SYNTAX

C Syntax

#include <mpi.h>
int MPI_Comm_idup(MPI_Comm comm, MPI_Comm *newcomm, MPI_Request *request)

Fortran Syntax

INCLUDE 'mpif.h'
MPI_COMM_IDUP(COMM, NEWCOMM, REQUEST, IERROR)
        INTEGER COMM, NEWCOMM, REQUEST, IERROR

INPUT PARAMETER

comm

Communicator (handle).

OUTPUT PARAMETERS

newcomm

Copy of comm (handle).

request

Communication request (handle).

IERROR

Fortran only: Error status (integer).

DESCRIPTION

MPI_Comm_idup starts the nonblocking duplication of an 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"). The communicator returned in newcomm will not be available until the request is complete.

The completion of a communicator duplication request can be determined by calling any of MPI_Wait, MPI_Waitany, MPI_Test, or MPI_Testany with the request returned by this function.

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_idup 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.