NAME

       MPI_Comm_dup -  Duplicates an existing communicator

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

                                                    2/9/2024                                     MPI_Comm_dup(3)