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MPI_Pack(3) man page (version 1.3.4)

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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 ele-
       ments, 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
           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

1.3.4                            Nov 11, 2009                      MPI_Pack(3)

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