda-forge, and Anaconda. There is nothing like real-world experience as a teacher, and the challenge of converting to a serious product company was a tremendous experience that taught me a great deal. I'm grateful to all the people who brought their best to the company and taught me everyday. It was a privilege and an honor to be a part of their success. I am grateful for their patience with me as my "learning experiences" often led to real struggles for them. There are many lasting learnings that I look forward to applying in future endeavors. The one that deserves mention in this post, however, is that building enterprise software that helps open-source communities should be done by selling a complementary product to the open-source. The "open-core" model does not work as well. I'm a firm believer that there will always be software to sell, but infrastructure should be and will be open-source --- sustained vibrantly from the companies that depend on it. Joel Spolsky has written about complementary products before. You should read his exposition. Early on at Anaconda, Peter and I decided to be a board-led company. This board which includes Peter and I has the final say in company leadership and made the important decision to transition Anaconda from being founder-led to being led by a more experienced CEO. After this transition and through multiple conversations over many months we all concluded that the best course of action that would maximize my energy and passion while also allowing Anaconda to focus on its next chapter would be for me to spin-out of Anaconda and start a new services and open-source company where I could pursue a broader mission. This new company is Quansight (short for Quantitative Insight). Our place-holder homepage is at http://www.quansight.com and we are @quansightai on Twitter. I'm excited to tell you more about the company in future blog-posts and announcements. A few paragraphs will suffice for now. Our overall mission is to develop people, build technology, and discover products to empower people with knowledge and data to solve the world’s most challenging problems. We are doing that currently by connecting organizations sustainably with open source communities to solve their hardest problems by enabling teams to transparently apply science to their data. One of the things we are doing is to help companies get started with AI and ML by applying the entire PyData stack to the fundamental data organization, data visualization, and model management problem that is required for practical success with ML and AI in business. We also help companies generally improve their data-science practice by leveraging all the power of the Python, PyData, and related ecoystems. We are also hard at work on the sustainability problem by continuing the tradition we started at Continuum Analytics of building successful and sustainable open-source "practices" that synchronize company needs with open-source technology development. We have some innovative business approaches to this that we will be announcing in the coming weeks and months. I'm excited that we have several devs working hard to help bring JupyterLab to 1.0 this year along with a vibrant community. There are many exciting extensions to this remarkable platform that remain to be written. We also expect to continue to contribute to the PyViz activities that continue to explode in the Python ecosystem as visualization is a critical first step to understanding and using any data you care about. Finally, Stefan Krah has joined us at Quansight. Stefan is an award-winning Python core developer who has been steadily working over the past 18 months on a small but powerful collection of projects collectively called Plures. These will be more broadly available in the next few months and published under the xnd brand. Xnd is a generic container concept in C with a Python binding that together with its siblings ndtypes and gumath allows building flexible array-computing pipelines over many kinds of data-types. This technology will serve to underly any array-computing framework and be a glue between machine-learning and data-science frameworks of all kinds. Our plan is to use this tool to help reduce the data and computational silos that currently exist across the open-source ecosystem. There is still much to work on and many more technologies to emerge. It's an exciting time to work in machine learning, data-science, and scientific computing. I'm thrilled that I continue to get the opportunity to be part of it. Let me know if you'd like to be a part of our journey. ## May 08, 2018 ### Matthieu Brucher #### Address Sanitizer: alternative to valgrind Recently, at work, I encountered a strange bug with GCC 7.2 and clang 6 (I didn’t test it with Visual Studio 2017 for different reasons). The bug was not visible on “old” compilers like gcc 4, Visual Studio 2013 or even Intel Compiler 2017. In debug mode, everything was fine, but in release mode, the application crashed. But not always at the same location. #### Tools to debug As we run valgrind all the time, I knew that the error could not be found with valgrind. When debugging the error, there was nothing that was wrong. All the variables were defined properly, were local or passed by value (for shared pointers), so nothing popped up. But I had a feeling I would be able to find it with Address Sanitizer. So I ran it with the option ASAN_OPTIONS=detect_stack_use_after_return=1. And then I found it. Use after stack, and where ASAN found the error, I could figure out that we kept a reference to a stack variable that was removed. #### What Address Sanitizer found and how to understand the reports The following piece of code is a simplification of what was written. It may well be that the code was correct the first time it was written because Foo was supposed to be used locally. But in this context, it is not correct. #include <iostream> struct Foo { Foo(const int& bar) : bar(bar) {} const int& bar; }; Foo generate() { int i = 99; return Foo(i); } int main() { Foo foo = generate(); std::cout << foo.bar << std::endl; } As you can see, Foo keeps a reference to an int, and in this case, that integer was allocated on the stack and was destroyed when we access the reference. In debug mode, you would get 99. In optimized mode, you get anything. Literally. To compile it, just do clang++ test.cpp -fsanitizer=address OK, so what does ASAN returns?  ================================================================= ==24406==ERROR: AddressSanitizer: stack-use-after-return on address 0x7f2db2c00040 at pc 0x0000005172e0 bp 0x7ffe043cf770 sp 0x7ffe043cf768 READ of size 4 at 0x7f2db2c00040 thread T0 #0 0x5172df in main (/home/mbrucher/local/temp/a.out+0x5172df) #1 0x7f2db60ffc04 in __libc_start_main (/lib64/libc.so.6+0x21c04) #2 0x41a757 in _start (/home/mbrucher/local/temp/a.out+0x41a757) Address 0x7f2db2c00040 is located in stack of thread T0 at offset 64 in frame #0 0x516fcf in generate() (/home/mbrucher/local/temp/a.out+0x516fcf) This frame has 2 object(s): [32, 40) 'retval' [64, 68) 'i' == Memory access at offset 64 is inside this variable HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext (longjmp and C++ exceptions *are* supported) SUMMARY: AddressSanitizer: stack-use-after-return (/home/mbrucher/local/temp/a.out+0x5172df) in main Shadow bytes around the buggy address: 0x0fe636577fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636577fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636577fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636577fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636577ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0x0fe636578000: f5 f5 f5 f5 f5 f5 f5 f5[f5]f5 f5 f5 f5 f5 f5 f5 0x0fe636578010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636578020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636578030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636578040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe636578050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==24406==ABORTING  The report can be confusing. The trick is to compile with -g to have proper stack information. Here, I get where the bad memory access occurs AND where I stored the wrong reference. Then, the color system allows to check what happens in the memory. Here, it’s only f5, so stack after return information (you could get bound check, deallocated memory…). So we can look for a stack variable that was used, hence the reference that is the culprit. #### Conclusion Address Sanitizer is great. Of course, by default, it checks memory leaks, bound checks… But it can do far more than just these. It is better than valgrind on several aspects, like speed (as it’s not emulation based) but also on what it can check. It saved me lots of time already despite having used it only for a few months, so consider adopting it. It’s a puppy that doesn’t require much time. ## May 03, 2018 ### Thomas Wiecki #### An intuitive, visual guide to copulas (c) 2018 by Thomas Wiecki People seemed to enjoy my intuitive and visual explanation of Markov chain Monte Carlo so I thought it would be fun to do another one, this time focused on copulas. If you ask a statistician what a copula is they might say "a copula is a multivariate distribution C(U_1, U_2, ...., U_n) such that marginalizing gives U_i \sim \operatorname{\sf Uniform}(0, 1)". OK... wait, what? I personally really dislike these math-only explanations that make many concepts appear way more difficult to understand than they actually are and copulas are a great example of that. The name alone always seemed pretty daunting to me. However, they are actually quite simple so we're going to try and demistify them a bit. At the end, we will see what role copulas played in the 2007-2008 Financial Crisis. ## Example problem case¶ Let's start with an example problem case. Say we measure two variables that are non-normally distributed and correlated. For example, we look at various rivers and for every river we look at the maximum level of that river over a certain time-period. In addition, we also count how many months each river caused flooding. For the probability distribution of the maximum level of the river we can look to Extreme Value Theory which tells us that maximums are Gumbel distributed. How many times flooding occured will be modeled according to a Beta distribution which just tells us the probability of flooding to occur as a function of how many times flooding vs non-flooding occured. It's pretty reasonable to assume that the maximum level and number of floodings is going to be correlated. However, here we run into a problem: how should we model that probability distribution? Above we only specified the distributions for the individual variables, irrespective of the other one (i.e. the marginals). In reality we are dealing with a joint distribution of both of these together. Copulas to the rescue. ## What are copulas in English?¶ Copulas allow us to decompose a joint probability distribution into their marginals (which by definition have no correlation) and a function which couples (hence the name) them together and thus allows us to specify the correlation seperately. The copula is that coupling function. Before we dive into them, we must first learn how we can transform arbitrary random variables to uniform and back. All we will need is the excellent scipy.stats module and seaborn for plotting. In [1]: %matplotlib inline import seaborn as sns from scipy import stats  ## Transforming random variables¶ Let's start by sampling uniformly distributed values between 0 and 1: In [2]: x = stats.uniform(0, 1).rvs(10000) sns.distplot(x, kde=False, norm_hist=True);  Next, we want to transform these samples so that instead of uniform they are now normally distributed. The transform that does this is the inverse of the cumulative density function (CDF) of the normal distribution (which we can get in scipy.stats with ppf): In [3]: norm = stats.distributions.norm() x_trans = norm.ppf(x) sns.distplot(x_trans);  If we plot both of them together we can get an intuition for what the inverse CDF looks like and how it works: In [4]: h = sns.jointplot(x, x_trans, stat_func=None) h.set_axis_labels('original', 'transformed', fontsize=16);  As you can see, the inverse CDF stretches the outer regions of the uniform to yield a normal. We can do this for arbitrary (univariate) probability distributions, like the Beta: In [5]: beta = stats.distributions.beta(a=10, b=3) x_trans = beta.ppf(x) h = sns.jointplot(x, x_trans, stat_func=None) h.set_axis_labels('orignal', 'transformed', fontsize=16);  Or a Gumbel: In [6]: gumbel = stats.distributions.gumbel_l() x_trans = gumbel.ppf(x) h = sns.jointplot(x, x_trans, stat_func=None) h.set_axis_labels('original', 'transformed', fontsize=16);  In order to do the opposite transformation from an arbitrary distribution to the uniform(0, 1) we just apply the inverse of the inverse CDF -- the CDF: In [7]: x_trans_trans = gumbel.cdf(x_trans) h = sns.jointplot(x_trans, x_trans_trans, stat_func=None) h.set_axis_labels('original', 'transformed', fontsize=16);  OK, so we know how to