Mixing OpenMP with other threading paradigms

[gkaf89]

Regarding the compilation options, does it make sense to enable both USE_OPENMP and USE_THREAD?

In the file driver/others/memory.c I noticed that the use of some threading related code is always deactivated when OpenMP is used. For instance the directive

#if (defined(SMP) || defined(USE_LOCKING)) && !defined(USE_OPENMP)
...
#endif

is often used. Will this cause any issues?

[martin-frbg]

Yes this can/should both be enabled and USE_THREAD is on by default when you have more than one core in the build system. On many/most platforms, OpenMP is implemented on top of pthreads anyway.
Only use USE_THREAD=0 (on its own) when you want an OpenBLAS that does not use any form of multithreading at all (which can make sense if you have a big multithreaded program that makes many parallel calls to BLAS functions).
The directive you quoted is basically "if we are using multithreading, or expect to be called by multiple threads from outside, and we do not have OpenMP manage the locking for thread-safe concurrent accesses"