MPI_Comm_dup - Duplicates an existing communicator with all its cached
int MPI_Comm_dup(MPI_Comm comm, MPI_Comm *newcomm)
- - Communicator to be duplicated (handle)
- - A new communicator over the same group as comm but with a new
context. See notes. (handle)
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
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
. 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.
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.
All MPI routines in Fortran (except for MPI_WTIME
have an additional argument ierr
at the end of the argument list.
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
All MPI objects (e.g., MPI_Datatype
) are of type
All MPI routines (except MPI_Wtime
) 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 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
guarentee that an MPI program can continue past an error; however,
MPI implementations will attempt to continue whenever possible.
- - No error; MPI routine completed successfully.
- - Invalid communicator. A common error is to use a null communicator in a
call (not even allowed in MPI_Comm_rank ).
MPI_Comm_free, MPI_Keyval_create, MPI_Attr_put, MPI_Attr_delete,
MPI_Comm_create_keyval, MPI_Comm_set_attr, MPI_Comm_delete_attr