MPI_Waitany(3)

NAME
MPI_Waitany - Waits for any specified send or receive to complete

SYNOPSIS
#include <mpi.h>
int MPI_Waitany(int count, MPI_Request *reqs, int *index,
  MPI_Status *stat)

INPUT PARAMETERS
count
    - list length (integer)
reqs
    - array of requests (array of handles)

OUTPUT PARAMETERS
index
    - index of handle for operation that completed (integer). In the range 0 to count-1
     . In Fortran, the range is 1 to count
     .
stat
    - status object (Status), or the MPI constant MPI_STATUS_IGNORE

NOTES
If all of the requests are MPI_REQUEST_NULL , then index is returned as MPI_UNDEFINED , and stat is returned as an empty status.

NOTE ON STATUS FOR SEND OPERATIONS
For send operations, the only use of status is for MPI_Test_cancelled 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.

ERRORS
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_SUCCESS
    - No error; MPI routine completed successfully.
MPI_ERR_REQUEST
    - Invalid MPI_Request ; either null or, MPI_REQUEST_NULL , in the case of a MPI_Start or MPI_Startall , not a persistent request.
MPI_ERR_COUNT
    - Invalid count argument. Count arguments must be non-negative; a count of zero is often valid.
MPI_ERR_ARG
    - Invalid argument. Some argument is invalid and is not identified by a specific error class. This is typically a NULL pointer or other such error.

MORE INFORMATION
For more information, please see the official MPI Forum web site, which contains the text of both the MPI-1 and MPI-2 standards. These documents contain detailed information about each MPI function (most of which is not duplicated in these man pages). http://www.mpi-forum.org/

ACKNOWLEDGEMENTS
The LAM Team would like the thank the MPICH Team for the handy program to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the initial formatting, and some initial text for most of the MPI-1 man pages.

LOCATION
waitany.c