User visible communicators generally do not have a keyval attached. Rather the keyval is attached to the inner communicator; because we don't want both PETSc and the user doing MPI operations on the same communicator (to prevent mixing up tags). I think PetscShmCommGet() is wrong. I think it should not call MPI_Comm_get_attr(globcomm,Petsc_Counter_keyval,&counter,&flg); but should call PetscCommDuplicate() and use that communicator to stash the pshmcomm; then you would not have the problem you are having. Barry

On Aug 12, 2021, at 11:05 AM, Pierre Jolivet <[email protected]> wrote:

Hello, Is there a specific reason why PETSC_COMM_WORLD is not a PETSc communicator, i.e., has no Petsc_Counter_keyval attached? ierr = PetscOmpCtrlCreate(PETSC_COMM_WORLD,nthreads,&ctrl);CHKERRQ(ierr); yields [0]PETSC ERROR: Bad MPI communicator supplied must be a PETSc communicator [0]PETSC ERROR: #1 PetscShmCommGet() at src/sys/utils/mpishm.c:60 [0]PETSC ERROR: #2 PetscOmpCtrlCreate() at src/sys/utils/mpishm.c:340

Thanks, Pierre