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MPI_Get_elements(3) man page (version 1.2.9)

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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_ele-
       ments)  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 mul-
       tiple 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

       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)

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