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

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 the “Functionality” subsection of the “Caching” section in the “Groups,  Contexts,
       and Communicators” chapter in the MPI Standard).

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 the “Process Topologies” chapter in the MPI 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  return  result  of  the  function  and
       Fortran routines in the last argument.

       Before  the  error  value  is  returned,  the current MPI error handler associated with the communication
       object (e.g., communicator, window, file) is called.  If no communication object is associated  with  the
       MPI  call,  then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error
       handler.  When  MPI_COMM_SELF  is  not  initialized   (i.e.,   before   MPI_Init/MPI_Init_thread,   after
       MPI_Finalize,  or  when using the Sessions Model exclusively) the error raises the initial error handler.
       The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF  when  using
       the  World  model,  or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.  If no other appropriate error handler has been set, then the  MPI_ERRORS_RETURN
       error  handler  is  called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       SEE ALSO:
          MPI_Comm_dup_with_info

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                                   MPI_COMM_DUP(3)