Is there any place that this can actually be used? It's a fairly large change to the RTE interface (which we should try to keep stable), and I can't convince myself that it's useful; in general, if a BTL or MTL is asking for a piece of data, the MPI library is stuck until that data's available. I can see doing some lazy approach, but I can't see making the modex_recv call non-blocking.
Brian On 1/11/14 9:28 PM, "Ralph Castain" <r...@open-mpi.org> wrote: >NOTE: This will involve a change to the MPI-RTE interface > >WHAT: Modify modex_recv to add a callback function that will return the >requested data when it is available > >WHY: Enable faster startup on large scale systems by eliminating the >current mandatory modex barrier during MPI_Init > >HOW: The ompi_modex_recv functions will have callback function and >(void*)cbdata arguments added to them. > An ompi_modex_recv_t struct will be defined that includes a >pointer to the returned data plus a "bool active" > that can be used to detect when the data has been returned >if blocking is required. > > When a modex_recv is issued, ORTE will check for the >presence of the requested data and immediately > issue a callback if the data is available. If the data is >not available, then ORTE will request the data from > the remote process, and execute the callback when the >remote process returns it. > > The current behavior of a blocking modex barrier will >remain the default - the new behavior will only take affect > if specifically requested by the user via MCA param. With >this new behavior, the current call to "modex" in > MPI_Init will become a "no-op" when the processes are >launched via mpirun - this will be executed in ORTE > so that other RTEs that do not wish to support async modex >behavior are not impacted. > >WHEN: No hurry on this as it is intended for 1.9, so let's say mid Feb. >Info on a branch will be made available in > the near future. > > >_______________________________________________ >devel mailing list >de...@open-mpi.org >http://www.open-mpi.org/mailman/listinfo.cgi/devel > -- Brian W. Barrett Scalable System Software Group Sandia National Laboratories
