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 PARAMETERS

       comm   - Communicator to be duplicated (handle)

OUTPUT PARAMETERS

       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 communicator, 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 communicator.

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

                                            11/12/2016                            MPI_Comm_dup(3)