MPI_Comm_dup
Duplicates an existing communicator with all its cached information
Synopsis
#include "mpi.h"
int MPI_Comm_dup (
MPI_Comm comm,
MPI_Comm *comm_out )
Input Parameter
- comm
- communicator (handle)
Output Parameter
- 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.
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_Errhandler_set; 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.
- 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).
- MPI_ERR_INTERN
- This error is returned when some part of the MPICH
implementation is unable to acquire memory.
See Also
MPI_Comm_free, MPI_Keyval_create, MPI_Attr_set, MPI_Attr_delete
Location:comm_dup.c