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MPI_Intercomm_create(3)		      MPI	       MPI_Intercomm_create(3)

NAME
       MPI_Intercomm_create  -	Creates	an intercommuncator from two intracom-
       municators

SYNOPSIS
       int MPI_Intercomm_create(MPI_Comm local_comm, int local_leader,
			      MPI_Comm peer_comm, int remote_leader, int tag,
			      MPI_Comm *newintercomm)

INPUT PARAMETERS
       local_comm
	      -	Local (intra)communicator
       local_leader
	      -	Rank in	local_comm of leader (often 0)
       peer_comm
	      -	Communicator used to communicate between a designated  process
	      in  the  other communicator.  Significant	only at	the process in
	      local_comm with rank local_leader	.

       remote_leader
	      -	Rank in	peer_comm of remote leader (often 0)
       tag    -	Message	tag to use in constructing intercommunicator; if  mul-
	      tiple MPI_Intercomm_creates are being made, they should use dif-
	      ferent tags (more	precisely, ensure that the  local  and	remote
	      leaders  are  using different tags for each MPI_intercomm_create
	      ).

OUTPUT PARAMETER
       comm_out
	      -	Created	intercommunicator

NOTES
       peer_comm is significant	 only  for  the	 process  designated  the  lo-
       cal_leader in the local_comm .

       The  MPI	 1.1  Standard contains	two mutually exclusive comments	on the
       input intercommunicators.  One says that	their repective	groups must be
       disjoint;  the  other  that the leaders can be the same process.	 After
       some discussion by the MPI Forum, it has	been decided that  the	groups
       must  be	disjoint.  Note	that the reason	given for this in the standard
       is not the reason for this choice; rather, the other operations on  in-
       tercommunicators	 (like	MPI_Intercomm_merge ) do not make sense	if the
       groups are not disjoint.

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 ).
       MPI_ERR_TAG
	      -	Invalid	tag argument.  Tags must be non-negative;  tags	 in  a
	      receive  (  MPI_Recv , MPI_Irecv , MPI_Sendrecv ,	etc.) may also
	      be MPI_ANY_TAG .	The largest tag	value is available through the
	      the attribute MPI_TAG_UB .

       MPI_ERR_INTERN
	      -	This error is returned when some part of the MPICH implementa-
	      tion is unable to	acquire	memory.
       MPI_ERR_RANK
	      -	Invalid	source or destination rank.   Ranks  must  be  between
	      zero  and	the size of the	communicator minus one;	ranks in a re-
	      ceive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also  be
	      MPI_ANY_SOURCE .

SEE ALSO
       MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group,
       MPI_Comm_remote_size

LOCATION
       src/mpi/comm/intercomm_create.c

				   9/20/2012	       MPI_Intercomm_create(3)

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

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