transform from any distribution to uniform and back. In math-speak this is called the probability integral transform. ## Adding correlation with Gaussian copulas¶ How does this help us with our problem of creating a custom joint probability distribution? We're actually almost done already. We know how to convert anything uniformly distributed to an arbitrary probability distribution. So that means we need to generate uniformly distributed data with the correlations we want. How do we do that? We simulate from a multivariate Gaussian with the specific correlation structure, transform so that the marginals are uniform, and then transform the uniform marginals to whatever we like. Create samples from a correlated multivariate normal: In [8]: mvnorm = stats.multivariate_normal(mean=[0, 0], cov=[[1., 0.5], [0.5, 1.]]) # Generate random samples from multivariate normal with correlation .5 x = mvnorm.rvs(100000)  In [9]: h = sns.jointplot(x[:, 0], x[:, 1], kind='kde', stat_func=None); h.set_axis_labels('X1', 'X2', fontsize=16);  Now use what we learned above to "uniformify" the marignals: In [10]: norm = stats.norm() x_unif = norm.cdf(x) h = sns.jointplot(x_unif[:, 0], x_unif[:, 1], kind='hex', stat_func=None) h.set_axis_labels('Y1', 'Y2', fontsize=16);  This joint plot above is usually how copulas are visualized. Now we just transform the marginals again to what we want (Gumbel and Beta): In [11]: m1 = stats.gumbel_l() m2 = stats.beta(a=10, b=2) x1_trans = m1.ppf(x_unif[:, 0]) x2_trans = m2.ppf(x_unif[:, 1]) h = sns.jointplot(x1_trans, x2_trans, kind='kde', xlim=(-6, 2), ylim=(.6, 1.0), stat_func=None); h.set_axis_labels('Maximum river level', 'Probablity of flooding', fontsize=16);  Contrast that with the joint distribution without correlations: In [12]: x1 = m1.rvs(10000) x2 = m2.rvs(10000) h = sns.jointplot(x1, x2, kind='kde', xlim=(-6, 2), ylim=(.6, 1.0), stat_func=None); h.set_axis_labels('Maximum river level', 'Probablity of flooding', fontsize=16);  So there we go, by using the uniform distribution as our lingua franca we can easily induce correlations and flexibly construct complex probability distributions. This all directly extends to higher dimensional distributions as well. ## More complex correlation structures and the Financial Crisis¶ Above we used a multivariate normal which gave rise to the Gaussian copula. However, we can use other, more complex copulas as well. For example, we might want to assume the correlation is non-symmetric which is useful in quant finance where correlations become very strong during market crashes and returns are very negative. In fact, Gaussian copulas are said to have played a key role in the 2007-2008 Financial Crisis as tail-correlations were severely underestimated. If you've seen The Big Short, the default rates of individual mortgages (among other things) inside CDOs (see this scene from the movie as a refresher) are correlated -- if one mortgage fails, the likelihood of another failing is increased. In the early 2000s, the banks only knew how to model the marginals of the default rates. This infamous paper by Li then suggested to use copulas to model the correlations between those marginals. Rating agencies relied on this model heavily, severly underestimating risk and giving false ratings. The rest, as they say, is history. Read this paper for an excellent description of Gaussian copulas and the Financial Crisis which argues that different copula choices would not have made a difference but instead the assumed correlation was way too low. ## Getting back to the math¶ Maybe now the statement "a copula is a multivariate distribution C(U_1, U_2, ...., U_n) such that marginalizing gives U_i \sim \operatorname{\sf Uniform}(0, 1)" makes a bit more sense. It really is just a function with that property of uniform marginals. It's really only useful though combined with another transform to get the marginals we want. We can also better understand the mathematical description of the Gaussian copula (taken from Wikipedia): For a given R\in[-1, 1]^{d\times d}, the Gaussian copula with parameter matrix R can be written as C_R^{\text{Gauss}}(u) = \Phi_R\left(\Phi^{-1}(u_1),\dots, \Phi^{-1}(u_d) \right) where \Phi^{-1} is the inverse cumulative distribution function of a standard normal and \Phi_R is the joint cumulative distribution function of a multivariate normal distribution with mean vector zero and covariance matrix equal to the correlation matrix R. Just note that in the code above we went the opposite way to create samples from that distribution. The Gaussian copula as expressed here takes uniform(0, 1) inputs, transforms them to be Gaussian, then applies the correlation and transforms them back to uniform. ## Support me on Patreon¶ Finally, if you enjoyed this blog post, consider supporting me on Patreon which allows me to devote more time to writing new blog posts. ## More reading¶ This post is intentionally light on math. You can find that elsewhere and will hopefully be less confused as you have a strong mental model to integrate things into. I found these links helpful: We also haven't addressed how we would actually fit a copula model. I leave that, as well as the PyMC3 implementation, as an exercise to the motivated reader ;). ## Acknowledgements¶ Thanks to Adrian Seyboldt, Jon Sedar, Colin Carroll, and Osvaldo Martin for comments on an earlier draft. Special thanks to Jonathan Ng for being a Patreon supporter. ## May 02, 2018 ### Continuum Analytics #### Anaconda’s Damian Avila on the 2017 ACM Software System Award for Jupyter I am very happy to inform you that Project Jupyter has been awarded the 2017 ACM Software System Award! As part of the Jupyter Steering Council, I am one of the official recipients of the award, but I wanted to highlight that I am just one member of a large group of people (contributors and … Read more → The post Anaconda’s Damian Avila on the 2017 ACM Software System Award for Jupyter appeared first on Anaconda. ## May 01, 2018 ### Titus Brown #### Increasing transparency in postdoc hiring and on-boarding This is a guest post from Dr. Rayna Harris. This week I started a post-doc working in Titus Brown's Data Intensive Biology lab. If there is such a thing as a dream job, this is it. I've interacted with Titus and his lab members many times through BEACON, the Marine Biological Laboratory, Software Carpentry, and Data Carpentry. One of the things I appreciate so much about Titus's style is his transparency. Here are a few of my thoughts about why interview process and the on-boarding have gone so well. ## The quick turn around Titus posted the job announcement on the Software Carpentry discuss list and on hackmd on March 15. During April, I had an interview, received an offer, accepted the offer, and set a May 1 start date. I wish all things in academia could move so fast. ## The interview questions The really cool part about the interview process what Titus posted the interview questions ahead of time here, and I submitted my responses here. This meant I could be more relaxed during the interview because the questions weren't out of the blue. Titus and his lab mates were able to ask me to delve into the details a little more or say, "cool, let's move on to the next topic". Even before Titus informed me that I would be given the interview questions ahead of time, I knew this was coming because, well, he wrote a blog post with the interview questions used for a postdoc position building pipelines. I hope to see more of this transparency and sharing of interview questions in the future. ## The salary The salary was posted with the job announcement, so I was never in doubt about what my salary would be. Additionally, in May 2016, Titus posted a blog about increasing postdoc pay. In this post, he makes it clear that he pays all his postdocs the same and that he doesn't negotiate salary. So, when he made me an offer, I didn't have to waste my energy negotiating salary, which freed up time to talk about other things that were valuable to me. ## Code of Conduct I've always liked that Titus has a Code of Conduct on his lab's website. Back in January of 2017, I was recruiting some undergrads, and I wondered if I should put a Code of Conduct on my personal website (many PIs that are affiliated with The Carpentries have one on their website, but my grad advisor did not). So, I reached out to Titus and asked him what he thought. He gave me some really good advice about how the purpose of the CoC was to convey that "these are my expectations for our behavior, and these are the paths to resolution". What I've come to realize over the past year is that even though I and many of my colleagues point to CoCs at conferences and workshops, very few of us feel equipped to responding to Code of Conduct incidents. So, I'm excited that this Friday I'll be participating in a workshop on Training for Code of Conduct Incident Response with some Carpentry Colleagues. I think this is an important step toward increasing diversity in our community. ## Communication Right now, were use Slack and GitHub for most of our communication. This means that progress on all projects is visible to the rest of the lab, and most of it is under version control. I really like both of these technologies because they work synchronously or asynchronously and collaboratively on projects and easily keep track of what's working well or not. ## Summary In the last two years, I applied for 13 different postdocs positions or jobs and had 10 interviews, but this is one is my dream job. I super excited about being in an environment with our goal is increase transparency in both our scientific methodology but also with respect to the social aspects of science. Stay tuned for more updates about our progress! --Rayna ### Matthieu Brucher #### Analog modelling: A prototype generic modeller in Python A few month ago, mystran published on KVR a small SPICE simulator for real-time processing. I liked the idea, the drawback being that the code is generic and not tailored like a static version of the optimizer. So I wondered if it was doable. But for this, I have to start from the basics and build from there. So let’s go. #### Why Python? I’ve decided to do the prototype in Python. The reason is simple, it’s easy to create something very fast in Python, write all the basic tests there and figure out what functionalities are required. First, the objective is to have a statically generated model in the long-term, so I need to differentiate between static voltage pins, input voltage pins and output voltage pins. The latter ones could be any pins for which the voltage will be computed by the modeller. Then we need components, like resistors, diodes, transistors… Capacitors and coils are also required, but let’s use the model I presented in a previous blog post. This will simplify writing the equations. So what is the basic equation in an electronic modeller? Some people use MNA, but I want something small and easy to understand, so I’ll use Kirchhoff’s current law $\sum{i_{component}} = 0$. It is simple enough and (almost) all the models I use describe current from a pin as a function of voltages. There is one thing in the prototype that is not perfect and that I haven’t figured out yet. A circuit is in a steady state when we start feeding it an audio signal. To compute it, we need to make capacitor like open circuits (easy) and coil like short circuits (not easy). The issue with short-circuits also happens when you have a variable resistor than you turn off entirely. In a dynamic model, we can easily collapse pins together when required, but in a static model, when you want to optimize the shape of the matrices, this is less than ideal. So to avoid this, I use a very small resistor. Not perfect, but it seems to work. For now. #### Description of the different methods Let’s start with the basic Modeler class (I wrote the prototype with American English and the C++ version in British English, seems like I can’t decide which one I should use…). The constructor takes a number of dynamic pins (the ones we will compute the voltage for), static pins (fixed input voltage) and input pins (variable input voltage). I will keep a list of the components of the model, then a structure for accessing the pins (useful for the dynamic pins so that we can get the sum of the currents) and the same for the state voltages. The distinction between dynamic, static and input voltages will be done through the character ‘D’, ‘S’ and ‘I’ (in Python, in C++, I’ll use an enum). We actually don’t need to store anything more than the dynamic pins, but for the sake of this prototype, let’s store all of them. class Modeler(object): """ Modeling class """ def __init__(self, nb_dynamic_pins, nb_static_pins, nb_inputs = 0): self.components = [] self.dynamic_pins = [[] for i in range(nb_dynamic_pins)] self.static_pins = [[] for i in range(nb_static_pins)] self.input_pins = [[] for i in range(nb_inputs)] self.pins = { 'D': self.dynamic_pins, 'S': self.static_pins, 'I': self.input_pins, } self.dynamic_state = np.zeros(nb_dynamic_pins, dtype=np.float64) self.static_state = np.zeros(nb_static_pins, dtype=np.float64) self.input_state = np.zeros(nb_inputs, dtype=np.float64) self.state = { 'D': self.dynamic_state, 'S': self.static_state, 'I': self.input_state, } self.initialized = False To add a new component, we need to keep the component and store the pins inside the component (because the components needs to track the pins for the current computation) and for each pin, we store the component attached to it and the index of that pin for the component. The latter functionality will allow to get the proper sign of the current for the pin when we compute our equations.  