MPI_ALLTOALL(sendbuf, sendcount, sendtype, recvbuf,
recvcount, recvtype, comm)
int MPI_Alltoall(void* sendbuf, int sendcount, MPI_Datatype sendtype, void* recvbuf, int recvcount, MPI_Datatype recvtype, MPI_Comm comm)
MPI_ALLTOALL(SENDBUF, SENDCOUNT, SENDTYPE, RECVBUF, RECVCOUNT, RECVTYPE, COMM, IERROR)
<type> SENDBUF(*), RECVBUF(*)
INTEGER SENDCOUNT, SENDTYPE, RECVCOUNT, RECVTYPE, COMM, IERROR
MPI_ALLTOALL is an extension of MPI_ALLGATHER to the case where each process sends distinct data to each of the receivers. The jth block sent from process i is received by process j and is placed in the ith block of recvbuf.
The type signature associated with sendcount, sendtype, at a process must be equal to the type signature associated with recvcount, recvtype at any other process. This implies that the amount of data sent must be equal to the amount of data received, pairwise between every pair of processes. As usual, however, the type maps may be different.
The outcome is as if each process executed a send to each
process (itself included)
with a call to,
All arguments on all processes are significant. The argument comm must have identical values on all processes.
MPI_ALLTOALLV(sendbuf, sendcounts, sdispls, sendtype,
recvbuf, recvcounts, rdispls, recvtype, comm)
int MPI_Alltoallv(void* sendbuf, int *sendcounts, int *sdispls, MPI_Datatype sendtype, void* recvbuf, int *recvcounts, int *rdispls, MPI_Datatype recvtype, MPI_Comm comm)
MPI_ALLTOALLV(SENDBUF, SENDCOUNTS, SDISPLS, SENDTYPE, RECVBUF, RECVCOUNTS, RDISPLS, RECVTYPE, COMM, IERROR)
<type> SENDBUF(*), RECVBUF(*)
INTEGER SENDCOUNTS(*), SDISPLS(*), SENDTYPE, RECVCOUNTS(*), RDISPLS(*), RECVTYPE, COMM, IERROR
MPI_ALLTOALLV adds flexibility to MPI_ALLTOALL in that the location of data for the send is specified by sdispls and the location of the placement of the data on the receive side is specified by rdispls.
The jth block sent from process i is received by process j and is placed in the ith block of recvbuf. These blocks need not all have the same size.
The type signature associated with sendcount[j], sendtype at process i must be equal to the type signature associated with recvcount[i], recvtype at process j. This implies that the amount of data sent must be equal to the amount of data received, pairwise between every pair of processes. Distinct type maps between sender and receiver are still allowed.
The outcome is as if each process sent a message to every other process
with,
All arguments on all processes are significant. The argument comm must have identical values on all processes.
MPI-Standard for MARMOT