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
- 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).
- 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.
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++ 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