Waits for some given communications to complete


#include "mpi.h"
int MPI_Waitsome( incount, array_of_requests, outcount, array_of_indices, 
    array_of_statuses )
int         incount, *outcount, array_of_indices[];
MPI_Request array_of_requests[];
MPI_Status  array_of_statuses[];

Input Parameters

incount - length of array_of_requests (integer)
array_of_requests - array of requests (array of handles)

Output Parameters

outcount - number of completed requests (integer)
array_of_indices - array of indices of operations that completed (array of integers)
array_of_statuses - array of status objects for operations that completed (array of Status)


The array of indicies are in the range 0 to incount - 1 for C and in the range 1 to incount for Fortran.

Null requests are ignored; if all requests are null, then the routine returns with outcount set to MPI_UNDEFINED.

Note on status for send operations

For send operations, the only use of status is for MPI_Test_cancelled or in the case that there is an error, in which case the MPI_ERROR field of status will be set.

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.


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_Errhandler_set; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error.

MPI_SUCCESS - No error; MPI routine completed successfully.
MPI_ERR_REQUEST - Invalid MPI_Request. Either null or, in the case of a MPI_Start or MPI_Startall, not a persistent request.
MPI_ERR_ARG - Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).