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MPI_Pack_size_c(3) MPI MPI_Pack_size_c(3)


MPI_Pack_size_c - Returns the upper bound on the amount of space needed to pack a message


int QMPI_Pack_size_c(QMPI_Context context, int tool_id, MPI_Count incount, MPI_Datatype datatype,
MPI_Comm comm, MPI_Count *size) MPICH_API_PUBLIC


- count argument to packing call (non-negative integer) (non-negative integer)
- datatype argument to packing call (handle) (handle)
- communicator argument to packing call (handle) (handle)


- upper bound on size of packed message, in bytes (non-negative integer) (non-negative integer)


The MPI standard document describes this in terms of MPI_Pack , but it applies to both MPI_Pack and MPI_Unpack . That is, the value size is the maximum that is needed by either MPI_Pack or MPI_Unpack .


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.


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.


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.

- No error; MPI routine completed successfully.

- Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK ).
- Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank ).
- Invalid count argument. Count arguments must be non-negative; a count of zero is often valid.
- Invalid datatype argument. Additionally, this error can occur if an uncommitted MPI_Datatype (see MPI_Type_commit ) is used in a communication call.
- Other error; use MPI_Error_string to get more information about this error code.