MPI_UNPACK, MPI_Unpack

Purpose

Unpacks the message into the specified receive buffer from the specified
packed buffer.

C synopsis

#include <mpi.h>
int MPI_Unpack(void* inbuf,int insize,int *position,void *outbuf,
               int outcount,MPI_Datatype datatype,MPI_Comm comm);

C++ synopsis

#include mpi.h
void MPI::Datatype::Unpack(const void* inbuf, int insize, void* outbuf,
                           int outcount, int& position,
                           const MPI::Comm& comm) const;

FORTRAN synopsis

include 'mpif.h' or use mpi
MPI_UNPACK(CHOICE INBUF,INTEGER INSIZE,INTEGER POSITION,CHOICE OUTBUF,
           INTEGER OUTCOUNT,INTEGER DATATYPE,INTEGER COMM,INTEGER IERROR)

Parameters

inbuf
     is the input buffer start (choice) (IN)

insize
     is an integer specifying the size of input buffer in bytes (IN)

position
     is an integer specifying the current packed buffer offset in bytes
     (INOUT)

outbuf
     is the output buffer start (choice) (OUT)

outcount
     is an integer specifying the number of instances of datatype to be
     unpacked (IN)

datatype
     is the datatype of each output data item (handle) (IN)

comm
     is the communicator for the packed message (handle) (IN)

IERROR
     is the FORTRAN return code. It is always the last argument.

Description

This subroutine unpacks the message specified by outbuf, outcount, and
datatype from the buffer space specified by inbuf and insize. The output
buffer is any receive buffer allowed in MPI_RECV. The input buffer is any
contiguous storage space containing insize bytes and starting at address
inbuf.

The input value of position is the beginning offset in the input buffer for
the data to be unpacked. The output value of position is the offset in the
input buffer following the data already unpacked. That is, the starting
point for another call to MPI_UNPACK. comm is the communicator that was
used to receive the packed message.

Notes

In MPI_UNPACK, the outcount argument specifies the actual number of items
to be unpacked. The size of the corresponding message is the increment in
position.

Errors

Invalid outcount
     outcount < 0

Invalid datatype

Type is not committed

Invalid communicator

Inbuf too small

Negative length or position for buffer
     outsize < 0 or position < 0

MPI not initialized

MPI already finalized

Related information