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[MRG] DOC More details about parallelism (joblib, openMP, MKL...) #15116

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Merged
merged 13 commits into from
Oct 15, 2019
Merged

[MRG] DOC More details about parallelism (joblib, openMP, MKL...) #15116

merged 13 commits into from
Oct 15, 2019

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NicolasHug
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Follow up on #14265

ping @ogrisel @jeremiedbb please make sure I didn't write any nonsense :)

albertcthomas
albertcthomas reviewed Oct 2, 2019
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I cannot really assess the correctness but I find it very clear. I also like the small example with the 4 * 4 threads in total. Thanks!

rth
rth reviewed Oct 2, 2019
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Thanks @NicolasHug ! A few comments

@NicolasHug NicolasHug changed the title [MRG] DOC for controlling number of OpenMP threads [MRG] DOC More details about parallelism (joblib, openMP, MKL...) Oct 2, 2019
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I made a big update.

Tried to trim down the n_jobs glossary description and added more details in the UG.

That's pretty much all I know about this... Hope that's useful, feedback welcome

jeremiedbb
jeremiedbb reviewed Oct 3, 2019
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Look good overall. I find it very clear, thanks !

Numpy recently added the possibility to link against BLIS (another multi-threaded BLAS implementation). For completeness you could add BLIS everywhere you mention MKL and OpenBLAS :)
It also has a env var: BLIS_NUM_THREADS.

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Thanks a lot for the comments. @jeremiedbb joblib doesn't protect from oversubscription from BLIS for now, right?

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jeremiedbb commented Oct 3, 2019 •
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joblib doesn't protect from oversubscription from BLIS for now, right?

Actually it does because BLIS looks for OMP_NUM_THREADS as well.

(That might change in the future:
Note: We highly discourage use of the OMP_NUM_THREADS environment variable and may remove support for it in the future. If you wish to set parallelism globally via environment variables, please use BLIS_NUM_THREADS.)

jeremiedbb
jeremiedbb approved these changes Oct 3, 2019
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LGTM !

tomMoral
tomMoral reviewed Oct 3, 2019
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This is very clear and synthetic! Thanks @NicolasHug for doing this.
2/3 comments on some specific points.

tomMoral
tomMoral reviewed Oct 3, 2019
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@NicolasHug NicolasHug mentioned this pull request Oct 7, 2019
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ogrisel
ogrisel approved these changes Oct 7, 2019
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Overall, LGTM. Just a few improvement suggestions:

@ogrisel ogrisel merged commit 60ce68c into scikit-learn:master Oct 15, 2019
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ogrisel commented Oct 15, 2019

Merged! Thanks @NicolasHug.

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This might need an update depending on the outcome of #14196

@NicolasHug NicolasHug mentioned this pull request Jan 9, 2020
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@NicolasHug NicolasHug mentioned this pull request Jan 24, 2020
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@cmarmo cmarmo mentioned this pull request Mar 31, 2021
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@ogrisel ogrisel ogrisel approved these changes

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@NicolasHug @jeremiedbb @ogrisel @rth @tomMoral @thomasjpfan @albertcthomas