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MPI_Comm_dup(3)			      MPI		       MPI_Comm_dup(3)

NAME
       MPI_Comm_dup -  Duplicates an existing communicator with	all its	cached
       information

SYNOPSIS
       int MPI_Comm_dup(MPI_Comm comm, MPI_Comm	*newcomm)

INPUT PARAMETER
       comm   -	Communicator to	be duplicated (handle)

OUTPUT PARAMETER
       newcomm
	      -	A new communicator over	the same group as comm but with	a  new
	      context. See notes.  (handle)

NOTES
       This routine is used to create a	new communicator that has a new	commu-
       nication	context	but contains the same group of processes as the	 input
       communicator.  Since all	MPI communication is performed within a	commu-
       nicator (specifies as the group of processes plus  the  context),  this
       routine	provides an effective way to create a private communicator for
       use by a	software module	or library.  In	particular, no library routine
       should  use MPI_COMM_WORLD as the communicator; instead,	a duplicate of
       a user-specified	communicator should always be used.  For more informa-
       tion, see Using MPI, 2nd	edition.

       Because	this routine essentially produces a copy of a communicator, it
       also copies any attributes that have been defined on the	input communi-
       cator, using the	attribute copy function	specified by the copy_function
       argument	to MPI_Keyval_create .	This is	particularly  useful  for  (a)
       attributes that describe	some property of the group associated with the
       communicator, such as its interconnection topology and  (b)  communica-
       tors  that  are	given back to the user;	the attibutes in this case can
       track subsequent	MPI_Comm_dup operations	on this	communicator.

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.

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_COMM
	      -	 Invalid communicator.	A common error is to use a null	commu-
	      nicator in a call	(not even allowed in MPI_Comm_rank ).

SEE ALSO
       MPI_Comm_free, MPI_Keyval_create, MPI_Attr_put, MPI_Attr_delete,
       MPI_Comm_create_keyval, MPI_Comm_set_attr, MPI_Comm_delete_attr

LOCATION
       src/mpi/comm/comm_dup.c

				   9/20/2012		       MPI_Comm_dup(3)

NAME | SYNOPSIS | INPUT PARAMETER | OUTPUT PARAMETER | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | SEE ALSO | LOCATION

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