MPI_Pack_external_size(3) Open MPI MPI_Pack_external_size(3)
NAME
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(char *datarep, int incount,
MPI_Datatype datatype, MPI_Aint *size)
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
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
C++ Syntax
#include <mpi.h>
MPI::Aint MPI::Datatype::Pack_external_size(const char* datarep,
int incount) const
INPUT PARAMETERS
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 posi-
tion that would occur in a call to MPI_Pack_external with the same val-
ues for datarep, incount, and datatype.
The call returns an upper bound, rather than an exact bound, as the ex-
act 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 value
of the function and Fortran routines in the last argument. C++ func-
tions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
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.
SEE ALSO
MPI_Pack_external
MPI_Unpack_external
4.1.2 Nov 24, 2021 MPI_Pack_external_size(3)
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