def add_component(self, component, pins): """ add a new component :param component: component to add :param pins: list of tuples indicating how the component is connected """ self.components.append(component) component.pins = pins for (i, pin) in enumerate(pins): t, pos = pin self.pins[t][pos].append((component, i)) As I’ve said, we need to compute a steady state. When we do so, we need to start by initializing components (coils and capacitors), solve for a steady state and then update the same components to update their internal state.  def setup(self): """ Initializes the internal state :param steady_state: if set to True (default), computes a steady state """ for component in self.components: component.update_steady_state(self.state, self.dt) self.solve(True) for component in self.components: component.update_steady_state(self.state, self.dt) self.initialized = True To update the state based on an input, we do the following, reusing our solve() method:  def __call__(self, input): """ Works out the value for the new input vector :param input: vector of input values """ if not self.initialized: self.setup() self.input_state[:] = input self.solve(False) for component in self.components: component.update_state(self.state) return self.dynamic_state Now we can write the solver part. We iterate several time, and for each component, we tell them to precompute their state (for costly components like diodes, transistors or valves), and then for each pin, we write an equation (remember that each pin is a state we have to solve, so with as many equations as we have pins, we should be able to get to the next state) and get the Jacobian for that equation. If the Kirchhoff equations are already satisfied (i.e. close to 0), we stop. If the delta we compute is small enough, we also stop.  def solve(self, steady_state): """ Actually solve the equation system :param steady_state: if set to True (default), computes for a steady state """ iteration = 0 while iteration < MAX_ITER and not self.iterate(steady_state): iteration = iteration + 1 def iterate(self, steady_state): """ Do one iteration :param steady_state: if set to True (default), computes for a steady state """ for component in self.components: component.precompute(self.state, steady_state) eqs = [] jacobian = [] for i, pin in enumerate(self.dynamic_pins): eq, jac = self.compute_current(pin, steady_state) eqs.append(eq) jacobian.append(jac) eqs = np.array(eqs) jacobian = np.array(jacobian) if np.all(np.abs(eqs) < EPS): return True delta = np.linalg.solve(jacobian, eqs) if np.all(np.abs(delta) < EPS): return True self.dynamic_state -= delta return False Now the last missing part will be the actual equation and Jacobian line building from the components:  def compute_current(self, pin, steady_state): """ Compute Kirschhoff law for the non static pin Compute also the jacobian for all the connected pins :param pin: tuple indicating which pin we compute the current for :param steady_state: if set to True (default), computes for a steady state """ eq = sum([component.get_current(i, self.state, steady_state) for (component, i) in pin]) jac = [0] * len(self.dynamic_state) for (component, j) in pin: for (i, component_pin) in enumerate(component.pins): if component_pin[0] == "D": jac[component_pin[1]] += component.get_gradient(j, i, self.state, steady_state) return eq, jac def retrieve_voltage(state, pin): """ Helper function to get the voltage for a given pin """ return state[pin[0]][pin[1]] Thanks to the way the modeller is built, we can pass the entire state and keep ‘D’, ‘S’ and ‘I’ to check for which voltage we need to compute the Jacobian. #### Conclusion As this blog post is already long, I’ll pause here for now before tackling the different components and what we need to change to the modeller for some ideal components like opamp. The code is available on GitHub. ## April 24, 2018 ### Matthieu Brucher #### Announcement: ATKSideChainCompressor 3.0.0 I’m happy to announce the update of ATK Side-Chain Compressor based on the Audio Toolkit and JUCE. It is available on Windows (AVX compatible processors) and OS X (min. 10.9, SSE4.2) in different formats. This update changes storage format and allows linked channels to be steered by a mix of power coming from each channel, each passing through its own attack-release filter. It enables more creative workflows with makeup gain specific to each channel. The rest of the plugin works as before, with an optional Middle/Side processing as well as side-chain working either on each channel separately or in middle/side. This plugin requires the universal runtime on Windows, which is automatically deployed with Windows update (see tis discussion on the JUCE forum). If you don’t have it installed, please check Microsoft website. ATK Side-Chain Compressor 3.0.0 The supported formats are: • VST2 (32bits/64bits on Windows, 32/64bits on OS X) • VST3 (32bits/64bits on Windows, 32/64bits on OS X) • Audio Unit (32/64bits, OS X) Direct link for ATKSideChainCompressor. The files as well as the previous plugins can be downloaded on SourceForge, as well as the source code. ## April 18, 2018 ### numfocus #### Optiver joins NumFOCUS Corporate Sponsors ## April 17, 2018 ### Continuum Analytics #### Machines Learning about Humans Learning about Machines Learning I had the great honor and pleasure of presenting the first tutorial at AnacondaCon 2018, on machine learning with scikit-learn. I spoke to a full room of about 120 enthusiastic data scientists and aspiring data scientists. I would like to thank my colleagues at Anaconda, Inc. who did such a wonderful job of organizing this … Read more → The post Machines Learning about Humans Learning about Machines Learning appeared first on Anaconda. ### Matthieu Brucher #### Book review: C++17 Quick Syntax Reference: A Pocket Guide to the Language, APIs and Library I work on a day-to-day basis on a big project that has many developers with different C++ level. Scott Meyers wrote a wonderful book on modern C++ (that I still need to review one day, especially since there is a new Effective Modern C++), but it is not for beginners. So I’m looking for that rare book with modern C++ and an explanation of good practices. #### Discussion Let’s cut to the chase right away. It’s not this book. This book is bad. Very bad. So at the core, it’s supposed to be about the syntax, but even if it was about the syntax, you can still teach the good approach, can’t you? A few examples. Templates are tackled in one of the last chapter, and so are classes. Then, the book starts almost from the beginning to tell people to use using namespace std. Is there anything more to add? Yes, there is. New and delete are tackled, then the array version is done very much further, and I’m not even talking about smart pointers. They are addressed, but so far that people think it is still good to start by not using them. Yes, talk about new/delete, but RIGHT AWAY, say that they should use std::unique_ptr, std::shared_ptr and the make_* version. It’s supposed to be about C++17, and in C++17, we avoid new/delete. OK, it is mentioned, but 2 lines after several chapters of bad practices. For range loops. They are introduced badly as well. for(auto&i: l) std::cout i std::endl; Why? Why the &? Why can’t you explain the purpose of this instead of waiting additional chapters and not even talking about when you use pass by value, pass by ref or pass by const ref? I’m still trying to figure out why it is supposed to be a syntax book, but still the author tackles smart pointers. And tuples. Why not the rest of the standard library? A good C++ book should start by presenting templates as soon as possible, the standard library and the good practices. Yes, it’s tough, but that’s why not everyone should write a C++ book. #### Conclusion The book is supposed to be about the syntax. But it lacks the good practices, with no reference to the C++ core guidelines. In the end, you still need to read another book to learn Modern C++ (hint…). ## April 16, 2018 ### Continuum Analytics #### AnacondaCON 2018 Recap: An Exploration of Modern Data Science Last year’s inaugural AnacondaCON was a major milestone for our company. Our goal was to create a conference that highlights all the different ways people are using data science and predictive analytics, and reflects the passionate and eclectic nature of our growing Python community. When over 400 people descended upon Austin to connect with peers … Read more → The post AnacondaCON 2018 Recap: An Exploration of Modern Data Science appeared first on Anaconda. ## April 12, 2018 ### Continuum Analytics #### What You Missed on Day Three of AnacondaCON 2018 And that’s a wrap! Yesterday was the third and final day of AnacondaCON 2018, and what a ride it’s been. Read some highlights from what you missed, and stay tuned for our comprehensive AnacondaCON 2018 recap, coming soon! Improving Your Anaconda Distribution User Experience Anaconda Product Manager Crystal Soja presented a roadmap of upcoming plans … Read more → The post What You Missed on Day Three of AnacondaCON 2018 appeared first on Anaconda. ### Randy Olson #### Traveling salesman portrait in Python Last week, Antonio S. Chinchón made an interesting post showing how to create a traveling salesman portrait in R. Essentially, the idea is to sample a bunch of dark pixels in an image, solve the well-known traveling salesman problem for ## April 11, 2018 ### Continuum Analytics #### What You Missed on Day Two of AnacondaCON 2018 What a day! On Tuesday we got started bright and early, then partied our way into the night. Here are some highlights from Day Two of AnacondaCON 2018. Opening Keynote: John Kim John Kim, President of HomeAway, kicked things off for us with a personal, touching keynote on Love in the Age of Machine Learning. … Read more → The post What You Missed on Day Two of AnacondaCON 2018 appeared first on Anaconda. ## April 10, 2018 ### Matthieu Brucher #### Book review: LLVM Cookbook After the book on LLVM core libraries, I want to have a look at the cookbook. #### Discussion The idea was that once I had a broad view of LLVM, I could try to apply some recipes for what I wanted to do. Let’s just say that I was deeply mistaken. First, the two authors have a very different way of writing code. One of them is… rubbish. I don’t think there is another way of saying this, but this is C++, and the guy writes C++ code as if it was C code, no class, with static states, without the override keyword. If such a guy is a professional developer, I’m sorry but I’m very scared about anything he would write professionally. The second guy is better (he uses override, for instance, so it’s very disturbing to see both styles in the same book), it’s just too bad that the code he writes seems to be just showing things existing in LLVM, but no real recipes (OK, I’m exaggerating, there are a few such examples, but the majority is “execute that command to see how LLVM does this”, and just doing “this” doesn’t have any relevance in the big picture. I suppose the only relevant and interesting parts are the first few recipes that are focused on reusing LLVM parts for a custom language. The rest is basically explanations of the later stages in a compiler. Basically what you would get from my previous review, without the explanations… #### Conclusion Have you ever read a recipe book that will explain how to prepare your kitchen for cooking instead of actually cooking recipes? This book is like that. You might learn how to use LLVM commands, but not LLVM libraries. Avoid. ## April 09, 2018 ### Continuum Analytics #### What You Missed on Day One of AnacondaCON 2018 And we’re off! Day One of AnacondaCON 2018 is officially in the books, y’all. For those of you who couldn’t make the trek to Texas, here are some highlights from what you missed today. “Why are they shooting at us?” “They’re the IT team!”The festivities kicked off this morning with a movie trailer for deep learning … Read more → The post What You Missed on Day One of AnacondaCON 2018 appeared first on Anaconda. #### Introducing the Anaconda Data Science Certification Program There is strong demand today for data science skills across all sectors of the economy. Organizations worldwide are actively looking to recruit qualified data scientists and improve the skills of their existing teams. Individuals are looking to stand out from the competition and differentiate themselves in a growing marketplace. As the creators of the world’s … Read more → The post Introducing the Anaconda Data Science Certification Program appeared first on