Synopsis

int MPI_Unpack(const void *inbuf, int insize, int *position, void *outbuf,
               int outcount, MPI_Datatype datatype, MPI_Comm comm)
int MPI_Unpack_c(const void *inbuf, MPI_Count insize, MPI_Count *position,
                 void *outbuf, MPI_Count outcount, MPI_Datatype datatype,
                 MPI_Comm comm)

Input Parameters

inbuf

input buffer start (choice)

insize

size of input buffer, in bytes (non-negative integer)

outcount

number of items to be unpacked (integer)

datatype

datatype of each output data item (handle)

comm

communicator for packed message (handle)

Input/Output Parameters

position

current position in bytes (integer)

Output Parameters

outbuf

output buffer start (choice)

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as 'malloc' or other non-MPICH runtime routines that are themselves not interrupt-safe.

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

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. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with 'MPI_Comm_set_errhandler' (for communicators), 'MPI_File_set_errhandler' (for files), and 'MPI_Win_set_errhandler' (for RMA windows). The MPI-1 routine 'MPI_Errhandler_set' may be used but its use is deprecated. 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; however, MPI implementations will attempt to continue whenever possible.

  • MPI_SUCCESS - No error; MPI routine completed successfully.

  • MPI_ERR_ARG - Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., 'MPI_ERR_RANK').

  • 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. Additionally, this error can occur if an uncommitted MPI_Datatype (see 'MPI_Type_commit') is used in a communication call.

  • MPI_ERR_OTHER - Other error; use 'MPI_Error_string' to get more information about this error code.

See also

MPI_Pack(3) MPI_Pack_size(3)