17.2.274. MPI_Pack_external_size

MPI_Pack_external_size - Calculates upper bound on space needed to write to a portable format

17.2.274.1. SYNTAX

17.2.274.1.1. C Syntax

#include <mpi.h>

int MPI_Pack_external_size(const char *datarep, int incount,
     MPI_Datatype datatype, MPI_Aint *size)

17.2.274.1.2. Fortran Syntax

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

     INTEGER         INCOUNT, DATATYPE, IERROR
     INTEGER(KIND=MPI_ADDRESS_KIND) SIZE
     CHARACTER*(*)   DATAREP

17.2.274.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Pack_external_size(datarep, incount, datatype, size, ierror)
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     INTEGER, INTENT(IN) :: incount
     CHARACTER(LEN=*), INTENT(IN) :: datarep
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: size
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.274.2. INPUT PARAMETERS

  • datarep: Data representation (string).

  • incount: Number of input data items (integer).

  • datatype: Datatype of each input data item (handle).

17.2.274.3. OUTPUT PARAMETERS

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

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

17.2.274.4. DESCRIPTION

MPI_Pack_external_size allows the application to find out how much space is needed to pack a message in the portable format defined by the MPI Forum. It returns in size an upper bound on the increment in position that would occur in a call to MPI_Pack_external with the same values for datarep, incount, and datatype.

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

17.2.274.5. NOTES

The datarep argument specifies the data format. The only valid value in the current version of MPI is “external32”. The argument is provided for future extensibility.

17.2.274.6. 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 the MPI man page for a full list of MPI error codes.