On Jul 18, 2013, at 7:05 AM, David Goodell (dgoodell) <dgood...@cisco.com> wrote:
> On Jul 18, 2013, at 8:06 AM, Ralph Castain <r...@open-mpi.org> wrote: > >> That's a good point, and a bad behavior. IIRC, it results from the MPI >> Forum's adoption of the MPI-T requirement that stipulates we must allow >> access to all control and performance variables at startup so they can be >> externally seen/manipulated. > > Minor nit: MPI_T does not require this. However, it does recommend that you > offer users access to as many variables as possible as early as reasonably > possible for the convenience and control of the user. > > If an implementation chooses to offer 5% of the possible control/performance > variables to the user just before MPI_Finalize, that's still a valid MPI_T > implementation. But it may not be a very useful one... The problem here is one of use vs startup performance. George is quite correct with his concerns - this behavior would have been a serious problem for RoadRunner, for example, where we had a small IO channel feeding a lot of nodes. It will definitely become an issue at exascale where IO bandwidth and memory will be at a premium. This is especially troubling when you consider how few people will ever use this capability. Perhaps we should offer a switch that says "I want access to MPI-T" so that the rest of the world isn't hammered by this kind of behavior? > > -Dave > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel
