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OpenBLAS hangs with USE_OPENMP=1 #62

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xianyi opened this issue Oct 3, 2011 · 0 comments
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OpenBLAS hangs with USE_OPENMP=1 #62

xianyi opened this issue Oct 3, 2011 · 0 comments
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0.1.0 stable release

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xianyi commented Oct 3, 2011

The user Amarnath Balachandar reported a hang bug.

OpenBLAS is compiled with USE_OPENMP=1 and BINARY=64.

The multi-threaded appliction would hang with setting OPENBLAS_NUM_THREADS only. Instead, it would ok with setting OMP_NUM_THREADS.
@ghost ghost assigned xianyi Oct 3, 2011
xianyi added a commit that referenced this issue Oct 9, 2011
@xianyi
ref #62. Added the user friendly message with USE_OPENMP=1. The users…
57658a8 
… should use OMP_NUM_THREADS.

When OpenBLAS is compiled with USE_OPENMP=1, it ignores OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS flags.Therefore, you should use OMP_NUM_THREADS.

Without setting OMP_NUM_THREADS, a process will use maximal number of threads on a computing node. Thus, if there are 2 processes on the computing node, the thread will contend against other threads on CPU cores. As a result, the application will hang.
xianyi added a commit that referenced this issue Oct 16, 2011
@xianyi
Ref #62. In OpenMP implementation, check the return value of omp_get_…
ba31b19 
…max_threads().

It makes sure the return value as same as blas_cpu_numbers which is an internal global variable to store the number of threads in OpenBLAS.
@xianyi xianyi closed this as completed Oct 17, 2011
@svaksha svaksha mentioned this issue Apr 9, 2013
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martin-frbg added a commit that referenced this issue Jun 7, 2020
@martin-frbg
Merge pull request #62 from xianyi/develop
0f9a935 
rebase
kseniyazaytseva pushed a commit to kseniyazaytseva/OpenBLAS that referenced this issue Dec 19, 2023
@kseniyazaytseva
Pull request OpenMathLib#62: [LS-886][LS-914] Fix SegFaults and hangs…
64f673a 
… in LAPACK tests for RVV 0.7 targets

Merge in PL/openblas from dev/an.sokolov/fix_segfault to dev-riscv
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