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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 argument provided by the receive call that set  the  status  vari-able. variable.
       able.  (As explained in Section 3.12.5 in the MPI-1 Standard, "Use of General Datatypes in Communica-tion," Communication,"
       tion," 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
       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





Open MPI 1.2                                   September 2006                        MPI_Get_count(3OpenMPI)