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MPI_Pack(3OpenMPI)                                                                        MPI_Pack(3OpenMPI)



NAME
       MPI_Pack - Packs data of a given datatype into contiguous memory.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Pack(void *inbuf, int incount, MPI_Datatype datatype,
            void *outbuf, int outsize, int *position, MPI_Comm comm)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_PACK(INBUF, INCOUNT, DATATYPE, OUTBUF,OUTSIZE, POSITION,
                 COMM, IERROR)
            <type>    INBUF(*), OUTBUF(*)
            INTEGER   INCOUNT, DATATYPE, OUTSIZE, POSITION, COMM, IERROR


C++ Syntax
       #include <mpi.h>
       void Datatype::Pack(const void* inbuf, int incount, void *outbuf,
            int outsize, int& position, const Comm &comm) const


INPUT PARAMETERS
       inbuf     Input buffer start (choice).

       incount   Number of input data items (integer).

       datatype  Datatype of each input data item (handle).

       outsize   Output buffer size, in bytes (integer).

       comm      Communicator for packed message (handle).


INPUT/OUTPUT PARAMETER
       position  Current position in buffer, in bytes (integer).


OUTPUT PARAMETERS
       outbuf    Output buffer start (choice).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       Packs  the  message  in  the  send buffer specified by inbuf, incount, datatype into the buffer space
       specified by outbuf and outsize. The  input  buffer  can  be  any  communication  buffer  allowed  in
       MPI_Send.  The  output  buffer is a contiguous storage area containing outsize bytes, starting at the
       address outbuf (length is counted in bytes, not elements, as if it were a communication buffer for  a
       message of type MPI_Packed).

       The  input value of position is the first location in the output buffer to be used for packing. posi-tion position
       tion is incremented by the size of the packed message, and the output value of position is the  first
       location  in the output buffer following the locations occupied by the packed message. The comm argu-ment argument
       ment is the communicator that will be subsequently used for sending the packed message.

       Example: An example using MPI_Pack:

           int position, i, j, a[2];
           char buff[1000];

           ....

           MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
           if (myrank == 0)
           {
              / * SENDER CODE */

           position = 0;
             MPI_Pack(&i, 1, MPI_INT, buff, 1000, &position, MPI_COMM_WORLD);
             MPI_Pack(&j, 1, MPI_INT, buff, 1000, &position, MPI_COMM_WORLD);
             MPI_Send( buff, position, MPI_PACKED, 1, 0, MPI_COMM_WORLD);
           }
           else  /* RECEIVER CODE */
             MPI_Recv( a, 2, MPI_INT, 0, 0, MPI_COMM_WORLD)

           }


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_Unpack
       MPI_Pack_size




Open MPI 1.2                                   September 2006                             MPI_Pack(3OpenMPI)