Anaconda. #### Anaconda Debuts Data Science Certification Program Certification to Standardize Data Science Skill Set among Employers and Professionals AnacondaCON, Austin, TX—April 9, 2018 — Anaconda, the most popular Python data science platform provider, today introduced the Anaconda Data Science Certification, giving data scientists a way to verify their proficiency and organizations an independent standard for qualifying current and prospective data science experts. “The … Read more → The post Anaconda Debuts Data Science Certification Program appeared first on Anaconda. ## April 03, 2018 ### Matthieu Brucher #### Book review: Getting Started with LLVM Core Libraries LLVM has always intrigued me. Actually, I always thought about one day writing a compiler. But it was more a challenge than a requirement for any of my works, private or professional, so never dived into it. The design of LLVM was also very well thought, and probably close to something I would have had liked to create. So now the easiest is just to use LLVM for the different goals I want to achieve. I recently had to write clang-tidy rules, and I also want to perhaps create a JIT for Audio Toolkit and the modeling libraries. So lots of reasons to look at LLVM. #### Discussion The book more or less goes from C/C++ parsing to code generation. OF course, the first chapters are about setting everything up. The book using Makefiles mainly, which is not an option anymore in current LLVM versions. But it does provide the equivalent CMake version, so it is fine. Also the structure of the projects have not changed, so everything still works. Of course, lots of projects matured also over time (lld, libcxx…), so when you read that something is not yet production ready, check online (if you can find the information, I have to say that LLVM communication is very bad, just look at release notes to get an idea!). The third chapter tackles LLVM design. That’s what I liked with LLVM, the modular design, but it can also be scary because you can build more or less anything, and the API do evolve with time. But the chapter does reassure me, and helps understanding the philosophy. Then, at the fourth chapter, we start working through clang pipeline by starting with all the steps between the C/C++ code and LLVM Intermediate Representation. The AST and interaction with it are very well presented with the different stages required to generate the IR. The missing bit may be explaining why the AST is so important to have, why LLVM people had to create a new intermediate representation for this front-end. The fifth chapter is about everything we can do on the IR. I left the chapter still hungry for more. OK, the IR phases can evolve the graph, but it feels like not enough here. How does the matching actually work? This is where you can see that the book is for beginners and not for intermediate or advanced users. Also it made me realize that there is no way I can generate IR directly for my projects, I would go from a C++ AST to IR to the JIT… After working on the IR, of course, we get to code generation and the different tools in LLVM to generate either byte code or machine code and everything in-between. Lots of time is devoted to explain that this phase is very costly, as we go from something quite generic to something definitely not generic, and this part was very instructional. The seventh chapter was strange. It spent lots of time talking about a part of LLVM that was about to be removed from LLVM, the “old” JIT framework. I suppose at the time the new one was too new and some people still had to understand the old one. I still felt it was a little bit a waste of space. Cross-compilation is tackled after that, and more precisely that you may not require to do anything. This is also where one can see the limit of LLVM. To get the proper backends, you need to get the gcc toolchain. I think this is still something people do today. Even for clang 6, I actually compiled it against a gcc 7 set so that I don’t have to rebuild all the C++ third-party libraries. Also the ARM backend seemed to be broken for a long time, so that’s also not very great for trust! The last two chapters tackle tools made with clang. The first one is the static analyzer, and I have to say that I didn’t even knew it existed. There are tools with it that allow to generate HTML reports, and I liked that. But when I tried to use them with CMake, they just broke (scan_build). There is chapter about libclang and clang-tidy, which is probably my reference now. Something that wasn’t done in 2014 is that the static analyzer rules are now integrated inside clang-tidy, it’s just that it can’t build HTML reports out of them. Is it really mandatory? It gives a better view of static code issues (whereas the other rules are geared towards sugar-coating). The book ends very quickly in a small paragraph at the end of the libeling chapter. Very disturbing. #### Conclusion Despite the age of the book and the changes that went inside LLVM (clang-modernize is now part of clang-tidy, DragonEgg is… I don’t know where it went), the book seem to stay very much current (clang is still the main front-end). I would have liked more example on clang AST matchers, but I suppose it requires a full cookbook, and the audience may not be that big. Still, I’m looking forward to use the different bits to write a JIT and C++ output for electronic modeling/SPICE. ## March 30, 2018 ### Continuum Analytics #### Improved Security & Performance in Anaconda Distribution 5 We announced the release of Anaconda Distribution 5 back in October 2017, but we’re only now catching up with a blog post on the security and performance implications of that release. Improving security and enabling new language features were our primary goals, but we also reaped some performance improvements along the way. This blog post … Read more → The post Improved Security & Performance in Anaconda Distribution 5 appeared first on Anaconda. ## March 28, 2018 ### Continuum Analytics #### Anaconda Community Survey If you’re an Anaconda user, we’d love to hear from you! Please complete our short survey below, or by clicking on this link. As an extra incentive when you complete the survey you can enter a drawing to win a Sonus One Smart Speaker with Amazon Alexa. The post Anaconda Community Survey appeared first on Anaconda. ## March 27, 2018 ### numfocus #### The Worldwide Pandas Documentation Sprint: A Closer Look ## March 25, 2018 ### Leonardo Uieda #### The future of Fatiando a Terra I started developing the Fatiando a Terra Python library in 2010. Since then, many other open-source Python libraries for geophysics have appeared, each with unique capabilities. In this post, I'll explore where I think Fatiando fits in this larger ecosystem and how we can better fill our niche. ## What is Fatiando a Terra? Fatiando is a Python library for modeling and inversion in geophysics. It's composed of different subpackages: • fatiando.gridder: functions for dealing with spatial data. It's mostly used to generate point scatters or coordinate arrays for regular grids. Both are required as inputs for modeling or creating synthetic datasets. • fatiando.mesher: classes that represent geometric objects (polygons, prisms, spheres, etc) and regular meshes. These classes are used to define the geometry and physical properties of our models. They are often the inputs for gravity and magnetic modeling functions. • fatiando.vis: utilities for plotting data using matplotlib and 3D models using Mayavi. Mostly deprecated but there is a lot of useful code for displaying fatiando.mesher elements in Mayavi. • fatiando.inversion: classes for solving inverse problems. The idea is that the user needs only to implement the forward problem (the forward function and the Jacobian matrix) and the classes take care of the rest. Ideally, this would form the basis for all inversions in Fatiando. • fatiando.datasets: functions for loading data from common file formats and loading sample datasets packaged with Fatiando. • fatiando.seismic: functions and classes for modeling seismic data and some basic inversions. Mostly toy problems. • fatiando.geothermal: geothermal modeling functions. Has a single module for modeling how temperature perturbations at the surface propagate down into the Earth. • fatiando.gravmag: functions for gravity and magnetic processing, modeling, and inversion. By far the most developed package, though some components have lagged behind. ## Fatiando's niche We set out with the goal of modeling the whole Earth using all geophysical methods. Humble, right? Turns out this is extremely hard and way beyond what a couple of grad students can do in a couple of years. Back then, there were very few Python geophysical modeling libraries. A decade later, the ecosystem has expanded. The five currently on going projects of which I'm aware are (let me know in the comments if I missed any): • PyGMI: GUI + library for 3D modeling of gravity and magnetic data. • SimPEG: Forward modeling and inversion library based on the finite volume method. • pyGIMLi: Forward modeling and inversion library based on the finite element and finite volume methods. • Bruges: Modeling and processing for seismic and petrophysics. • Pyrocko: A collection of tools and libraries, mostly for seismology. The two projects that are most similar to us (SimPEG and pyGIMLi) implement flexible partial differential equation solvers that they use to run all forward modeling calculations. This makes a lot of sense because it gives them a unified framework to model most geophysical methods. It is the most sensible approach to build joint inversions of multiple geophysical datasets. However, there are some inverse problems that don't fit this paradigm, like inverting Moho relief from gravity data and some non-conventional inversion algorithms (see the animation below). It's no coincidence that Fatiando mostly contains the tools needed to implement this type of inverse problem (i.e., analytical solutions for the gravity and magnetic fields of geometric objects). This is precisely the type of research that we do at the PINGA lab. We also develop processing methods for gravity and magnetics. The niche I see for Fatiando is in gravity and magnetic methods, particularly using these analytical solutions. The processing functions are an important feature because there are hardly any open-source alternatives out there to commercial software like Oasis Montaj and Intrepid. ## The current state Fatiando has grown over the years as I slowly learned how to develop and maintain an open-source Python project. As a result, the codebase is littered with the bad choices that I made along the way. The most urgent problems that need to be fixed are: • Python 3 support. It's no longer a huge sacrifice to make the switch because all of our dependencies are supported. Actually, some of them don't even support Python 2 anymore. Support both versions is a bit of a pain and it's not worth it. The conda environments also make using multiple versions of Python easy. We should just migrate to Python 3 only and be done with it. • Test coverage is sparse and a lot of code is not maintained. There is a lot of old code in Fatiando that was included before I learned how to write good tests. As a result, they have little to no tests and are largely unused. They might be broken right now and I would have no way of knowing. We should only include code that we are willing to use and maintain. • Too many "toy problems". Mostly in the seismic package. They are useful for teaching and I don't think we need to delete all of it. But we have to be careful how we advertise these features. They shouldn't be packaged with well-tested and robust production code. • A single package. The meshing, inversion, and gridding code is not really dependent on the rest of Fatiando. There is no reason why they can't be standalone projects. This modularity might help lower the barrier for other projects to use them. Installing can still be easy by using fatiando as a metapackage (like Jupyter). ## A way forward The best way forward for Fatiando that I can see, is to become an ecosystem of specialized tools and libraries, rather than a single Python package. Having things in separate libraries allows us to better indicate what is robust and professional and what is experimental or meant as a teaching tool. In particular, the meshing library has some overlap with discretize and we should be considering a merger of our projects. Separating what we have in a library will help us articulate the requirements of Fatiando so that we can see if a merger is beneficial. We can also include experimental libraries (like fatiando.seismic.wavefd) and CLI or GUI programs as independent projects. This is how I envision the Fatiando ecosystem in the future (I have already started working on some of these projects): • fatiando: A metapackage that can be used to install all the whole stack (like the jupyter package). • deeplook: the inversion package. Should define a scikit-learn like interface and provide all of the standard tools (regularization, optimization, etc). • geometric: