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, start-
       ing  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. position 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 argument 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++ 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_Unpack
       MPI_Pack_size

Open MPI 1.2							  September 2006						MPI_Pack(3OpenMPI)