Without this flag, the configure script prints a warning at the end,
like this (reformatted):
If you want a release build with all stable optimizations active
(PGO, etc), please run ./configure --enable-optimizations
We're doing a build to distribute to people for day-to-day use,
doing things other than developing the Python interpreter. So
that's certainly a release build -- we're the target audience for
this recommendation.
---
And, trying it out, upstream isn't kidding! I ran the standard
benchmark suite that the CPython developers use for performance
work, "pyperformance". Following its usage instructions:
https://pyperformance.readthedocs.io/usage.html
I ran the whole suite, like so:
$ nix-shell -p ./result."$variant" --run '
cd $(mktemp -d); python -m venv venv; . venv/bin/activate
pip install pyperformance
pyperformance run -o ~/tmp/result.'"$variant"'.json
'
and then examined the results with commands like:
$ python -m pyperf compare_to --table -G \
~/tmp/result.{$before,$after}.json
Across all the benchmarks in the suite, the median speedup was 16%.
(Meaning 1.16x faster; 14% less time).
The middle half of them ranged from a 13% to a 22% speedup.
Each of the 60 benchmarks in the suite got faster, by speedups
ranging from 3% to 53%.
---
One reason this isn't just the default to begin with is that, until
recently, it made the build a lot slower. What it does is turn on
profile-guided optimization, which means first build for profiling,
then run some task to get a profile, then build again using the
profile. And, short of further customization, the task it would use
would be nearly the full test suite, which includes a lot of
expensive and slow tests, and can easily take half an hour to run.
Happily, in 2019 an upstream developer did the work to carefully
select a more appropriate set of tests to use for the profile:
https://github.com/python/cpython/commit/4e16a4a31https://bugs.python.org/issue36044
This suite takes just 2 minutes to run. And the resulting final
build is actually slightly faster than with the much longer suite,
at least as measured by those standard "pyperformance" benchmarks.
That work went into the 3.8 release, but the same list works great
if used on older releases too.
So, start passing that --enable-optimizations flag; and backport
that good-for-PGO set of tests, so that we use it on all releases.
The ./configure script prints a warning when passed this flag,
starting with 3.7:
configure: WARNING: unrecognized options: --with-threads
The reason is that there's no longer such a thing as a build
without threads.
Eliminate the warning, by only passing the flag on the older releases
that accept it.
Upstream change and discussion:
https://github.com/python/cpython/commit/a6a4dc816https://bugs.python.org/issue31370
- Replaced python override from the final stdenv, instead we
propagate our bootstrap python to stage4 and override both
CF and xnu to use it.
- Removed CF argument from python interpreters, this is redundant
since it's not overidden anymore.
- Inherit CF from stage4, making it the same as the stdenv.
This will turn manylinux support back on by default.
PIP will now do runtime checks against the compatible glibc version to
determine if the current interpreter is compatible with a given
manylinux specification. However it will not check if any of the
required libraries are present.
The motivation here is that we want to support building python packages
with wheels that require manylinux support. There is no real change for
users of source builds as they are still buildings packages from source.
The real noticeable(?) change is that impure usages (e.g. running `pip
install package`) will install manylinux packages that previously
refused to install.
Previously we did claim that we were not compatible with manylinux and
thus they wouldn't be installed at all.
Now impure users will have basically the same situation as before: If
you require some wheel only package it didn't work before and will not
properly work now. Now the program will fail during runtime vs during
installation time.
I think it is a reasonable trade-off since it allows us to install
manylinux packages with nix expressions and enables tools like
poetry2nix.
This should be a net win for users as it allows wheels, that we
previously couldn't really support, to be used.
It's a year until the final release but this will give a chance to test
out certain features and how it integrates with other packages.
https://www.python.org/dev/peps/pep-0596/
Python 3.8 fails to build on macOS for two reasons:
* python-3.x-distutils-C++.patch fails to apply cleanly.
* An #include for <util.h> is missing, causing a build failure:
./Modules/posixmodule.c:6586:9: error: implicit declaration of function 'openpty' is invalid in C99
if (openpty(&master_fd, &slave_fd, NULL, NULL, NULL) != 0)
^
Use the correct version of python-3.x-distutils-C++.patch, and add a
patch to #include <util.h>.
We don’t want cpython picking up /Library/Frameworks and
/System/Library/Frameworks which contains Tcl.framework. Instead it
should use the one provided by Nix. this would not be an issue if
sandboxing was enabled, but unfortunately that has its own issues.
Fixes#66647
There ver very many conflicts, basically all due to
name -> pname+version. Fortunately, almost everything was auto-resolved
by kdiff3, and for now I just fixed up a couple evaluation problems,
as verified by the tarball job. There might be some fallback to these
conflicts, but I believe it should be minimal.
Hydra nixpkgs: ?compare=1538299
Turns out fixing this only in importlib is not sufficient and we
need to backport CPython part of the fix too.
This patch is based on https://hg.python.org/cpython/rev/c16063765d3a
but because the code around is different there are some changes (C-strings
instead of Python objects etc.)
With this patch Tensorflow builds successfully on many-core machine.
This commit adds a Nix-specific module that recursively adds paths that
are on `NIX_PYTHONPATH` to `sys.path`. In order to process possible
`.pth` files `site.addsitedir` is used.
The paths listed in `PYTHONPATH` are added to `sys.path` afterwards, but
they will be added before the entries we add here and thus take
precedence.
The reason for adding support for this environment variable is that we
can set it in a wrapper without breaking support for `PYTHONPATH`.
This is python bug https://bugs.python.org/issue13146. Fixed since
python 3.4. It makes pyc creation atomic, preventing a race condition.
The patch has been rebased on our deterministic build patch.
It wasn't backported to python 2.7 because there was a complaint about
changed semantics. Since files are now created in a temporary directory
and then moved, symlinks will be overridden. See
https://bugs.python.org/issue17222.
That is an edge-case however. Ubuntu and debian have backported the fix
in 2013 already, making it mainstream enough for us to adopt.
Patching numpy.distutils used to be required for pythonPackages.cython
to build on darwin. It was later accidentally disabled during one of the
refactorings, but that did not break cython. This change reinstantiates
the patch. It still applies, so it should be low maintenance and it can
still be useful.
Originally introduced in 8970a9c and 1531b5e, these patches were lost in
efbe87f when the CPython version files were merged, likely due to
CPython 3.7 not needing them anymore. These patches should remain
in-tree until CPython 3.5 and 3.6 support is dropped completely.
Found with the diffoscope ( https://diffoscope.org/ ).
The upstream patch for distutils does not apply cleanly to Python
3.7.3's sources. (The patch applies cleanly to Python 3.7.2's sources,
but nixpkgs commit 0ddae82e6a6388466a825000139f9fb986b50418 upgraded
Python to 3.7.3.) Fix the patch to make python37 build on macOS.
This changeset allows for cross-compilation of Python packages. Packages
built with buildPythonPackage are not allowed to refer to the build
machine. Executables that have shebangs will refer to the host.
Each time a new major/minor version of CPython was released, a new
expression would be written, typically copied from the previous release.
Often fixes are only made in the current/latest release. By merging the
expressions it's more likely that modifications end up in all versions,
as is likely intended.
This commit introduces one expression for Python 3, and another for 2.7.
These two may also be merged, but it will result in a lot of extra
conditionals making the expression harder to follow.
A common passthru is introduced for CPython and PyPy.
python 2.7: use common passthru
