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" 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
Re: [OMPI devel] RFC: make predefined handles extern to pointers
Terry Dontje wrote: 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? Rich, I retract the above. HPCC and IMB probably doesn't use the predefines that much. One might be able to just do a lot of MPI_Comm_rank calls but then you run into the caching problems you mention above. Though I wonder if we do enough runs and compare the first call if that might be enough. --td --td On 12/16/08 10:41 AM, "Terry D. Dontje" 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
Re: [OMPI devel] RFC: make predefined handles extern to pointers
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 To: Open MPI Developers 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" 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
Re: [OMPI devel] RFC: make predefined handles extern to pointers
On Dec 16, 2008, at 7:41 AM, Terry Dontje wrote: 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 . For those who don't have ssh accounts: http://www.open-mpi.org/hg/hgwebdir.cgi/tdd/predefcompat/ -- Jeff Squyres Cisco Systems
