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

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_DUP(COMM, NEWCOMM, IERROR)
	INTEGER	COMM, NEWCOMM, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Comm_dup(comm, newcomm, ierror)
	TYPE(MPI_Comm), INTENT(IN) :: comm
	TYPE(MPI_Comm), INTENT(OUT) :: newcomm
	INTEGER, OPTIONAL, INTENT(OUT) :: 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 function 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 information, 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 models of communicator management are also possible.

This call applies to both intra- and intercommunicators.

Note that it is not defined by the MPI standard what happens if the attribute copy callback invokes other MPI functions. In Open MPI, it is not valid for attribute copy callbacks (or any of their children) to add or delete attributes on the same object on which the attribute copy callback is being invoked.

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++ functions 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.