the geometric objects and meshes. Includes an optional way of plotting them on Mayavi and matplotlib. The way physical properties are handled needs to be redesigned and meshes need to support slicing and fancy indexing. • verde: the gridding package. It will include some new Green's functions based interpolation on which I've been working. Should also include the functions for calculating derivatives that are currently in fatiando.gravmag.transform. • harmonica: the gravity and magnetic methods package. Will port over most of the code from fatiando.gravmag. • sismica: a package for seismics and seismology. For now, will include some of the toy examples from the fatiando.seismic. • wavefd: the experimental 2D FD wave propagation code (useful for teaching but I don't trust it enough for research). • moulder: GUI for 2D gravity and magnetic modeling. All of these packages will be tied together in the fatiando Github organization and the fatiando.org website, which will include instructions for installing the entire stack. The website will also link to individual packages (as is done right now for the subpackages) and any other project in the fatiando umbrella. Members of the organization will be free to create new repositories and we'll provide a template for doing so. The requirements and goals for these new packages are: • All code will be Python 3 only. • All docstrings will use the numpy style. • Each package will have it's own docs page with tutorials, API reference, install instructions, changelog, and gallery. They will share a common template and a simple theme. • All repos will include a Code of Conduct and Contributing Guide. • All main packages will have a comprehensive test suite. Anything not tested or experimental will be moved to separate packages. Full test coverage (or as much as possible) will be a requirement for merging a contribution. This is how I think we could implement this: 1. Release Fatiando 0.6 with what we currently have in the master branch along with a note that this will be the last release to support Python 2.7. 2. Create a package template repository with the shared infrastructure (setup.py, docs, continuous integration configuration, Makefile, testing, etc). 3. Start repositories for each of the packages listed above. 4. Specify clear goals for each package and an example of how we want the API to look. 5. Focus on redesigning the inversion package first. This is the basis for many other packages. 6. Slowly copy over code from fatiando/fatiando while ensuring that everything is tested and documented. ## Help! The goal of all these changes is to make Fatiando better for users and developers by making the code more robust and well documented. I'm curious to know what the Python geophysics community thinks about all of this. Do I have it all wrong? What should be done differently? And most importantly, would you like to help? Comments? Leave one below or let me know on Twitter @leouieda. Found a typo/mistake? Send a fix through Github and I'll happily merge it (plus you'll feel great because you helped someone). All you need is an account and 5 minutes! Please enable JavaScript to view the comments powered by Disqus. ## March 23, 2018 ### Titus Brown #### Pydoit, snakemake, and workflows-as-applications Ever since Camille Scott, a grad student in the lab, developed the dammit transcriptome annotator, I've been intrigued by the design decision she made. Dammit runs a lot of other software, and Camille made the brilliant decision to avoid having dammit coordinate the execution of the dependent software itself - instead, she wrapped dammit around doit, a Python workflow library in Python. doit, like other somewhat related systems such as make, makeflow, and snakemake, specifies workflows in a declarative manner: "to reach such and such a target result, you need these intermediate results", and so on - effectively laying out a directed acyclic graph of dependencies. As part of this, these systems coordinate the execution of the commands needed to produce all of the results. And, because they have insight into the structure of the dependencies, they can do clever things like execute them in parallel, on multiple nodes, restarting failed jobs, etc. etc. By using doit, Camille was able to set up the dependency graph for the final annotated transcriptome and could then delegate the execution to the pydoit library. I myself have written many a spaghetti ball of shell commands in my time, and I was impressed with the separation of workflow logic from execution details achieved by dammit. Now, I was all set to use doit myself for some projects, but in the meantime my lab fell under the sway of my other CS grad student, Luiz Irber, who had been slowly converting people in the lab over to snakemake without me really noticing. It turns out that snakemake is much easier to dig into that doit, and between that and Luiz's wealth of knowledge (and inexorable persuasion), I ended up implementing the spacegraphcats application workflow in snakemake. And I've been pretty happy with that so far, after a few months of working with it. (More on spacegraphcats at some future point.) Now, my lab does a lot of workflow-y stuff, because we're a bioinformatics group and bioinformatics is all about running other people's software on other people's data (which is about as much fun as it sounds, but we get by). So when yet another project, the dahak metagenomics project decided to use snakemake to specify its workflows, I requested a command-line interface in the same style as spacegraphcats - but with a few extra fun twists. I wrote up a quick example in 2018-snakemake-cli, which shows a simple way to combine workflow specification with parameter specification. From the 2018-snakemake-cli README, we use run to execute snakemake workflows: ./run <workflow_file> <parameters_file>  e.g. rm -f hello.txt ./run workflow-hello params-amy  creates hello.txt with "hello amy" in it, while rm -f hello.txt ./run workflow-hello params-beth  creates hello.txt with "hello beth" in it. Here, the workflow file workflow-hello.json specifies the target hello.txt, while the parameters file params-amy parameterizes the workflow with the name "amy". Likewise, rm -f goodbye.txt ./run workflow-goodbye params-beth  will put goodbye beth in goodbye.txt. All workflows use the same set of Snakemake rules in Snakefile. ...and this is now being implemented for dahak in dahak-taco. (Warning: the dahak repos have become self aware and are replicating.) Anyway, to bring this back around to the beginning: I really like the idea of specifying workflows in a dedicated workflow engine, and then building an application around that. It means we don't have to worry about executing commands, we can tap into a large existing support community, we can make use of more powerful abstractions in our own code, and as the workflow system expands its functionality we can take advantage of it automatically. For example, snakemake seems to interface well with biocontainers and has support for Kubernetes which are both things we intend to make use of in the future. It also (in theory) makes the application much more extensible and hackable vs the traditional "I wrote my own shell command management foo" stuff I used to do. --titus ## March 21, 2018 ### Matthew Rocklin #### Dask Release 0.17.2 This work is supported by Anaconda Inc. and the Data Driven Discovery Initiative from the Moore Foundation. I’m pleased to announce the release of Dask version 0.17.2. This is a minor release with new features and stability improvements. This blogpost outlines notable changes since the 0.17.0 release on February 12th. You can conda install Dask: conda install dask  or pip install from PyPI: pip install dask[complete] --upgrade  Full changelogs are available here: Some notable changes follow: ### Tornado 5.0 Tornado is a popular framework for concurrent network programming that Dask relies on heavily. Tornado recently released a major version update that included both some major features for Dask as well as a couple of bugs. The new IOStream.read_into method allows Dask communications (or anyone using this API) to move large datasets more efficiently over the network with fewer copies. This enables Dask to take advantage of high performance networking available on modern super-computers. On the Cheyenne system, where we tested this, we were able to get the full 3GB/s bandwidth available through the Infiniband network with this change (when using a few worker processes). Many thanks to Antoine Pitrou and Ben Darnell for their efforts on this. At the same time there were some unforeseen issues in the update to Tornado 5.0. More pervasive use of bytearrays over bytes caused issues with compression libraries like Snappy and Python 2 that were not expecting these types. There is a brief window in distributed.__version__ == 1.21.3 that enables this functionality if Tornado 5.0 is present but will misbehave if Snappy is also present. ### HTTP File System Dask leverages a file-system-like protocol for access to remote data. This is what makes commands like the following work: import dask.dataframe as dd df = dd.read_parquet('s3://...') df = dd.read_parquet('hdfs://...') df = dd.read_parquet('gcs://...')  We have now added http and https file systems for reading data directly from web servers. These also support random access if the web server supports range queries. df = dd.read_parquet('https://...')  As with S3, HDFS, GCS, … you can also use these tools outside of Dask development. Here we read the first twenty bytes of the Pandas license: from dask.bytes.http import HTTPFileSystem http = HTTPFileSystem() with http.open('https://raw.githubusercontent.com/pandas-dev/pandas/master/LICENSE') as f: print(f.read(20))  b'BSD 3-Clause License'  Thanks to Martin Durant who did this work and manages Dask’s byte handling generally. See remote data documentation for more information. ### Fixed a correctness bug in Dask dataframe’s shuffle We identified and resolved a correctness bug in dask.dataframe’s shuffle that resulted in some rows being dropped during complex operations like joins and groupby-applies with many partitions. See dask/dask #3201 for more information. ### Cluster super-class and intelligent adaptive deployments There are many Python subprojects that help you deploy Dask on different cluster resource managers like Yarn, SGE, Kubernetes, PBS, and more. These have all converged to have more-or-less the same API that we have now combined into a consistent interface that downstream projects can inherit from in distributed.deploy.Cluster. Now that we have a consistent interface we have started to invest more in improving the interface and intelligence of these systems as a group. This includes both pleasant IPython widgets like the following: as well as improved logic around adaptive deployments. Adaptive deployments allow clusters to scale themselves automatically based on current workload. If you have recently submitted a lot of work the scheduler will estimate its duration and ask for an appropriate number of workers to finish the computation quickly. When the computation has finished the scheduler will release the workers back to the system to free up resources. The logic here has improved substantially including the following: • You can specify minimum and maximum limits on your adaptivity • The scheduler estimates computation duration and asks for workers appropriately • There is some additional delay in giving back workers to avoid hysteresis, or cases where we repeatedly ask for and return workers Some news from related projects: • The young daskernetes project was renamed to dask-kubernetes. This displaces a previous project (that had not been released) for launching Dask on Google Cloud Platform. That project has been renamed to dask-gke. • A new project, dask-jobqueue was started to handle launching Dask clusters on traditional batch queuing systems like PBS, SLURM, SGE, TORQUE, etc.. This projet grew out of the Pangeo collaboration • A Dask Helm chart has been added to Helm’s stable channel ## Acknowledgements The following people contributed to the dask/dask repository since the 0.17.0 release on February 12h: • Anderson Banihirwe • Dan Collins • Dieter Weber • Gabriele Lanaro • John Kirkham • James Bourbeau • Julien Lhermitte • Matthew Rocklin • Martin Durant • Max Epstein • nkhadka • okkez • Pangeran Bottor • Rich Postelnik • Scott M. Edenbaum • Simon Perkins • Thrasibule • Tom Augspurger • Tor E Hagemann • Uwe L. Korn • Wes Roach The following people contributed to the dask/distributed repository since the 1.21.0 release on February 12th: • Alexander Ford • Andy Jones • Antoine Pitrou • Brett Naul • Joe Hamman • John Kirkham • Loïc Estève • Matthew Rocklin • Matti Lyra • Sven Kreiss • Thrasibule • Tom Augspurger ## March 20, 2018 ### Fabian Pedregosa #### Notes on the Frank-Wolfe algorithm, Part I \def\xx{\boldsymbol x} \def\yy{\boldsymbol y} \def\ss{\boldsymbol s} \def\dd{\boldsymbol d} \DeclareMathOperator*{\argmin}{{arg\,min}} \DeclareMathOperator*{\minimize}{{minimize}} \DeclareMathOperator*{\diam}{{diam}} 

