mpi_comm_dup(3openmpi) [osx man page]
MPI_Comm_dup(3OpenMPI) MPI_Comm_dup(3OpenMPI) NAME
MPI_Comm_dup - Duplicates an existing communicator with all its cached information. SYNTAX
C Syntax #include <mpi.h> int MPI_Comm_dup(MPI_Comm comm, MPI_Comm *newcomm) Fortran Syntax INCLUDE 'mpif.h' MPI_COMM_DUP(COMM, NEWCOMM, IERROR) INTEGER COMM, NEWCOMM, IERROR C++ Syntax #include <mpi.h> Intracomm Intracomm::Dup() const Intercomm Intercomm::Dup() const INPUT PARAMETER
comm Communicator (handle). OUTPUT PARAMETERS
newcomm Copy of comm (handle). IERROR Fortran only: Error status (integer). DESCRIPTION
MPI_Comm_dup duplicates the existing communicator comm with associated key values. For each key value, the respective copy callback func- tion determines the attribute value associated with this key in the new communicator; one particular action that a copy callback may take is to delete the attribute from the new communicator. Returns in newcomm a new communicator with the same group, any copied cached informa- tion, but a new context (see Section 5.7.1 of the MPI-1 Standard, "Functionality"). NOTES
This operation is used to provide a parallel library call with a duplicate communication space that has the same properties as the original communicator. This includes any attributes (see below) and topologies (see Chapter 6, "Process Topologies," in the MPI-1 Standard). This call is valid even if there are pending point-to-point communications involving the communicator comm. A typical call might involve an MPI_Comm_dup at the beginning of the parallel call, and an MPI_Comm_free of that duplicated communicator at the end of the call. Other mod- els of communicator management are also possible. This call applies to both intra- and intercommunicators. ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func- tions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object. Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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. Open MPI 1.2 September 2006 MPI_Comm_dup(3OpenMPI)
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MPI_Comm_dup(3) MPI MPI_Comm_dup(3) 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 PARAMETER
comm - Communicator to be duplicated (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 com- municator, 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 communica- tor. 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 LOCATION
comm_dup.c 7/28/2010 MPI_Comm_dup(3)