[SciPy-Dev] proposal to use SciPy project funds for build and CI improvements

Ralf Gommers ralf.gommers at gmail.com
Sun Jul 4 17:46:25 EDT 2021

Hi all,

I'd like to make a proposal to use some project funds to make faster
progress on moving to a new build system and improving our CI timeout

Because this is the first such proposal, let me first deal with the meta
issue of _how_ to deal with this. At the start of the year I co-wrote NEP
48 (https://numpy.org/neps/nep-0048-spending-project-funds.html) to have a
framework for NumPy for spending project funds. I'd like to follow that NEP
also for SciPy. So I'll make the proposal here, in accordance with that
NEP, and then the other thing is to figure out where to put it up as a PR
(or wiki page, or ...). For that my proposal is: create a new repo called
something like `project-mgmt`, where we can put such proposals as well as
meeting minutes, presentations, and other content. And have a single
summary page in Markdown format with a list of all proposals made, linking
out to the full proposals.

On to the actual proposal, keeping in mind

Title: Accelerating the move to Meson as the SciPy build system
Cost: $12,000
Time duration: 3 months
Team members: Matthew Brett (funded), Ralf Gommers (unfunded), Gagandeep
Singh (unfunded), Smit Lunagariya (funded)


   1. Multiple people recently told me that our current build system and CI
   issues are a pain point for working on SciPy. We have CI timeouts on our
   main repo, scipy-wheels is a pain, conda-forge is also timing out on
   aarch64 and ppc64le build. And I've found myself spending a whole day or
   weekend several times in the past months to fix broken CI jobs due to
   build/packaging issues.
   2. About 4 months ago, I wrote an RFC to move to Meson as a build
   system, see https://github.com/scipy/scipy/issues/13615. Since then I
   have spent a lot of time on this, and also used Quansight Labs funding to
   get one of my colleagues, Gagandeep Singh, to help me move this forward
   faster (and he has been super helpful). Getting a Linux + OpenBLAS dev
   build is close to done (16 of 20 modules complete, all that's left is
   `misc`, `io`, `integrate` and `signal` - probably those can be completed in
   the coming week).
   3. Doing everything else, like adding support for
   Windows/aarch64/MKL/ILP64/etc. is still a lot of work. There's a tracking
   issue at https://github.com/rgommers/scipy/issues/22. Some of this stuff
   is pretty specialized, e.g., building wheels, and Fortran-on-Windows. It
   will take a long time to complete if it's just me spending time on the
   4. Matthew Brett is available to help soon. He has written multibuild
   and dealt with build/packaging topics for a long time, so I think he would
   be able to make progress quickly. He wants to work on this topic as an
   independent contractor (I won't add rates here, that's for the core team to
   look at - but they're very reasonable).

The overall goals of this effort are:

   1. Get a (mostly) feature-complete Meson based build system in place by
   the end of October, so we can ship it in the 1.8.0 release. If all goes
   well, get rid of the `numpy.distutils` based build 1 release later.
   2. Resolve all our CI timeout issues. If the build system alone isn't
   enough (it should be though), analyze the remaining issues and figure out
   how to tackle whatever is still problematic.

The deliverables are, in order of priority:

   1. Add capability to build release artifacts (wheels, sdist). I did some
   initial tests at the start with mesonpep517, but I have no idea if it works
   for SciPy and what bugs are lurking there.
   2. macOS support
   3. Add support for things we need to a dev.py interface (basically, like
   runtests.py in that it can do everything, like building docs, running
   benchmarks, etc.)
   4. Contribute a few things we need, or that would make the build setup
   better, to Meson. For example, I think we'd want to be able to use
   `py3.install_sources` on generated targets. Of course I'm still new-ish to
   Meson, so it could well be that after making a proposal on the Meson issue
   tracker, another solution will be preferred.
   5. Windows support
   6. Improve build dependency detection and configuration - in particular
   BLAS/LAPACK flavors.
   7. Clean up as many build warnings as possible, and silence the rest.
   The goal is to have a CI job that is completely silent (passes with
   8. Optimize build time further, including on CI (e.g., reuse build cache
   between jobs).

I'd like to use 75% of the funds to pay Matthew, and 25% of the funds to
take on a talented intern, Smit Lunagariya. He is comfortable working in
Python, C and C++, and will be able to help with deliverables 7 and 8, as
well as with testing and other tasks.

Overall I'm not certain that this amount of funds is enough to complete
every last deliverable on this list; it's hard to estimate. But we should
certainly get close, and be able to ship a Meson build in 1.8.0.

For a quick sketch of the benefits:

   - On my machine the build time is currently 13 minutes with
   numpy.distutils and 90 seconds with Meson
   - The build log goes from >10,000 lines (mostly noise) to ~100 lines
   (mostly configuration info).

Why should this be a funded activity? For two reasons: (1) build and CI
issues are probably the number one maintenance issue we have, and (2) most
people find working on build/CI boring and painful, and hence it doesn't
happen with volunteer-only activities. Even regular maintenance of our CI
is hard - recently jobs have been broken for 1-2 weeks at a time a couple
of times. And the scipy-wheels repo is in even worse shape.

My proposal is to designate this topic as high priority, let the core team
approve the compensation levels for the funded people, and get the work
started. For reporting on progress and to have some accountability about
how we spent the funds, I propose a short report (say 1 page, giving a
status update and linking the main PRs made or issues closed) when half the
funds are spent, and another such report at the end.

In addition I'll plan to write a small development grant for this when the
next call for that opens up, because I think we want Matthew to continue
working on this after this $12,000 has been spent. I'd like to get
everything as good as it can be, so other projects can easily adopt Meson
as well - to also achieve my not-so-secret goal of not having to integrate
numpy.distutils capabilities into setuptools once distutils is removed from


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.python.org/pipermail/scipy-dev/attachments/20210704/9545491a/attachment.html>

More information about the SciPy-Dev mailing list