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MPI_Pack - Packs data of a given datatype into contiguous memory.
#include <mpi.h>
int MPI_Pack(const void *inbuf, int incount, MPI_Datatype datatype,
void *outbuf, int outsize, int *position, MPI_Comm comm)
INCLUDE ’mpif.h’
MPI_PACK(INBUF, INCOUNT, DATATYPE, OUTBUF,OUTSIZE, POSITION,
COMM, IERROR)
<type> INBUF(*), OUTBUF(*)
INTEGER INCOUNT, DATATYPE, OUTSIZE, POSITION, COMM, IERROR
#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).
- outbuf
- Output buffer start (choice).
- IERROR
- Fortran only: Error status (integer).
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)
}
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.
MPI_Unpack
MPI_Pack_size
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