17.2.275. MPI_Pack_size

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

17.2.275.1. SYNTAX

17.2.275.1.1. C Syntax

#include <mpi.h>

int MPI_Pack_size(int incount, MPI_Datatype datatype, MPI_Comm comm,
     int *size)

17.2.275.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_PACK_SIZE(INCOUNT, DATATYPE, COMM, SIZE, IERROR)
     INTEGER INCOUNT, DATATYPE, COMM, SIZE, IERROR

17.2.275.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Pack_size(incount, datatype, comm, size, ierror)
     INTEGER, INTENT(IN) :: incount
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Comm), INTENT(IN) :: comm
     INTEGER, INTENT(OUT) :: size
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.275.2. INPUT PARAMETERS

  • incount: Count argument to packing call (integer).

  • datatype: Datatype argument to packing call (handle).

  • comm: Communicator argument to packing call (handle).

17.2.275.3. OUTPUT PARAMETERS

  • size: Upper bound on size of packed message, in bytes (integer).

  • IERROR: Fortran only: Error status (integer).

17.2.275.4. DESCRIPTION

MPI_Pack_size allows the application to find out how much space is needed to pack a message. A call to MPI_Pack_size(incount, datatype, comm, size) returns in size an upper bound on the increment in position that would occur in a call to MPI_Pack, with the same values for incount, datatype, and comm.

Rationale: The call returns an upper bound, rather than an exact bound, since the exact amount of space needed to pack the message may depend on the context (e.g., first message packed in a packing unit may take more space).

17.2.275.5. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

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.

See also

MPI_Pack MPI_Unpack