This blog post is the first in a series discussing different theoretical and practical aspects of the Frank-Wolfe algorithm.

### Matthieu Brucher

#### Writing custom checks for clang-tidy

I started taking a heavier interest in clang-tidy a few months ago, as I was looking at static analyzers. I found at the time that it was quite complicated to work on clang internal AST. It is a wonderful tool, but it is also a very complex one. Thankfully, the cfe-dev mailing list is full of nice people.

I also started my journey in the LLVM/clang land with the help of this blog post.

# Quick setup

The previous blog post is very great to explain how to setup a build:

git clone http://llvm.org/git/llvm.git
cd llvm/tools/
git clone http://llvm.org/git/clang.git
cd clang/tools/
git clone https://github.com/mbrucher/clang-tools-extra extra

cd ../../../
mkdir build && cd build/
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo ..
make check-clang-tools

A new checker can be created with the following command line:

./add_new_check.py misc catch-by-const-ref

A new folder can easily be created manually, and each checker consists of two sections:

1. A matcher that will select AST sections
2. A checker that will add additional checks on top of the matcher, like macro or file

Now let’s try to implement two rules:

• The first one will check that we catch exceptions by const ref (a good practice)
• The second will allow functions detections (C functions that are now replaced by C++, or functions that should be replaced by safer ones).

# A simple matcher for catching by const ref

The best reference for the matchers in clang is (unfortunately) the doxygen for the last_matcher namespace. As you can see, it is quite difficult to navigate, but it’s not as complicated.

• A variable declaration
• Inside a catch statement
• That is a reference
• But not const

My first trial was to match all catch statement. This is easily done by using cxxCatchStmt. When I did that, the issue that I could check that the variable underneath was declared const or not. So instead, I asked some help from the cfe-dev people.

So let’s start over again. This is what we need:

• variable declaration is matched with varDecl (for a type VarDecl, notice the case difference)
• inside a catch statement is matched by isExceptionVariable
• a reference type is matched by references
• and the const aspect is matched by isConstQualified

varDecl is an instance of VariadicDynCastAllOfMatcher that matches VarDecl. It can take several parameters. So the first parameter will be isExceptionVariable. The second will describe that type of access we are looking for hasType(references(qualType(unless(isConstQualified())))). If you unroll this match, we are looking for a reference on a qualifier type that is not (unless) const qualified.

The result is then:

1. void CatchByConstRefCheck::registerMatchers(MatchFinder *Finder) {
2.   // This is a C++ only check thus we register the matchers only for C++
3.   if (!getLangOpts().CPlusPlus)
4.     return;
5. 
6.   Finder->addMatcher(varDecl(isExceptionVariable(),hasType(references(qualType(unless(isConstQualified()))))).bind("catch"), this);
7. }

Now that we have a good matcher, the checker is easy to write. We want to warn for all these variables, and we can even easily propose a fix.

1. void CatchByConstRefCheck::check(const MatchFinder::MatchResult &Result) {
2. 
3.   const VarDecl* varCatch = Result.Nodes.getNodeAs<VarDecl>("catch");
4. 
5.   const char *diagMsgCatchReference = "catch handler catches by non const reference; "
6.                                         "catching by const-reference may be more efficient";
7. 
8.   // Emit error message if the type is not const (ref)s
9.   diag(varCatch->getLocStart(), diagMsgCatchReference)
10.     << FixItHint::CreateInsertion(varCatch->getLocStart(), "const ");
11. }

Of course, I’ve written a few examples that are tested by clang testing framework (make check-clang-tools).

# Using check options for matching deprecated functions

Now, for a second rule, I wanted to detect some C functions that have a C++ equivalent. For instance, exp() should be replaced by std::exp(), or fabs() by std::abs(). As the list can be different for different projects (and as you may want to replace other functions by others).

When using options, there are two things to do. First getting the options in the constructor, and also use a store call:

1. DetectCFunctionsCheck::DetectCFunctionsCheck(StringRef Name, ClangTidyContext *Context)
2.     : ClangTidyCheck(Name, Context),
3.       stdNamespaceFunctions(Options.get("stdNamespaceFunctions", "floor,exp")),
4.       functionsToChange(Options.get("functionsToChange", "fabs>std::abs"))
5. {
6.     parseStdFunctions();
7.     parseFunctionToChange();
8. }
9. 
10. void DetectCFunctionsCheck::storeOptions(ClangTidyOptions::OptionMap &Opts)
11. {
12.   Options.store(Opts, "stdNamespaceFunctions", stdNamespaceFunctions);
13.   Options.store(Opts, "functionsToChange", functionsToChange);
14. }

I have two calls here to parse the option strings. They are in charge of splitting them at ‘,’ and then for the replacement functions, we split them at ‘>’. Here, the default options are very simple, and it is easy to change it.

The matchers are very similar:

1. void DetectCFunctionsCheck::registerMatchers(MatchFinder *Finder) {
2.     // Should check if there are duplicates.
3.     for(auto fun: stdNamespaceFunctionsSet)
4.     {
5.       Finder->addMatcher(callExpr(callee(functionDecl(allOf(hasName(fun), unless(cxxMethodDecl()), hasParent(translationUnitDecl()))))).bind(fun), this);
6.     }
7.     for(auto fun: functionsToChangeMap)
8.     {
9.       Finder->addMatcher(callExpr(callee(functionDecl(allOf(hasName(fun.first), unless(cxxMethodDecl()), hasParent(translationUnitDecl())))).bind(fun.first), this);
10.     }
11. }

So we select call expression that use a function whose name contains the name required, that is not a call to a method and that the parent of the call is the translation unit a.k.a. the global namespace (one could use namespace here if the function was to be in a namespace). Then the check is very easy as well as the fix-it hint:

1. 
2. void DetectCFunctionsCheck::check(const MatchFinder::MatchResult &Result) {
3. 
4.     for(const auto& fun: stdNamespaceFunctionsSet)
5.     {
6.         const CallExpr* call = Result.Nodes.getNodeAs<CallExpr>(fun);
7.         if(call)
8.         {
9.             diag(call->getLocStart(), "this function has a corresponding std version. Consider using it (std::" + fun + ")")
10.                 << FixItHint::CreateInsertion(call->getLocStart(), "std::");
11.         }
12.     }
13.     for(const auto& fun: functionsToChangeMap)
14.     {
15.         const CallExpr* call = Result.Nodes.getNodeAs<CallExpr>(fun.first);
16.         if(call)
17.         {
18.             auto start = call->getLocStart();
19.             diag(start, "this function has a better version. Consider using it (" + fun.second + ")")
20.                 << FixItHint::CreateReplacement(SourceRange(start, start.getLocWithOffset(fun.first.size() - 1)), fun.second);
21.         }
22.     }
23. }

It would be easy to add a third category, for instance for C unsafe functions, but I don’t need this for now.

I have additional functional tests as well in the repository.

# Conclusion

I like writing rules, as clang-tidy is very powerful. Unfortunately, it is sometimes difficult to figure out what query you want to write. Although clang-query helps on this a lot, it is not very nice to use (there is no history of previous rules, you can’t go back on the same line…). I suppose dumping the AST helps as you can figure out what is the match you really want.

These two rules are available on github.

### Matthew Rocklin

#### Summer Student Projects 2018

Around this time of year students look for Summer projects. Often they get internships at potential future employers. Sometimes they become more engaged in open source software.

This blogpost contains some projects that I think are appropriate for a summer student in a computational field. They reflect my biases (which, assuming you read my blog, you’re ok with) and are by no means comprehensive of opportunities within the Scientific Python ecosystem. To be perfectly clear I’m only providing ideas and context here, I offer neither funding nor mentorship.

### Criteria for a good project

1. Is well defined and tightly scoped to reduce uncertainty about what a successful outcome looks like, and to reduce the necessity for high-level advising
2. Is calibrated so that an industrious student can complete it in a few months
3. It’s useful, but also peripheral. It has value to the ecosystem but is not critical enough that a core devs is likely to complete the task in the next few months, or be overly picky about the implementation.
4. It’s interesting, and is likely to stimulate thought within the student
5. It teaches valuable skills that will help the student in a future job search
6. It can lead to future work, if the student makes a strong connection

The projects listed here target someone who already has decent knowledge of the fundamentals PyData or SciPy ecosystem (numpy, pandas, general understanding of programming, etc..). They are somewhat focused around Dask and other projects that I personally work on.

### Distributed GPU NDArrays with CuPy, Bohrium, or other

Dask arrays coordinate many NumPy arrays to operate in parallel. It includes all of the parallel algorithms, leaving the in-memory implementation to NumPy chunks.

But the chunk arrays don’t actually have to be NumPy arrays, they just have to look similar enough to NumPy arrays to fool Dask Array. We’ve done this before with sparse arrays which implement a subset of the numpy.ndarray API, but with sparse storage, and it has worked nicely.

There are a few GPU NDArray projects out there that satisfy much of the NumPy interface:

It would be valuable to do the same thing with Dask Array with them. This might give us a decent general purpose distributed GPU array relatively cheaply. This would engage the following:

1. Knowledge of GPUs and performance implications of using them
2. NumPy protocols (assuming that the GPU library will still need some changes to make it fully compatible)
3. Distributed performance, focusing on bandwidths between various parts of the architecture
4. Profiling and benchmarking

### Use Numba and Dask for Numerical Simulations

While Python is very popular in data analytics it has been less successful in hard-core numeric algorithms and simulation, which are typically done in C++/Fortran and MPI. This is because Python is perceived to be too slow for serious numerical computing.

Yet with recent advances in Numba for fast in-core computing and Dask for parallel computing things may be changing. Certainly fine-tuned C++/Fortran + MPI can out-perform Numba and Dask, but by how much? If the answer is only 10% or so then it could be that the lower barrier to entry of Numba, or the dynamic scaling of Dask, can make them competitive in fields where Python has not previously had a major impact.

For which kinds of problems is a dynamic JITted language almost-as-good as C++/MPI? For which kinds of problems is the dynamic nature of these tools valuable, either due to more rapid development, greater flexibility in accepting community created modules, dynamic load balancing, or other reasons?

This project would require the student to come in with an understanding of their own field, the kinds of computational problems that are relevant there, and an understanding of the performance characteristics that might make dynamic systems tolerable. They would learn about optimization and profiling, and would characterize the relevant costs of dynamic languages in a slightly more modern era.

### Blocked Numerical Linear Algebra

Dask arrays contain some algorithms for blocked linear algebra, like least squares, QR, LU, Cholesky, etc.., but no particular attention has been paid to them.

It would be interesting to investigate the performance of these algorithms and compare them to proper distributed BLAS/LAPACK implementations. This will very likely lead to opportunities to improve the algorithms and possibly some of Dask’s internal machinery.

Someone with understanding of R’s or Julia’s networking stack could adapt Dask’s distributed scheduler for those languages. Recall that the dask.distributed network consists of a central scheduler, many distributed workers, one or more user-facing clients. Currently these are all written in Python and only really useful from that language.

Making this system useful in another language would require rewriting the client and worker code, but would not require rewriting the scheduler code, which is intentionally language agnostic. Fortunately the client and worker are both relatively simple codebases (relative to the scheduler at least) and minimal implementations could probably be written in around 1-2k lines each.

This would not provide the high-level collections like dask.array or dask.dataframe, but would provide all of the distributed networking, load balancing, resilience, etc.. that is necessary to build a distributed computing stack. It would also allow others to come later and build the high level collections that would be appropriate for that language (presumably R and Julia user communities don’t want exactly Pandas-style dataframe semantics anyway).

This is discussed further in dask/distributed #586 and has actually been partially implemented in Julia in the Invenia project.

This would require some knowledge of network programming and, ideally, async programming in either R or Julia.

