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 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.

SEE ALSO

       MPI_Comm_dup_with_info
       MPI_Comm_idup