Add OPENBLAS_DEFAULT_NUM_THREADS
#3773
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This allows Julia to set a default number of threads (usually `1`) to be used when no other thread counts are specified [0], to short-circuit the default OpenBLAS thread initialization routine that spins up a different number of threads than Julia would otherwise choose. The reason to add a new environment variable is that we want to be able to configure OpenBLAS to avoid performing its initial memory allocation/thread startup, as that can consume significant amounts of memory, but we still want to be sensitive to legacy codebases that set things like `OMP_NUM_THREADS` or `GOTOBLAS_NUM_THREADS`. Creating a new environment variable that is openblas-specific and is not already publicly used to control the overall number of threads of programs like Julia seems to be the best way forward. [0] JuliaLang/julia#46844
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Sorry for the delay here - I guess it would be nicer if the existing OPENBLAS_NUM_THREADS could be reworked to act the same with both pthreads and OpenMP, but a way to limit the thread count for just this library rather than the entire process does certainly make sense in any case. |
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This was add to OpenBLAS in OpenMathLib/OpenBLAS#3773 and was supposed to be used in #46844 but was likely typod
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…#48064) This was add to OpenBLAS in OpenMathLib/OpenBLAS#3773 and was supposed to be used in #46844 but was likely typod
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…#48064) This was add to OpenBLAS in OpenMathLib/OpenBLAS#3773 and was supposed to be used in #46844 but was likely typod (cherry picked from commit 75bc5ee)
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…#48064) This was add to OpenBLAS in OpenMathLib/OpenBLAS#3773 and was supposed to be used in #46844 but was likely typod (cherry picked from commit 75bc5ee)
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This allows Julia to set a default number of threads (usually
1) to be used when no other thread counts are specified [0], to short-circuit the default OpenBLAS thread initialization routine that spins up a different number of threads than Julia would otherwise choose.The reason to add a new environment variable is that we want to be able to configure OpenBLAS to avoid performing its initial memory allocation/thread startup, as that can consume significant amounts of memory, but we still want to be sensitive to legacy codebases that set things like
OMP_NUM_THREADSorGOTOBLAS_NUM_THREADS. Creating a new environment variable that is openblas-specific and is not already publicly used to control the overall number of threads of programs like Julia seems to be the best way forward.[0] JuliaLang/julia#46844