windows crashed with error:Program will terminate because you tried to start too many threads

[yplypl]

i build openblas with following actions:

1. Install CMake at Windows
2. cmake -G "Visual Studio 12 Win64" -DCMAKE_BUILD_TYPE=Release .
   3: open vs2013 and build success.

i am not familiar with the build process, can any one tell me how to build to cross this limit.
by the way, crash is not that acceptable for me.

[brada4]

And what code leads to errors?
Do you run result on same machine as build?
Which OpenBLAS version?

[martin-frbg]

Which version is this ? There was a bug in 0.3.1 that could cause this, but the problem is supposed to be fixed in 0.3.2 (or current develop)

[yplypl]

i just tried the last version V0.3.3 still the same error。
@brada4 yes， dll is called on the same build machine。
it crashed at blas_memory_alloc called by cblas_dgemm, call stack as below：

what‘s more， it don't crash at the first call, after several times called，this crash happed.

[yplypl]

my pc is win10 i5 4cores. may openblas_config.h can supply more help
openblas_config.h.txt

[martin-frbg]

The only strangeness in your openblas_config.txt is that the cpu support is identified as "generic" rather than Haswell, as if it did not identify the hardware correctly (although it did see four cpus). How many threads are you expecting to run in this context ? You may need to build with a higher number of NUM_THREADS to get around the problem if you are planning on more than 8 (4 + hyperthreading). (And there is still the possibility that some assumption in rewrite of the thread memory allocation code from 0.3.1 is incorrect, so you could also try if v0.3.0 shows similar problems)

[yplypl]

i just use one thread to call cblas_dgemm in one business loop。 and it crashed after 3 business loop finished。 if NUM_THREADS is not enough， it should crash in my first loop。
i hope one cblas_dgemm call， 4 below threads help to calculate will be great， but the calling thread num can be unlimited.

[martin-frbg]

Not sure how you are calling OpenBLAS, somehow this looks as if you are creating a new instance with every call (and the "old" ones still stay around). Does your code use OpenMP ?

[martin-frbg]

BTW this is related to #1641.

[yplypl]

yes，OpenMP is called at other place in my code。

[martin-frbg]

Did you build OpenBLAS with OpenMP support as well (USE_OPENMP=1) ?

[brada4]

As a side note - cuBLAS supports gemm that does not do host-device moves....

[yplypl]

could u tell me how to enable USE_OPENMP and change NUM_THREADS。
is following steps right？
1：Install CMake at Windows
2：cmake -G "Visual Studio 12 Win64" -DCMAKE_BUILD_TYPE=Release -DUSE_OPENMP=1 -DNUM_THREADS=20 .
3: open vs2013 and build success.

[martin-frbg]

Yes this should work.

[yplypl]

@brada4 yes, cuBlas is also used in my program, it works great。now i am trying to improve the cpu calculation performance。

[yplypl]

@martin-frbg
change to USE_OPENMP=1 -DNUM_THREADS=20 still the same error。but take a longer time to crash