OpenMathLib / OpenMathLib/OpenBLAS
OpenBLAS becomes single-threaded
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Description
Hi everybody,
I am using standard lapack routines to diagonalize moderately large matrices with openBLAS.
The box is a xeon with 6 cores and hyperthreading. At runtime execution starts with 12 threads
by default and after some reproducible time goes down to one thread with miserable performance
but execution is without errors. I have observed the same behavior with OMP_NUM_THREADS=2,4,6
and using also OPENBLAS_NUM_THREADS. I tried to set OMP_DYNAMIC=FALSE with no change of behavior. It is a locally compiled version of openBLAS 0.3.3 with gcc/gfortran 7.3.0
any hints would be appreciated !
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Research direction
Start by reproducing the reported behavior with the standard LAPACK routines in the locally compiled OpenBLAS 0.3.3 build. Compare OMP_NUM_THREADS, OPENBLAS_NUM_THREADS, and OMP_DYNAMIC settings while monitoring the transition from multiple threads to one. Done means identifying why the thread count drops and documenting or fixing the cause.
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Assessment
- Tech stack
- c, fortran
- Domain
- performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100