osx man page for mpi_get_count

MPI_Get_count(3OpenMPI) 												   MPI_Get_count(3OpenMPI)

NAME
       MPI_Get_count  - Gets the number of top-level elements received.

SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Get_count(MPI_Status *status, MPI_Datatype datatype,
	    int *count)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_GET_COUNT(STATUS, DATATYPE, COUNT, IERROR)
	    INTEGER   STATUS(MPI_STATUS_SIZE), DATATYPE, COUNT, IERROR

C++ Syntax
       #include <mpi.h>
       int Status::Get_count(const Datatype& datatype) const

INPUT PARAMETERS
       status	 Return status of receive operation (status).

       datatype  Datatype of each receive buffer element (handle).

OUTPUT PARAMETERS
       count	 Number of received elements (integer).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION
       Returns	the number of entries received. (We count entries, each of type datatype, not bytes.) The datatype argument should match the argu-
       ment provided by the receive call that set the status variable. (As explained in Section 3.12.5 in the  MPI-1  Standard,  "Use  of  General
       Datatypes in Communication," MPI_Get_count may, in certain situations, return the value MPI_UNDEFINED.)

       The  datatype  argument	is passed to MPI_Get_count to improve performance. A message might be received without counting the number of ele-
       ments it contains, and the count value is often not needed. Also, this allows the same function to be used after a call to MPI_Probe.

NOTES
       If the size of the datatype is zero, this routine will return a count of zero.  If the amount of data in status is not an exact multiple of
       the size of datatype (so that count would not be integral), a count of MPI_UNDEFINED is returned instead.

ERRORS
       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception  mechanism
       will be used to throw an MPI:Exception object.

       Before  the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for
       I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.

SEE ALSO
       MPI_Get_elements

Open MPI 1.2							  September 2006					   MPI_Get_count(3OpenMPI)