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RedHat 9 (Linux i386) - man page for mpi_op_create (redhat section 3)

MPI_Op_create(3)			     LAM/MPI				 MPI_Op_create(3)

NAME
       MPI_Op_create -	Creates a user-defined combination function handle

SYNOPSIS
       #include <mpi.h>
       int MPI_Op_create(MPI_User_function func, int commute,
	   MPI_Op *pop)

INPUT PARAMETERS
       func   - user defined function (function)
       commute
	      - true if commutative;  false otherwise.

OUTPUT PARAMETER
       pop    - operation (handle)

NOTES ON THE USER FUNCTION
       The calling list for the user function type is

       typedef void (MPI_User_function) ( void * a,
       void * b, int * len, MPI_Datatype * );

       where the operation is b[i] = a[i] op b[i] , for i = 0, ... , len-1
	.   A  pointer	to  the  datatype  given to the MPI collective computation routine (i.e.,
       MPI_Reduce , MPI_Allreduce , MPI_Scan , or MPI_Reduce_scatter )	is  also  passed  to  the
       user-specified routine.

NOTES
       When  the MPI_Op created by this function is no longer being used, it should be freed with
       MPI_Op_free
	.

NOTES FOR FORTRAN
       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argu-
       ment ierr at the end of the argument list.  ierr is an integer and has the same meaning as
       the return value of the routine in C.  In Fortran, MPI routines are subroutines,  and  are
       invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

NOTES ON COLLECTIVE OPERATIONS
       The  reduction  functions  (  MPI_Op  ) do not return an error value.  As a result, if the
       functions detect an error, all they can do is either call MPI_Abort or silently	skip  the
       problem.   Thus,  if  you  change the error handler from MPI_ERRORS_ARE_FATAL to something
       else (e.g., MPI_ERRORS_RETURN ), then no error may be indicated.

       The reason for this is the performance problems that arise in ensuring that all collective
       routines return the same error value.

ERRORS
       If  an  error occurs in an MPI function, the current MPI error handler is called to handle
       it.  By default, this error handler aborts the MPI job.	The error handler may be  changed
       with  MPI_Errhandler_set  ;  the predefined error handler MPI_ERRORS_RETURN may be used to
       cause error values to be returned (in C and Fortran; this error handler is less useful  in
       with  the  C++  MPI  bindings.	The predefined error handler MPI::ERRORS_THROW_EXCEPTIONS
       should be used in C++ if the error value needs to be recovered).  Note that MPI	does  not
       guarantee that an MPI program can continue past an error.

       All  MPI  routines  (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as
       the value of the function and Fortran routines in the last argument.  The C++ bindings for
       MPI  do not return error values; instead, error values are communicated by throwing excep-
       tions of type MPI::Exception (but not by default).  Exceptions  are  only  thrown  if  the
       error value is not MPI::SUCCESS
	.

       Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return
       upon an error, there will be no way to recover what the actual error value was.
       MPI_SUCCESS
	      - No error; MPI routine completed successfully.
       MPI_ERR_OP
	      - Invalid operation.  MPI operations (objects of type MPI_Op ) must either  be  one
	      of the predefined operations (e.g., MPI_SUM ) or created with MPI_Op_create
	       .   Additionally,  only	certain datatypes are alloed with given predefined opera-
	      tions.  See MPI-1, section 4.9.2.
       MPI_ERR_ARG
	      - Invalid argument.  Some argument is invalid and is not identified by  a  specific
	      error class.  This is typically a NULL pointer or other such error.
       MPI_ERR_OTHER
	      -  This error is returned when some part of the LAM/MPI implementation is unable to
	      acquire memory.

SEE ALSO
       MPI_Op_free

MORE INFORMATION
       For more information, please see the official MPI Forum web site, which contains the  text
       of both the MPI-1 and MPI-2 standards.  These documents contain detailed information about
       each MPI function (most of which is not duplicated in these man pages).

       http://www.mpi-forum.org/

ACKNOWLEDGEMENTS
       The LAM Team would like the thank the MPICH Team for the handy  program	to  generate  man
       pages  ("doctext"  from ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the initial for-
       matting, and some initial text for most of the MPI-1 man pages.

LOCATION
       opcreate.c

LAM/MPI 6.5.8				    11/10/2002				 MPI_Op_create(3)


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