#21323 closed defect (wontfix)
Configure OpenBLAS to be single threaded
| Reported by: | cpernet | Owned by: | |
|---|---|---|---|
| Priority: | major | Milestone: | sage-duplicate/invalid/wontfix |
| Component: | linear algebra | Keywords: | BLAS, sd75 |
| Cc: | Merged in: | ||
| Authors: | Reviewers: | Jean-Pierre Flori, Clément Pernet | |
| Report Upstream: | N/A | Work issues: | |
| Branch: | Commit: | ||
| Dependencies: | Stopgaps: |
Description (last modified by )
OpenBLAS is currently configured to run in multithreaded mode. This prevents a user to have control over the number of threads of his sage computation (in case he wants to split it in several processes).
Instead, I suggest to configure it with the USE_THREAD=0 option which makes it a sequential BLAS.
Note that LinBox? parallel routines (not yet exposed in SageMath) required a sequential BLAS. In turn they offer parallel speed-up of the same order, but with the option to set the number of threads as a parameters to the function called.
Change History (9)
comment:1 Changed 3 years ago by
- Type changed from PLEASE CHANGE to defect
comment:2 Changed 3 years ago by
- Branch set to u/cpernet/configure_openblas_to_be_single_threaded
comment:3 Changed 3 years ago by
- Commit set to 8a863727c15b9c7e3bae02fc9cb07ef8f2ce5280
- Description modified (diff)
comment:4 Changed 3 years ago by
- Commit changed from 8a863727c15b9c7e3bae02fc9cb07ef8f2ce5280 to 85f25f68f6a8783a5c2f158009928b9d0fcec450
Branch pushed to git repo; I updated commit sha1. New commits:
| 85f25f6 | revert the order of arguments: so as to let user the opportunity to override it.
|
comment:5 Changed 3 years ago by
- Status changed from new to needs_review
comment:6 Changed 3 years ago by
- Reviewers set to Jean-Pierre Flori
- Status changed from needs_review to needs_info
I see in OpenBLAS doc (https://github.com/xianyi/OpenBLAS/wiki/faq):
How can I use OpenBLAS in multi-threaded applications? If your application is already multi-threaded, it will conflict with OpenBLAS multi-threading. Thus, you must set OpenBLAS to use single thread as following. * export OPENBLAS_NUM_THREADS=1 in the environment variables. Or * Call openblas_set_num_threads(1) in the application on runtime. Or * Build OpenBLAS single thread version, e.g. make USE_THREAD=0
So it seems we could disable mt at runtime. Any thought abour this?
comment:7 Changed 3 years ago by
- Branch u/cpernet/configure_openblas_to_be_single_threaded deleted
- Commit 85f25f68f6a8783a5c2f158009928b9d0fcec450 deleted
- Milestone changed from sage-7.4 to sage-duplicate/invalid/wontfix
- Reviewers changed from Jean-Pierre Flori to Jean-Pierre Flori, Clément Pernet
- Status changed from needs_info to positive_review
Right. After thinking this through, we figured that the best option is to have fflas-ffpack call the openblas_set_num_threads(1) before each call to OpenBLAS.
This ticket therefore becomes https://github.com/linbox-team/fflas-ffpack/issues/42
comment:8 Changed 3 years ago by
- Resolution set to wontfix
- Status changed from positive_review to closed
Determined to be invalid/duplicate/wontfix (closing as "wontfix" as a catch-all resolution).
comment:9 Changed 14 months ago by
See #26118 for a related issue.
New commits:
add USE_THREAD=0 argument to OpenBLAS configure