MPIGetelements(3OpenMPI) MPIGetelements(3OpenMPI)

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


SSYYNNTTAAXX
CC SSyynnttaaxx
       #include 
       int MPIGetelements(MPIStatus *status, MPIDatatype datatype,
            int *count)


FFoorrttrraann SSyynnttaaxx
       INCLUDE 'mpif.h'
       MPIGETELEMENTS(STATUS, DATATYPE, COUNT, IERROR)
            INTEGER   STATUS(MPISTATUSSIZE), DATATYPE, COUNT, IERROR


CC++++ SSyynnttaaxx
       #include 
       int Status::Getelements(const Datatype& datatype) const


IINNPPUUTT PPAARRAAMMEETTEERRSS
       status    Return status of receive operation (status).

       datatype  Datatype used by receive operation (handle).


OOUUTTPPUUTT PPAARRAAMMEETTEERRSS
       count     Number of received basic elements (integer).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPIGetelements behaves different from  MPIGetcount,  which  returns
       the  number  of  "top-level  entries"  received,  i.e.,  the  number of
       "copies" of type datatype. MPIGetcount may return any  integer  value
       k,  where  0 =< k =< count. If MPIGetcount returns k, then the number
       of basic elements received (and the  value  returned  by   MPIGetele-
       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 MPIGetcount returns the  value
       MPIUNDEFINED.

       EExxaammppllee:: Usage of MPIGetcount and MPIGetelement:

         ...
         CALL MPITYPECONTIGUOUS(2, MPIREAL, Type2, ierr)
         CALL MPITYPECOMMIT(Type2, ierr)
         ...
         CALL MPICOMMRANK(comm, rank, ierr)
         IF(rank.EQ.0) THEN
               CALL MPISEND(a, 2, MPIREAL, 1, 0, comm, ierr)
               CALL MPISEND(a, 3, MPIREAL, 1, 0, comm, ierr)
         ELSE
               CALL MPIRECV(a, 2, Type2, 0, 0, comm, stat, ierr)
               CALL MPIGETCOUNT(stat, Type2, i, ierr)     ! returns i=1
               CALL MPIGETELEMENTS(stat, Type2, i, ierr)  ! returns i=2
               CALL MPIRECV(a, 2, Type2, 0, 0, comm, stat, ierr)
               CALL MPIGETCOUNT(stat, Type2, i, ierr) ! returns i=MPIUNDEFINED
               CALL MPIGETELEMENTS(stat, Type2, i, ierr)  ! returns i=3
         END IF

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


EERRRROORRSS
       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::ERRORSTHROWEXCEPTIONS, 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
       MPICommseterrhandler; the predefined error handler MPIERRORSRETURN
       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
       MPIGetcount




Open MPI 1.2                    September 2006      MPIGetelements(3OpenMPI)