Vector variants

Vector Variants

• The gather, scatter, allgather, and alltoall routines all have vector variants in which the each process can send and/or receive a different number of elements.
• For example, the simple version of gather routine:

  mpi_gather (sendbuf, sendcount, sendtype,
              recvbuf, recvcount, recvtype,
              root, comm, ierr)

• The vector version is:

  mpi_gatherv (sendbuf,sendcount,sendtype,
               recvbuf, recvcounts, displs,
               recvtype, root, comm, ierr)

• recvcounts is an array giving number of elements received from each process
• displs is an array giving displacement at which to store the elements received from each process.