Global Communication

The ALL-to-ALL communication test :

C every processor sends message to every other processor

C then every processor receives messages directed to it.

T0 = mpi_time()

Do I = 1, NREPT

CALL mpi_alltoall (A, iw, MPI_DOUBLE_PRECISION,

B, iw, MPI_DOUBLE_PRECISION,

MPI_COMM_WORLD,ier)

End do

T1 = mpi_time()

Tn = (T1-T0)/(NREPT*NP*(NP-1)) ! NP processes send NP-1 messages

T0 = mpi_time()

Do I = 1, NREPT

CALL shmem_barrier_all ()

Do j=0, NP-1

other = MOD (my_rank+j, NP)

CALL shmem_put8(B(1+iw*my_rank), A(1+iw*other), iw, other)

enddo

T1 = mpi_time()

Tn = (T1-T0)/(NREPT*NP*(NP-1)) ! NP processes send NP-1 messages

MPI Version

SHMEM Version