mpi_comm_dup(3openmpi) [osx man page]

MPI_Comm_dup(3OpenMPI)													    MPI_Comm_dup(3OpenMPI)

NAME

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

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Comm_dup(MPI_Comm comm, MPI_Comm *newcomm)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_COMM_DUP(COMM, NEWCOMM, IERROR)
	    INTEGER   COMM, NEWCOMM, IERROR

C++ Syntax
       #include <mpi.h>
       Intracomm Intracomm::Dup() const

       Intercomm Intercomm::Dup() const

INPUT PARAMETER

       comm	 Communicator (handle).

OUTPUT PARAMETERS

       newcomm	 Copy of comm (handle).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       MPI_Comm_dup  duplicates  the existing communicator comm with associated key values. For each key value, the respective copy callback func-
       tion determines the attribute value associated with this key in the new communicator; one particular action that a copy callback  may  take
       is to delete the attribute from the new communicator. Returns in newcomm a new communicator with the same group, any copied cached informa-
       tion, but a new context (see Section 5.7.1 of the MPI-1 Standard, "Functionality").

NOTES

       This operation is used to provide a parallel library call with a duplicate communication space that has the same properties as the original
       communicator.  This  includes  any attributes (see below) and topologies (see Chapter 6, "Process Topologies," in the MPI-1 Standard). This
       call is valid even if there are pending point-to-point communications involving the communicator comm. A  typical  call	might  involve	an
       MPI_Comm_dup at the beginning of the parallel call, and an MPI_Comm_free of that duplicated communicator at the end of the call. Other mod-
       els of communicator management are also possible.

       This call applies to both intra- and intercommunicators.

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++ func-
       tions  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.

Open MPI 1.2							  September 2006					    MPI_Comm_dup(3OpenMPI)

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 communication context but contains the same group of processes as the
       input communicator.  Since all MPI communication is performed within a communicator (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 information, 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 com-
       municator, 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)
       communicators that are given back to the user; the attibutes in this case can track subsequent MPI_Comm_dup operations on  this	communica-
       tor.

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  communicators), MPI_File_set_errhandler (for files), and
       MPI_Win_set_errhandler (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 whenever possible.

       MPI_SUCCESS
	      - No error; MPI routine completed successfully.
       MPI_ERR_COMM
	      - Invalid communicator.  A common error is to use a null communicator 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

       comm_dup.c

								     7/28/2010							   MPI_Comm_dup(3)