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MPI_Comm_compare(3)		      MPI		   MPI_Comm_compare(3)

NAME
       MPI_Comm_compare	-  Compares two	communicators

SYNOPSIS
       int MPI_Comm_compare(MPI_Comm comm1, MPI_Comm comm2, int	*result)

INPUT PARAMETERS
       comm1  -	comm1 (handle)
       comm2  -	comm2 (handle)

OUTPUT PARAMETER
       result -	 integer which is MPI_IDENT if the contexts and	groups are the
	      same, MPI_CONGRUENT if different contexts	but identical  groups,
	      MPI_SIMILAR  if  different  contexts  but	 similar  groups,  and
	      MPI_UNEQUAL otherwise

USING 'MPI_COMM_NULL' WITH 'MPI_COMM_COMPARE'
       It is an	error  to  use	MPI_COMM_NULL  as  one	of  the	 arguments  to
       MPI_Comm_compare	.  The relevant	sections of the	MPI standard are

       .  (2.4.1 Opaque	Objects) A null	handle argument	is an erroneous	IN ar-
       gument in MPI calls, unless an exception	is explicitly  stated  in  the
       text that defines the function.

       .    (5.4.1.   Communicator  Accessors)	where  there  is  no  text  in
       MPI_COMM_COMPARE	allowing a null	handle.

THREAD AND INTERRUPT SAFETY
       This routine is thread-safe.  This  means  that	this  routine  may  be
       safely  used by multiple	threads	without	the need for any user-provided
       thread locks.  However, the routine is not interrupt safe.   Typically,
       this  is	due to the use of memory allocation routines such as malloc or
       other non-MPICH runtime routines	that  are  themselves  not  interrupt-
       safe.  (To perform the communicator comparisions, this routine may need
       to allocate some	memory.	 Memory	allocation is not interrupt-safe,  and
       hence this routine is only thread-safe.)

NOTES FOR FORTRAN
       All  MPI	routines in Fortran (except for	MPI_WTIME and MPI_WTICK	) have
       an additional argument 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.

ERRORS
       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.  Before the value is returned, the current MPI error
       handler	is called.  By default,	this error handler aborts the MPI job.
       The error handler may be	changed	with MPI_Comm_set_errhandler (for com-
       municators),  MPI_File_set_errhandler  (for files), and MPI_Win_set_er-
       rhandler	(for RMA windows).  The	MPI-1 routine  MPI_Errhandler_set  may
       be  used	 but  its  use	is  deprecated.	  The predefined error handler
       MPI_ERRORS_RETURN may be	used to	cause error  values  to	 be  returned.
       Note  that MPI does not guarentee that an MPI program can continue past
       an error; however, MPI implementations will attempt to  continue	 when-
       ever possible.

       MPI_SUCCESS
	      -	No error; MPI routine completed	successfully.
       MPI_ERR_ARG
	      -	Invalid	argument.  Some	argument is invalid and	is not identi-
	      fied by a	specific error class (e.g., MPI_ERR_RANK ).

LOCATION
       src/mpi/comm/comm_compare.c

				   9/20/2012		   MPI_Comm_compare(3)

NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETER | USING 'MPI_COMM_NULL' WITH 'MPI_COMM_COMPARE' | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | LOCATION

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