Yes, this is the behavior defined by the MPI standard. More precisely,
section 8.1.2 of the MPI 3.1 standard clearly states that the predefined
attributes only exists for MPI_COMM_WORLD.
George.
On Sun, Jul 8, 2018 at 1:55 AM Weiqun Zhang <weiqunzh...@lbl.gov> wrote:
> Hi,
>
> It appears that MPI_Comm_get_attr fails to get MPI_TAG_UB for
> sub-communicators created by MPI_Comm_split. I have tested the following
> programs with openmpi 3.1.1 and openmpi 1.10.2. MPI_Comm_get_attr works on
> MPI_COMM_WORLD, but not on sub-communicators. Is this expected?
>
> #include <stdio.h>
> #include <mpi.h>
>
> int main(int argc, char** argv)
> {
> MPI_Init(&argc, &argv);
>
> int rank;
> MPI_Comm_rank(MPI_COMM_WORLD, &rank);
> void* p; int flag;
> MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_TAG_UB, &p, &flag);
> if (!flag) {
> printf("MPI_COMM_WORLD: rank %d failed to get MPI_TAG_UB\n", rank);
> } else {
> printf("MPI_COMM_WORLD: rank %d succeeded to get MPI_TAG_UB\n",
> rank);
> }
>
> int color = rank%2;
> MPI_Comm comm;
> MPI_Comm_split(MPI_COMM_WORLD, color, rank, &comm);
> int rank2;
> MPI_Comm_rank(comm, &rank2);
> MPI_Comm_get_attr(comm, MPI_TAG_UB, &p, &flag);
> if (!flag) {
> printf("Subcommunicator %d rank %d failed to get MPI_TAG_UB\n",
> color, rank2);
> } else {
> printf("Subcommunicator %d rank %d succeeded to get MPI_TAG_UB\n",
> color, rank2);
> }
>
> MPI_Finalize();
> }
>
> program main
>
> use mpi
> implicit none
>
> integer :: ierr, rank, color, comm, rank2
> integer(kind=MPI_ADDRESS_KIND) :: attrval
> logical :: flag
>
> call MPI_Init(ierr)
>
> call MPI_Comm_rank(MPI_COMM_WORLD, rank, ierr)
> call MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_TAG_UB, attrval, flag, ierr)
> if (.not.flag) then
> print *, "MPI_COMM_WORLD: rank ", rank, " failed to get MPI_TAG_UB."
> else
> print *, "MPI_COMM_WORLD: rank ", rank, " succeeded to get
> MPI_TAG_UB."
> end if
>
> color = modulo(rank,2)
> call MPI_Comm_split(MPI_COMM_WORLD, color, rank, comm, ierr)
> call MPI_Comm_rank(comm, rank2, ierr)
> call MPI_Comm_get_attr(comm, MPI_TAG_UB, attrval, flag, ierr)
> if (.not.flag) then
> print *, "Subcommunicator ", color, " rank ", rank2, " failed to get
> MPI_TAG_UB."
> else
> print *, "Subcommunicator ", color, " rank ", rank2, " succeeded to
> get MPI_TAG_UB."
> end if
>
> call MPI_Finalize(ierr)
>
> end program main
>
> Thanks,
>
> Weiqun
>
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