Provided by: lam-mpidoc_7.1.4-7.2_all 
NAME
MPI_Unpack - Unpack a datatype into contiguous memory
SYNOPSIS
#include <mpi.h>
int MPI_Unpack(void *packbuf, int packsize, int *packpos,
void *buf, int count, MPI_Datatype dtype,
MPI_Comm comm)
INPUT PARAMETERS
packbuf
- input buffer start (choice)
packsize
- size of input buffer, in bytes (integer)
count - number of items to be unpacked (integer)
dtype - datatype of each output data item (handle)
comm - communicator for packed message (handle)
INPUT/OUTPUT PARAMETERS
packpos
- current position in bytes (integer)
OUTPUT PARAMETER
buf - output buffer start (choice)
NOTES FOR FORTRAN
All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
end of the argument list. ierr is an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.
All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.
ERRORS
If an error occurs in an MPI function, the current MPI error handler is called to handle it. By default,
this error handler aborts the MPI job. The error handler may be changed with MPI_Errhandler_set ; the
predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned (in C and
Fortran; this error handler is less useful in with the C++ MPI bindings. The predefined error handler
MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value needs to be recovered). Note that
MPI does not guarantee that an MPI program can continue past an error.
All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the
function and Fortran routines in the last argument. The C++ bindings for MPI do not return error values;
instead, error values are communicated by throwing exceptions of type MPI::Exception (but not by
default). Exceptions are only thrown if the error value is not MPI::SUCCESS .
Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return upon an error,
there will be no way to recover what the actual error value was.
MPI_SUCCESS
- No error; MPI routine completed successfully.
MPI_ERR_COMM
- Invalid communicator. A common error is to use a null communicator in a call (not even allowed
in MPI_Comm_rank ).
MPI_ERR_COUNT
- Invalid count argument. Count arguments must be non-negative; a count of zero is often valid.
MPI_ERR_TYPE
- Invalid datatype argument. May be an uncommitted MPI_Datatype (see MPI_Type_commit ).
MPI_ERR_ARG
- Invalid argument. Some argument is invalid and is not identified by a specific error class.
This is typically a NULL pointer or other such error.
MPI_ERR_BUFFER
- Invalid buffer pointer. Usually a null buffer where one is not valid.
MPI_ERR_TRUNCATE
- Message truncated on receive. The buffer size specified was too small for the received message.
This is a recoverable error in the LAM/MPI implementation.
SEE ALSO
MPI_Pack, MPI_Pack_size
MORE INFORMATION
For more information, please see the official MPI Forum web site, which contains the text of both the
MPI-1 and MPI-2 standards. These documents contain detailed information about each MPI function (most of
which is not duplicated in these man pages).
http://www.mpi-forum.org/
ACKNOWLEDGEMENTS
The LAM Team would like the thank the MPICH Team for the handy program to generate man pages ("doctext"
from ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the initial formatting, and some initial text for
most of the MPI-1 man pages.
LOCATION
unpack.c