17.2.276. MPI_Pack_external_size

MPI_Pack_external_size — Calculates upper bound on space needed to write to a portable format SYNTAX C Syntax

#include <mpi.h>

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

! or the older form: INCLUDE 'mpif.h'

     CHARACTER*(*)   DATAREP 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

  • datarep: Data representation (string).

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

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

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

  • ierror: Fortran only: Error status (integer). 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). 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. ERRORS

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

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

  • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

  • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.

  • MPI_ERRORS_RETURN Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

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.

See the Error Handling section of the MPI-3.1 standard for more information.