We set the displacements for each block as the location of the first
element in the block. This works because MPI_Scatterv uses the extents
to determine the start of each piece to send.
scdispls = 0; scdispls = 4; scdispls = 32; scdispls = 36; MPI_Scatterv( sendbuf, sendcounts, scdispls, block, recvbuf, nx * ny, MPI_DOUBLE, 0, MPI_COMM_WORLD );127 How would use use the topology routines to make this more general?