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cpython 3.13 installed with UV slow and not compiled with --enable-experimental-jit=yes-off
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#535
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Thanks for the report. Do you know if Conda builds with any particular performance flags? |
I did an actual performance run (Linux x86-64) and it looks like there's a significant difference here
I consider this fairly high priority, but I don't know what the source of the difference is. |
Looking at https://github.com/conda-forge/python-feedstock/blob/main/recipe/build_base.sh and not seeing anything obvious. |
@paugier What platform and architecture did you run your benchmarks on? |
It looks like they might use -O3 instead of -O2 edit: This is already the default in CPython https://github.com/python/cpython/blob/94a7279fbdcfc2ccb6e7bb3c1cec863cce30a591/configure#L9600 |
Our v3 builds are a bit better, but that's not the bulk of it (geometric mean: 1.20x slower) |
FWIW, I don't see any slowdown on conda-forge 3.13 vs uv 3.14.0a5 on my machine (AMD64 Linux) on this benchmark:
In fact, the conda forge is significantly slower |
3.14 <-> 3.13 doesn't feel like a fair comparison since we're using the tail calling interpreter. |
Oh wow, I do see a significant slowdown on 3.13 (compare the previous comment)
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I tried a very simple pure Python benchmark (see https://gricad-gitlab.univ-grenoble-alpes.fr/augierpi/augierpi.gricad-pages.univ-grenoble-alpes.fr/-/tree/branch/default/content/docs/2025/about-py-jit) and figured out that CPython 3.13 installed with UV is slower than CPython 3.13 installed from conda-forge.
The benchmark is very simple (the goal was to be able to observe an effect of the new JIT in CPython 3.13):
The results:
This is bad:
--enable-experimental-jit=yes-off
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