Current version of openblas is not multi-threaded due to a bug in an ebuild file, where "USE_THREAD=0 USE_OPENMP=1" are set both during the configuration phase. If threads are disabled the openmp will not be used as it necessary requires pthread library. Reproducible: Always Steps to Reproduce: 1. compile openblas with openmp flag enabled 2. ldd /usr/lib64/libopenblas_openmp.so -> it is not linked against libgomp.so Actual Results: Using e.g. Octave for heavy computations it can be perceived that multi-threading is not in use. Expected Results: Parallel version of openblas compiled correctly. I have modified the ebuild (see the attachment) to set only USE_OPENMP=1 if openmp flag is enabled. Furthemore, the flag "threads" was removed since it says whether threads should be used or not (USE_OPENMP=1 -> USE_THREADS=1 and vice versa). Please correct me if I am wrong.
Created attachment 389130 [details] emerge --info
Created attachment 389132 [details] Modified ebuild file which solves the openmp issue. I will be grateful for any remarks regarding ebuild modification.
Well it now breaks the build: make -j12 -j1 libs shared INTERFACE64=1 USE_THREAD=0 USE_OPENMP=1 LIBNAMESUFFIX=int64_openmp Makefile.system:370: *** OpenBLAS: Cannot set both USE_OPENMP=1 and USE_THREAD=0. The USE_THREAD=0 is only for building single thread version.. Stop. Historically you had to use either USE_OPENMP or USE_THREAD but not both at the same time, the meaning of those must have changed.
+ 02 Apr 2015; Marius Brehler <marbre@linux.sungazer.de> openblas-9999.ebuild: + Fix Bug 528974 + Version 0.2.12 and 0.2.14 are symlinks that point to 9999. Should be fixed.
