osx man page for mpi_get_elements

MPI_Get_elements(3OpenMPI)												MPI_Get_elements(3OpenMPI)

NAME
       MPI_Get_elements  - Returns the number of basic elements in a data type.

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

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

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

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

       datatype  Datatype used by receive operation (handle).

OUTPUT PARAMETERS
       count	 Number of received basic elements (integer).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION
       MPI_Get_elements  behaves  different  from  MPI_Get_count,  which  returns  the number of "top-level entries" received, i.e., the number of
       "copies" of type datatype. MPI_Get_count may return any integer value k, where 0 =< k =< count. If MPI_Get_count returns k, then the number
       of  basic elements received (and the value returned by  MPI_Get_elements) is n * k, where n is the number of basic elements in the type map
       of datatype. If the number of basic elements received is not a multiple of n, that is, if the receive operation has not received  an  inte-
       gral number of datatype "copies," then MPI_Get_count returns the value MPI_UNDEFINED.

       Example: Usage of MPI_Get_count and MPI_Get_element:

	 ...
	 CALL MPI_TYPE_CONTIGUOUS(2, MPI_REAL, Type2, ierr)
	 CALL MPI_TYPE_COMMIT(Type2, ierr)
	 ...
	 CALL MPI_COMM_RANK(comm, rank, ierr)
	 IF(rank.EQ.0) THEN
	       CALL MPI_SEND(a, 2, MPI_REAL, 1, 0, comm, ierr)
	       CALL MPI_SEND(a, 3, MPI_REAL, 1, 0, comm, ierr)
	 ELSE
	       CALL MPI_RECV(a, 2, Type2, 0, 0, comm, stat, ierr)
	       CALL MPI_GET_COUNT(stat, Type2, i, ierr)     ! returns i=1
	       CALL MPI_GET_ELEMENTS(stat, Type2, i, ierr)  ! returns i=2
	       CALL MPI_RECV(a, 2, Type2, 0, 0, comm, stat, ierr)
	       CALL MPI_GET_COUNT(stat, Type2, i, ierr) ! returns i=MPI_UNDEFINED
	       CALL MPI_GET_ELEMENTS(stat, Type2, i, ierr)  ! returns i=3
	 END IF

       The  function MPI_Get_elements can also be used after a probe to find the number of elements in the probed message. Note that the two func-
       tions MPI_Get_count and MPI_Get_elements return the same values when they are used with primitive data types.

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_count

Open MPI 1.2							  September 2006					MPI_Get_elements(3OpenMPI)