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MPI_Alltoallv - Sends data from all to all processes, with a displacement
#include <mpi.h>
int MPI_Alltoallv(void *sbuf, int *scounts, int *sdisps,
MPI_Datatype sdtype, void *rbuf, int *rcounts,
int *rdisps, MPI_Datatype rdtype,
MPI_Comm comm)
sbuf
- starting address of send buffer (choice)
scounts
- integer array equal to the group size specifying the number of elements to send to each processor
sdisps
- 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
sdtype
- data type of send buffer elements (handle)
rcounts
- integer array equal to the group size specifying the maximum number of elements that can be received from each processor
rdisps
- integer array (of length group size). Entry i specifies the displacement (relative to recvbuf at which to place the
incoming data from process i
rdtype
- data type of receive buffer elements (handle)
comm
- communicator (handle)
rbuf
- address of receive buffer (choice)
The receive buffer rbuf needs to be large enough to hold the data that will be received from all processes.
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.
If an error occurs in an MPI function, the current MPI error handler is called to handle it. By default, this error handler
aborts the MPI job. The error handler may be changed with MPI_Errhandler_set; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned (in C and Fortran; this error handler is less useful in with the C++ MPI
bindings. The predefined error handler MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value needs to be
recovered). Note that MPI does not guarantee that an MPI program can continue past an error.
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. The C++ bindings
for MPI do not return error values; instead, error values are communicated by throwing exceptions of type MPI::Exception
(but not by default). Exceptions are only thrown if the error value is not MPI::SUCCESS.
Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return upon an error, there will be
no way to recover what the actual error value was.
MPI_ERR_COMM
- Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank).
MPI_ERR_COUNT
- Invalid count argument. Count arguments must be non-negative; a count of zero is often valid.
MPI_ERR_TYPE
- Invalid datatype argument. May be an uncommitted MPI_Datatype (see MPI_Type_commit).
MPI_ERR_BUFFER
- Invalid buffer pointer. Usually a null buffer where one is not valid.
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