On Sat, Nov 6, 2021 at 3:51 PM Mark Adams <[email protected]> wrote:

Yea, that is a bit inscrutable, but I see mumps is the main/only user of this:

/* if using PETSc OpenMP support, we only call MUMPS on master ranks. Before/after the call, we change/restore CPUs the master ranks can run on */

And I see _OPENMP is a macro for the release date (yyyymm) of the OMP version. It's not clear what the v5.0 is ( https://www.openmp.org/specifications/)

{200505,"2.5"},{200805,"3.0"},{201107,"3.1"},{201307,"4.0"},{201511,"4.5"},{201811,"5.0"},{202011,"5.1"} On Sat, Nov 6, 2021 at 4:27 PM Junchao Zhang <[email protected]>

wrote:

...

On Sat, Nov 6, 2021 at 5:51 AM Mark Adams <[email protected]> wrote:

...

Two questions on OMP:

* Can I test for the version of OMP? I want >= 5 and I see this, which looks promising: include/petscsys.h:#elif defined(_OPENMP) && *_OPENMP >= 201307* && !defined(_WIN32)

* What is the difference between HAVE_OPENMP and HAVE_OPENMP_SUPPORT.

# this is different from HAVE_OPENMP. HAVE_OPENMP_SUPPORT checks if we have facilities to support # running PETSc in flat-MPI mode and third party libraries in MPI+OpenMP hybrid mode if self.mpi.found and self.mpi.support_mpi3_shm and self.pthread.found and self.hwloc.found: # Apple pthread does not provide this functionality if self.function.check('pthread_barrier_init', libraries = 'pthread'): self.addDefine('HAVE_OPENMP_SUPPORT', 1)

...

Thanks, Mark