MPI_Ialltoallw

Nonblocking generalized all-to-all communication allowing different datatypes, counts, and displacements for each partner

Synopsis

int MPI_Ialltoallw(const void *sendbuf, const int sendcounts[], const int sdispls[],
                   const MPI_Datatype sendtypes[], void *recvbuf, const int recvcounts[],
                   const int rdispls[], const MPI_Datatype recvtypes[], MPI_Comm comm,
                   MPI_Request * request)

Input Parameters

sendbuf
starting address of the send buffer (choice)
sendcounts
non-negative integer array (of length group size) specifying the number of elements to send to each processor
sdispls
integer array (of length group size). Entry j specifies the displacement relative to sendbuf from which to take the outgoing data destined for process j
sendtypes
array of datatypes (of length group size). Entry j specifies the type of data to send to process j (array of handles)
recvcounts
non-negative integer array (of length group size) specifying the number of elements that can be received from each processor
rdispls
integer array (of length group size). Entry i specifies the displacement relative to recvbuf at which to place the incoming data from process i
recvtypes
array of datatypes (of length group size). Entry i specifies the type of data received from process i (array of handles)
comm
communicator (handle)

Output Parameters

recvbuf
starting address of the receive buffer (choice)
request
communication request (handle)

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

Errors

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.