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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 (handle)

OUTPUT PARAMETERS

       newcomm
              - copy of comm (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 attributes 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 guarantee 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_ARG
              -  Invalid  argument.  Some argument is invalid and is not identified by a specific
              error class (e.g., MPI_ERR_RANK ).
       MPI_ERR_COMM
              - Invalid communicator.  A common error is to use a null  communicator  in  a  call
              (not even allowed in MPI_Comm_rank ).
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

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

                                            2/22/2022                             MPI_Comm_dup(3)