I am trying to find the neighbor ranks in a 3D cartesian communicator. I
use MPI_Cart_shift for 6 of them, but for the 12 diagonals I tried to
use MPI_Cart_rank. However, only x-direction is periodic and my program
crashed because of out-of-range coordinates. Then I found something
strange in some MPICH documentation:
"Out-of-range coordinates are erroneous for non-periodic dimensions .
Versions of MPICH before 1.2.2 returned MPI_PROC_NULL for the rank in
Why doesn't it anymore? Is this the same for OpenMPI? I expected it to
return MPI_PROC_NULL which would make things much easier.