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)
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