No specific test, just an idea how this might impact an app. I am guessing it won't even be noticable.
Rich ----- Original Message ----- From: devel-boun...@open-mpi.org <devel-boun...@open-mpi.org> To: Open MPI Developers <de...@open-mpi.org> Sent: Thu Dec 18 07:13:08 2008 Subject: Re: [OMPI devel] RFC: make predefined handles extern to pointers Richard Graham wrote: > Terry, > Is there any way you can quantify the cost ? This seems reasonable, but > would be nice to get an idea what the performance cost is (and not within a > tight loop where everything stays in cache). > > Rich > > > Ok, I guess that would eliminate any of the simple perf tests like IMB, netperf, and such. So do you have something else in mind, maybe HPCC? --td > On 12/16/08 10:41 AM, "Terry D. Dontje" <terry.don...@sun.com> wrote: > > >> WHAT: To make predefined handles extern to pointers instead of an >> address of an extern to a structure. >> >> WHY: To make OMPI more backwards compatible in regards to changes to >> structures that define predefined handles. >> >> WHERE: In the trunk. ompi/include/mpi.h.in and places in ompi that >> directly use the predefined handles. >> >> WHEN: 01/24/2009 >> >> TIMEOUT: 01/10/2009 >> >> >> ____________________ >> >> The point of this change is to improve the odds that an MPI application >> does not have to recompile when changes are made to the OMPI library. >> In this case specifically the predefined handles that use the structures >> for communicators, groups, ops, datatypes, error handlers, win, file, >> and info. >> >> An example of the changes for the communicator predefined handles can be >> found in the hg tmp workspace at >> ssh://www.open-mpi.org/~tdd/hg/predefcompat. >> >> Note, the one downfall that Jeff and I could think of by doing this is >> you potentially add one level of indirection but I believe that will be >> a small overhead and if you use one of the predefined handles >> repetitively (like in a loop) that the address will probably be stored >> in a register once and no additional over should be seen due to this change. >> _______________________________________________ >> devel mailing list >> de...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/devel >> > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel > _______________________________________________ devel mailing list de...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel
