The Zen of Scientific computing¶
Have you ever felt like all your work was built as a house of cards, ready to crash down at any time?
Have you ever felt that you are far too inefficient to survive?
No, you’re not alone. Yes, there is a better way.
Production code vs research code¶
Yes, many things about software development may not apply to you:
you sort of know what the target is
code is the main result
must be maintainable for the future
you don’t know what the target is
code is secondary
But research code often becomes important in the future, so not all can be an unmaintainable mess…
Research code pyramid¶
I know that not all research code will be perfect.
But if you don’t build on a good base, you will end up with misery.
Yes, you can’t do everything perfectly¶
Not everything you do will be perfect. But it has to be good enough to:
be changed without too much difficulty
be run again once reviews come in
ideally, not wasted once you do something new
Even as a scientist, you need to know the levels of maturity so that you can do the right thing for your situation.
It takes skill and practice to do this right. But it is part of being a scientist.
This talk’s outline:
Describe different factors that influence code quality
Describe what the maturity levels are and when you might need them
What aspects can you improve?¶
Below are many different aspects of scientific computing which you can improve.
Some are good for everyone. Some you may not need yet. Different levels of maturity are presented for each topic, so that you can think about what is right for you.
Version control allows you to track changes and progress.
For example, you can figure out what you just broke or when you introduced a bug. You can always go back to other versions.
Version control is essential to any type of collaboration.
L0: no version control
L1: local repo, just commit for yourself
L2: shared repo, multiple collaborators push directly
L3: shared repo, pull-request workflow
Modularity is one of the basic prerequisites to be able to understand, maintain, and reuse things - and also hard to get right at the beginning.
Don’t worry too much, but always think about how to make things reusability.
L0: bunch of copy-and-paste scripts
L1: important code broken out into functions
L2: separation between well-maintained libraries and daily working scripts.
CodeRefinery Modular Code Development lesson
You will need to store many files. Are they organized, so that you can find them later, or will you get lost in your own mess?
L0: no particular organization system
L1: different types of data separated (original data/code/scratch/outputs)
L2: projects cleanly separated, named, and with a purpose
I don’t know of good sources for this.
But you can find different recommendations for organizational systems
When you are doing serious work, you can’t afford to just manage stuff by hand. Task automation allows you to do more faster.
Something such as
make can automatically detect changed input
files and code and automatically generate the outputs.
L0: bunch of scripts you have to run and check output of by hand.
L1: hand-written management scripts, each output can be traced to its particular input and code.
makeor other workflow management tool to automate things.
L3: Full automation from original data to final figures and data
CodeRefinery Reproducible Research lesson
Reproducibility of environment¶
Is someone else able to (know and) install the libraries needed to run your code? Will a change in another package break your code?
Scientific software is notoriously bad at managing its dependencies.
L0: no documentation
L1: state the dependencies somewhere, tested to ensure they work
L2: pin exact versions used to generate your results
L3: containerized workflow or equivalent
CodeRefinery Reproducible Research lesson
If you don’t say what you do, there’s no way to understand it. You won’t be able to understand it later, either.
At minimum, there should be some README files that explain the big picture. There are fancier systems, too.
L0: nothing except scattered code comments
L1: script-level comments and docstrings explaining overall logic
L2: simple README files explaining big picture and main points (example)
L3: dedicated documenentation including tutorials, reference, etc.
CodeRefinery Documentation lesson
You have to test your code at least once when you first run it. How do you know you don’t break something later?
Testing gives you a way to ensure things always work (and are correct) in the future by letting you run every test automatically.
There’s nothing more liberating than knowing “tests still pass, I didn’t break anything”. It’s extremely useful for debugging, too.
L0: ad-hoc and manually
L1: defensive programming (assertions), possibly some test data and scripts
L2: structured, comprehensive unit/integration/system tests (e.g.
L3: continuous integration testing on all commits (e.g. Github Actions)
If code is easy to test, it is usually easy to reuse, too. Furthermore, making code testable makes it reusable.
You presumably want people to use your work so they will cite you. If you don’t have a license, they won’t (or they might and not tell anyone).
Equally, you want to use other people’s work. You need to check their licenses.
L0: no license given / copy and paste from other sources
L1: license file in repo / careful to not copy incompatible code
L2: license tracked per-file and all contributors known.
Code can be easy to reuse, but not easy to get. Luckily there are good systems for sharing code.
L0: code not distributed
L1: code provided only if someone asks
L2: code on a website
L3: version control system repo is public
L4: packaged, tagged, and versioned releases
Python: Packaging tutorial
Similar for any other language you may use
Are you aware of what what others have already figured out through their great effort?
Choosing the right thing to build off of is not always easy, but you must
L0: reinvent everything yourself
L1: use some existing tools and libraries
L2: deep study of existing solutions and tools, reuse them when appropriate
I don’t know where to refer you to right now.
Is science like monks working in their cells, or a community effort?
These skills move so fast that learning peer-to-peer is one of the best ways to do it.
There’s a whole other art of applying these skills which isn’t taught in classes.
If you don’t work together, you will fall behind.
L0: you work alone and re-invent everything
L1: you occasionally talk about results or problems
L2: collaborative package development
L3: code reviews, pair programming, etc.
L4: community project welcoming other contributors
Most every CodeRefinery lesson
Science with computers can be extremely enjoyable… or miserable.
We are here to help you. You are here to others.