### High-Level NumPy Optimizations

Projects like Numpy and Dask array compute what the user says, even if a more efficient solution exists.

(x + 1)[:5]  # what user said

x[:5] + 1    # faster and equivalent solution


It would be useful to have a project that exactly copies the Numpy API, but constructs a symbolic representation of that computation instead of performs work. This would enable a few important use cases that we’ve seen arise recently. These include both applications from just analyzing the symbolic representation and also applications from changing it to a more optimal form:

1. You could analyze this representation and warn users about intermediate stages that require a lot of RAM or compute time
2. You could suggest ideal chunking patterns based on the full computation
3. You could communicate this computation over the network to a remote server to perform the computation
4. You could visualize the computation to help users or students understand what they’re computing
5. You could manipulate the representation into more efficient forms (such as what is shown above)

The first part of this would be to construct a class that behaves like a Numpy array but constructs a symbolic tree representation instead. This would be similar to Sympy, Theano, Tensorflow, Blaze.expr or similar projects, but it would have much smaller scope and would not be at all creative in designing new APIs. I suspect that you could bootstrap this project quickly using systems like dask.array, which already do all of the shape and dtype computations for you. This is also a good opportunity to connect to recent and ongoing work in Numpy to establish protocols that allow other array libraries (like this one) to work smoothly with existing Numpy code.

Then you would start to build some of the analyses listed above on top of this representation. Some of these are harder than others to do robustly, but presumably they would get easier in time.

## March 19, 2018

### Continuum Analytics

#### Anaconda included in Gartner’s 2018 Magic Quadrant for Data Science and Machine Learning Platforms

Gartner recently released its 2018 Magic Quadrant for Data Science and Machine Learning Platforms, featuring Anaconda for the first time. For those unfamiliar with the process, vendors complete an extensive survey (150+ questions) and submit financial data and customer references to Gartner for evaluation. There’s a qualification bar based on revenue and customer traction, and …

## March 18, 2018

### Titus Brown

#### My approach to community building and coordination

For the last three months I've been knee-deep (neck deep? thoroughly underwater?) in the #CommonsPilot project, where I have been funded to take on a community coordinating role.

Someone asked today about how my coordination approach dovetails with the immense complexity of the project, and I put together the following answer, which I liked, and am now sharing with y'all.

I am trying to use the following process:

• put in place some loose guidelines (we'll be using this platform for e-mail, that project for documents, etc.);

• define a community code of conduct, and start things off the way you want to continue with communication;

• devise some simple on-boarding to connect people with guidelines;

• watch carefully to see what communication avenues are actually being used / work well (slack has been a success, google calendar... not so much); fine tune accordingly (we're now using groups.io for both mailing lists and calendars);

• then, observe & extract the emergent "Desire Paths" and bring them into the on-boarding docs ;

• layer more structure on as need becomes apparent, but don't do it too early, because each layer of structure acts as a straitjacket on the project and limits flexibility and adaptation;

• use training and in-person / 1-1 meetings to inculcate culture and process;

• iterate!

This process has emerged from my participation in open source projects over the last 30 years, as well as from watching Greg Wilson grow Software Carpentry from scratch over a decade. It is as different from the way academics think about building collaborations as the Carpentry teaching method is from "sage on a stage"-style teaching :).

--titus

p.s. I just started taking scuba lessons (PADI Open Water cert), which may have been a subconscious reaction to this #CommonsPilot thing... "breathe deeply and slowly. don't panic. and when your air runs out? bail to the surface." :)

## March 15, 2018

### Continuum Analytics

#### March 2018 Kubernetes Security Vulnerabilities and Anaconda Enterprise

The Anaconda team tracks security vulnerabilities and CVEs via the National Vulnerability Database (NVD) on an ongoing basis. Our team is committed to the security of Anaconda Enterprise by making updates available in a timely manner in response to security vulnerabilities and similar incidents. Two security vulnerabilities (CVE-2017-1002101 and CVE-2017-1002102) were recently identified in Kubernetes, which …

### Leonardo Uieda

#### A template for reproducible papers

At the PINGA lab, we have been experimenting with ways to increase the reproducibility of our research by publishing the git repositories that accompany our papers. You can find them on our Github organzation. I've synthesized the experience of the last 4 years into a template in the pinga-lab/paper-template repository.

The template reflects the tools we've been using and the type of research that we do:

• Most papers are proposing a new methodology rather than the analysis of a dataset.
• There is always an application to a dataset to show the method works. We can't always publish the data but we include it in the repository whenever we can.
• All papers include an implementation of the proposed method.
• Our code is usually written in Python and executed in Jupyter notebooks.
• The focus of the paper is usually on the methodology, not the code. As such, the code is more of a proof-of-concept than a full blown application or library.
• The paper itself is written in LaTeX with the source usually included in the repository.

This certainly won't fit everyone's needs but I hope that you can at least use a few bits and pieces for inspiration. Of course, the template code is open-source (BSD license) and you are free to reuse it however you like. The template includes a sample application to climate change data, complete with a Python package, automated tests, an analysis notebook, a notebook that generates the paper figure, raw data, and a LaTeX text. Everything, from compilation to building the final PDF, can be done with a single make command.

We've been using different versions of this template for a few years and I've been tweaking it to address some of the difficulties we encountered along the way.

• Running experiments in Jupyter notebooks can get messy when people aren't diligent about the execution order. It can be hard to remember to "Reset and run all" before using the results.
• The execution was done manually so you had to remember and document in what order the notebooks need to be run.
• Experimental parameters (e.g., number of data points, inversion parameters, model configuration) were copied into the text manually. This sometimes led to values getting out of sync between the notebooks and paper.
• We only had integration tests implemented in notebooks. More often than not, the checks were visual and not automated. I think a big reason for this is the lack of experience in writing tests within the group and setting up all of the testing infrastructure (mainly how to use pytest and what kind of test to perform).

The latest update addresses all of these pain points. The main features of the new template are:

• Uses Makefiles to automate the workflow. You can build and test the software, generate results and figures, and compile the PDF with a single make command.
• A Makefile for building the manuscript PDF with extra rules for running proselint, counting words, and opening the PDF.
• A starter conda environment for managing dependencies and making sure everyone gets the same version of the dependencies.
• A Makefile for building the Python package, testing it with pytest, running static code checks (flake8 and pylint), and generating results and figures from the notebooks.
• The code Makefile can run the notebooks using jupyter nbconvert to guarantee that the notebooks are executed in sequential order (top to bottom). I would love to use nbflow but the SCons requirement puts me off a bit. make works fine and the basic syntax is easier to understand.
• An example of using code to write experimental parameters in a .tex file. The file defines new variables that are used in the main text. This guarantees that the values cited in the text are the ones that you actually used to produce the results.

This last feature is my favorite. For example, the notebook code/notebooks/estimate-hawaii-trend.ipynb has the following code:

tex = r"""
% Generated by code/notebooks/estimate-hawaii-trend.ipynb
\newcommand{{\HawaiiLinearCoef}}{{{linear:.3f} C}}
\newcommand{{\HawaiiAngularCoef}}{{{angular:.3f} C/year}}
""".format(linear=trend.linear_coef, angular=trend.angular_coef)

with open('../../manuscript/hawaii_trend.tex', 'w') as f:
f.write(tex)


It defines the LaTeX commands \HawaiiLinearCoef and \HawaiiAngularCoef that can be used in the paper to insert the values estimated by the Python code. The commands are saved to a .tex file that can be included in the main manuscript.tex. Since this file is generated by the code, the values are guaranteed to be up-to-date.

If you want to use the template to start a new project:

1. Create a new git repository:

mkdir mypaper
cd mypaper
git init

2. Pull in the template code:

git pull https://github.com/pinga-lab/paper-template.git master

3. Create a new repository on Github.

4. Push the template code to Github:

git remote add origin https://github.com/USER/REPOSITORY.git
git push -u origin master

5. Follow the instruction in the README.md.

Alternatively, you can use the "Import repository" option on Github.

I hope that this template will be useful to people outside of our lab. There is definitely still room for improvement and I'm looking forward to trying it out on my next project.

What other features would you like to see in the template? Let me know in the comments (or better yet, submit a pull request). I'd love to know about your experiences and workflows for computational papers.

Found a typo/mistake? Send a fix through Github and I'll happily merge it (plus you'll feel great because you helped someone). All you need is an account and 5 minutes!

## March 13, 2018

### Matthieu Brucher

#### Compile last Audio Toolkit on Bela with Clang

More than a year ago, I started playing with the Bela board. At the time, I had issues compiling Audio ToolKit with clang. The issue was that the gcc shipped with the Debian image the BeagleBoard used was too old and didn’t fully support C++11. The one that ships now is GCC 6, which is even C++14 compliant. Meaning that everything is available to build Audio Toolkit with Python support.

# Setting up Bela

Starting from a fresh image, the main things to install are:

• Boost
• FFTW
• Python and Numpy

With the BeagleBoard, it’s easy as one apt-get line:

apt-get install python3-dev python3-numpy python3-scipy python3-nose libfftw3-dev libboost-dev libboost-system1.62-dev libboost-test1.62-dev

And one line to install nosetests:
pip3 install nosetests

After all the dependent packages are downloaded, the git repository can be cloned:

git clone https://github.com/mbrucher/AudioTK.git
git submodule init
git submodule update

# Direct build

Let’s create a new folder named AudioTK-build on the same level as AudioTK. We can then run cmake from it:

cmake ../AudioTK

Once this is done, let’s build ATK:

make

It will take some time, but then we can run the tests. First, we want to export the building Python path to be able to test in place before the install step.
export PYTHONPATH=/root/local/src/AudioTK-build/Python/:\$PYTHONPATH

And then:

make test

The result should look something like this:

Test project /root/local/src/AudioTK-build Start 1: Adaptive 1/23 Test #1: Adaptive ......................... Passed 9.54 sec Start 2: Core 2/23 Test #2: Core ............................. Passed 481.68 sec Start 3: Delay 3/23 Test #3: Delay ............................ Passed 168.64 sec Start 4: Distortion 4/23 Test #4: Distortion ....................... Passed 0.50 sec Start 5: Dynamic 5/23 Test #5: Dynamic .......................... Passed 23.90 sec Start 6: EQ 6/23 Test #6: EQ ............................... Passed 158.12 sec Start 7: IO 7/23 Test #7: IO ............................... Passed 0.66 sec Start 8: Mock 8/23 Test #8: Mock ............................. Passed 2.98 sec Start 9: Preamplifier 9/23 Test #9: Preamplifier ..................... Passed 1.45 sec Start 10: PyAdaptive 10/23 Test #10: PyAdaptive ....................... Passed 10.51 sec Start 11: PyCore 11/23 Test #11: PyCore ........................... Passed 6.26 sec Start 12: PyDelay 12/23 Test #12: PyDelay .......................... Passed 5.78 sec Start 13: PyDistortion 13/23 Test #13: PyDistortion ..................... Passed 7.13 sec Start 14: PyDynamic 14/23 Test #14: PyDynamic ........................ Passed 16.39 sec Start 15: PyEQ 15/23 Test #15: PyEQ ............................. Passed 9.83 sec Start 16: PyPreamplifier 16/23 Test #16: PyPreamplifier ................... Passed 13.20 sec Start 17: PyReverberation 17/23 Test #17: PyReverberation .................. Passed 4.45 sec Start 18: PySpecial 18/23 Test #18: PySpecial ........................ Passed 4.41 sec Start 19: PyTools 19/23 Test #19: PyTools .......................... Passed 5.79 sec Start 20: Reverberation 20/23 Test #20: Reverberation .................... Passed 12.18 sec Start 21: Special 21/23 Test #21: Special .......................... Passed 1295.59 sec Start 22: Tools 22/23 Test #22: Tools ............................ Passed 13.43 sec Start 23: Utility 23/23 Test #23: Utility .......................... Passed 0.13 sec

100% tests passed, 0 tests failed out of 23

Obviously, this is very slow. It’s more or less 50 times slower than the same on my old MacBook Pro!

