Poster of Linux kernelThe best gift for a Linux geek
MPI_Get_count

MPI_Get_count

Section: Open MPI (3) Updated: Oct 05, 2010
Local index Up
 

NAME

MPI_Get_count - Gets the number of top-level elements received.

 

SYNTAX

 

C Syntax

#include <mpi.h>
int MPI_Get_count(MPI_Status *status, MPI_Datatype datatype,
        int *count)

 

Fortran Syntax

INCLUDE 'mpif.h'
MPI_GET_COUNT(STATUS, DATATYPE, COUNT, IERROR)
        INTEGER STATUS(MPI_STATUS_SIZE), DATATYPE, COUNT, IERROR 

 

C++ Syntax

#include <mpi.h>
int Status::Get_count(const Datatype& datatype) const

 

INPUT PARAMETERS

status
Return status of receive operation (status).
datatype
Datatype of each receive buffer element (handle).

 

OUTPUT PARAMETERS

count
Number of received elements (integer).
IERROR
Fortran only: Error status (integer).

 

DESCRIPTION

Returns the number of entries received. (We count entries, each of type datatype, not bytes.) The datatype argument should match the argument provided by the receive call that set the status variable. (As explained in Section 3.12.5 in the MPI-1 Standard, "Use of General Datatypes in Communication," MPI_Get_count may, in certain situations, return the value MPI_UNDEFINED.)

The datatype argument is passed to MPI_Get_count to improve performance. A message might be received without counting the number of elements it contains, and the count value is often not needed. Also, this allows the same function to be used after a call to MPI_Probe.

 

NOTES

If the size of the datatype is zero, this routine will return a count of zero. If the amount of data in status is not an exact multiple of the size of datatype (so that count would not be integral), a count of MPI_UNDEFINED is returned instead.

 

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++ functions 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 ALSO

MPI_Get_elements


 

Index

NAME
SYNTAX
C Syntax
Fortran Syntax
C++ Syntax
INPUT PARAMETERS
OUTPUT PARAMETERS
DESCRIPTION
NOTES
ERRORS
SEE ALSO

This document was created by man2html, using the manual pages.
Time: 21:50:38 GMT, April 16, 2011