NAME

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

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Get_count(const 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 argument 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 elements 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

       If the value to be  returned  is  larger  than  can  fit  into  the  count  parameter,  an
       MPI_ERR_TRUNCATE exception is invoked.

       Almost all MPI routines return an error value; C routines as the value of the function and
       Fortran routines in the last argument. C++ functions 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