# Conclusion

Clearly I’m not in a place where I can use ATK on the BeagleBoard. While looking at the assembler code, it seems that almost no Neon instructions were generated.

So the next entry in this series will tackle optimizing ATK on ARM!

## March 09, 2018

### Leonardo Uieda

#### Podcasts in my playlist (2018 edition)

Last year, I posted my podcast playlist in response to a similar post by John Leeman (of Don't Panic Geocast fame). In a recent episode (maybe episode 158), John asked listeners for an updated list of recommendations. Here are mine.

I'll start with the new additions since last year, then the ones that stayed with me throughout 2017, and finally the ones that I'm looking to get started this year.

• Gastropod: A podcast that "looks at food through the lens of science and history". In each episode, the hosts dive deep into the science behind a type of food/process/ingredient and how it became what it is today. One of my favorite episodes is about koji, the fungus behind sake, miso, shoyu, and more.
• The Unmade Podcast: A podcast about insane ideas for new podcasts. Very meta and silly but a fun way to pass the time and get a few laughs.
• We Martians: A podcast all about the science and exploration of Mars. Just listened to a few episodes but I'm enjoying it so far.

The survivors:

• Don't Panic Geocast: All things geoscience (sometimes with very interesting guests).
• Hello Internet: A light conversation between two friends who make science videos on YouTube with a surprisingly common discussion of flags.
• Imaginary Worlds: "A show about how we create them and why we suspend our disbelief". Still one of my favorites.
• Invisibilia: A series about the forces that shape our lives. Also one of my favorites.
• Talk Python To Me: The title pretty much says it all.
• Radiolab: Interesting stories about all sorts of topics. Very high quality production.

The ones I haven't tried yet:

• Fieldwork Diaries: Interviews with scientists about their field experiences.
• Ologies: Each episode is about a different field of knowledge. I think it's based on an idea from the Unmade Podcast.
• The Truth: "Movies for your ears".

That's it for my list. Do you have any recommendations?

Found a typo/mistake? Send a fix through Github and I'll happily merge it (plus you'll feel great because you helped someone). All you need is an account and 5 minutes!

## March 06, 2018

### Continuum Analytics

#### Anaconda Repository Changes Afoot

In August 2017, Continuum Analytics announced it is now Anaconda, Inc. Here at Anaconda, we are all excited about the change, and have spent the last several months switching everything over to the Anaconda name. One of the last big changes we need to make is to switch our default conda repository from https://repo.continuum.io to …

## February 28, 2018

### Matthew Rocklin

#### Craft Minimal Bug Reports

Following up on a post on supporting users in open source this post lists some suggestions on how to ask a maintainer to help you with a problem.

You don’t have to follow these suggestions. They are optional. They make it more likely that a project maintainer will spend time helping you. It’s important to remember that their willingness to support you for free is optional too.

Crafting minimal bug reports is essential for the life and maintenance of community-driven open source projects. Doing this well is an incredible service to the community.

## Minimal Complete Verifiable Examples

I strongly recommend following Stack Overflow’s guidelines on Minimal Complete Verifiable Exmamples. I’ll include brief highlights here:

… code should be …

• Minimal – Use as little code as possible that still produces the same problem
• Complete – Provide all parts needed to reproduce the problem
• Verifiable – Test the code you’re about to provide to make sure it reproduces the problem

Lets be clear, this is hard and takes time.

As a question-asker I find that creating an MCVE often takes 10-30 minutes for a simple problem. Fortunately this work is usually straightforward, even if I don’t know very much about the package I’m having trouble with. Most of the work to create a minimal example is about removing all of the code that was specific to my application, and as the question-asker I am probably the most qualified person to do that.

When answering questions I often point people to StackOverflow’s MCVE document. They sometimes come back with a better-but-not-yet-minimal example. This post clarifies a few common issues.

As an running example I’m going to use Pandas dataframe problems.

## Don’t post data

You shouldn’t post the file that you’re working with. Instead, try to see if you can reproduce the problem with just a few lines of data rather than the whole thing.

Having to download a file, unzip it, etc. make it much less likely that someone will actually run your example in their free time.

### Don’t

I’ve uploaded my data to Dropbox and you can get it here: my-data.csv.gz

import pandas as pd


### Do

You should be able to copy-paste the following to get enough of my data to cause the problem:

import pandas as pd
df = pd.DataFrame({'account-start': ['2017-02-03', '2017-03-03', '2017-01-01'],
'client': ['Alice Anders', 'Bob Baker', 'Charlie Chaplin'],
'balance': [-1432.32, 10.43, 30000.00],
'db-id': [1234, 2424, 251],
'proxy-id': [525, 1525, 2542],
'rank': [52, 525, 32],
...
})


## Actually don’t include your data at all

Actually, your data probably has lots of information that is very specific to your application. Your eyes gloss over it but a maintainer doesn’t know what is relevant and what isn’t, so it will take them time to digest it if you include it. Instead see if you can reproduce your same failure with artificial or random data.

### Don’t

Here is enough of my data to reproduce the problem

import pandas as pd
df = pd.DataFrame({'account-start': ['2017-02-03', '2017-03-03', '2017-01-01'],
'client': ['Alice Anders', 'Bob Baker', 'Charlie Chaplin'],
'balance': [-1432.32, 10.43, 30000.00],
'db-id': [1234, 2424, 251],
'proxy-id': [525, 1525, 2542],
'rank': [52, 525, 32],
...
})


### Do

My actual problem is about finding the best ranked employee over a certain time period, but we can reproduce the problem with this simpler dataset. Notice that the dates are out of order in this data (2000-01-02 comes after 2000-01-03). I found that this was critical to reproducing the error.

import pandas as pd
df = pd.DataFrame({'account-start': ['2000-01-01', '2000-01-03', '2000-01-02'],
'db-id': [1, 2, 3],
'name': ['Alice', 'Bob', 'Charlie'})


As we shrink down our example problem we often discover a lot about what causes the problem. This discovery is valuable and something that only the question-asker is capable of doing efficiently.

## See how small you can make things

To make it even easier, see how small you can make your data. For example if working with tabular data (like Pandas), then how many columns do you actually need to reproduce the failure? How many rows do you actually need to reproduce the failure? Do the columns need to be named as you have them now or could they be just “A” and “B” or descriptive of the types within?

### Do

import pandas as pd
df = pd.DataFrame({'datetime': ['2000-01-03', '2000-01-02'],
'id': [1, 2]})


## Remove unnecessary steps

Is every line in your example absolutely necessary to reproduce the error? If you’re able to delete a line of code then please do. Because you already understand your problem you are much more efficient at doing this than the maintainer is. They probably know more about the tool, but you know more about your code.

### Don’t

The groupby step below is raising a warning that I don’t understand

df = pd.DataFrame(...)

df = df[df.value > 0]
df = df.fillna(0)

df.groupby(df.x).y.mean()  # <-- this produces the error


### Do

The groupby step below is raising a warning that I don’t understand

df = pd.DataFrame(...)

df.groupby(df.x).y.mean()  # <-- this produces the error


## Use Syntax Highlighting

When using Github you can enclose code blocks in triple-backticks (the character on the top-left of your keyboard on US-standard QWERTY keyboards). It looks like this:

python
x = 1



## Provide complete tracebacks

You know all of that stuff between your code and the exception that is hard to make sense of? You should include it.

### Don’t

I get a ZeroDivisionError from the following code:

python
def div(x, y):
return x / y

div(1, 0)



### Do

I get a ZeroDivisionError from the following code:

python
def div(x, y):
return x / y

div(1, 0)


python-traceback
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-4-7b96263abbfa> in <module>()
----> 1 div(1, 0)

<ipython-input-3-7685f97b4ce5> in div(x, y)
1 def div(x, y):
----> 2     return x / y
3

ZeroDivisionError: division by zero



If the traceback is long that’s ok. If you really want to be clean you can put it in <details> brackets.

I get a ZeroDivisionError from the following code:

python
def div(x, y):
return x / y

div(1, 0)


### Traceback

<details>

python
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-4-7b96263abbfa> in <module>()
----> 1 div(1, 0)

<ipython-input-3-7685f97b4ce5> in div(x, y)
1 def div(x, y):
----> 2     return x / y
3

ZeroDivisionError: division by zero


</details>


### Ask Questions in Public Places

When raising issues you often have a few possible locations:

1. GitHub issue tracker
2. Stack Overflow
3. Project mailing list
4. Project Chat room
5. E-mail maintainers directly (never do this)

Different projects handle this differently, but they usually have a page on their documentation about where to go for help. This is often labeled “Community”, “Support” or “Where to ask for help”. Here are the recommendations from the Pandas community.

Generally it’s good to ask questions where many maintainers can see your question and help, and where other users can find your question and answer if they encounter a similar bug in the future.

While your goal may be to solve your problem, the maintainer’s goal is likely to create a record of how to solve problems like yours. This helps many more users who will have a similar problem in the future, see your well-crafted bug report, and learn from the resulting conversation.

### My personal preferences

• For user questions like “What is the right way to do X?” I prefer Stack Overflow.
• For bug reports like “I did X, I’m pretty confident that it should work, but I get this error” I prefer Github issues
• For general chit-chat I prefer Gitter, though actually, I personally spend almost no time in gitter because it isn’t easily searchable by future users. If you’ve asked me a question in Gitter I will almost certainly not respond to it, except to direct you to github, stack overflow, or this blogpost.
• I only like personal e-mail if someone is proposing to fund or seriously support the project in some way

But again, different projects do this differently and have different policies. You should check the documentation of the project you’re dealing with to learn how they like to support users.

## February 27, 2018

### Continuum Analytics

#### Introducing Microsoft R Open as Default R for Anaconda Distribution

Although Anaconda, Inc. is best known as the creator of the world’s most popular Python data science platform, for many years we also have been creating conda packages for R. In September 2017, we announced a partnership with Microsoft that included bringing Microsoft R Open (MRO) to Anaconda users as our default R. We are …