Author: Robert Hyatt
Date: 09:00:58 09/03/03
Go up one level in this thread
On September 03, 2003 at 09:26:31, Vincent Diepeveen wrote: >On September 02, 2003 at 18:37:05, Jeremiah Penery wrote: > >>On September 02, 2003 at 07:15:55, Mridul Muralidharan wrote: >> >>> >>><snip> >>>On September 01, 2003 at 09:39:55, Jeremiah Penery wrote: >>> >>>> >>>>Any large (multi-node) SMP machine will have the same problem as NUMA with >>>>respect to inter-node latency. SMP doesn't magically make node-to-node >>>>communication any faster. >>> >>>Pardon my saying so , but it looks like you have very little idea about SMP and >>>NUMA. >> >>If I didn't have some idea what I was talking about, I wouldn't be talking, >>unlike a lot of people in these discussions. >> >>> Refer to cray architecture , an opteron 8 way box architecture , and some >>>IBM supercomp cc-NUMA based system architecture docs for more info. I'm not >> >>Those machines are designed and built for *completely* different purposes. You >>might as well compare the documentation for a P4 to that of an UltraSPARC, for >>all the good it would do you. >> >>>refering to just theoretical differences , or _only_ architecture differences - >>>but as a programmer - what details that need to be taken care of while writing >>>apps for such a system. >> >>And those details would be what, other than the aforementioned theoretical or >>architectural differences? >> >>>>But in reality, almost nobody uses a machine that big, especially for chess. >>> >>>The question was - can it be done , is it just a bunch of tweaks - not do you >>>have a system. >>>Answer : Yes it cn be done , needs lots of rewrite - not just "tweaks". >> >>Not really. Bob said he already completed the changes, and it didn't really >>involve much. Only instead of forking processes he had to manually start >>processes on each processor. That really doesn't take much work. > >But that's of course not true. > >Why are you believing this nonsense? Would you like a name at Compaq? They sent me an alpha, and a NDA copy of their UPC compiler to do this work. I didn't publish anything due to the NDA of course, but that has lapsed and the compiler is now commercially available. Why do _you_ write this nonsense??? > >>>>For any but the most extremely scalable architectures, there is significant >>>>diminishing returns when adding processors for chess playing. I'd say that a >>>>very scalable 8-way SMP or NUMA (Opteron) machine will not be very much slower >>>>than even a 64-way Alpha/Itanium/xxx machine for chess. >>> >>>If badly programmed , then yes not much difference between a 8 proc box and a 64 >>>proc box (actually it can be lower performing!). >>>Which is exactly my point , you need to design a program specifically to run on >>>such a system - not expect something that works on a 2 or 4 proc system and >>>expect it to work for a 64 proc system ! >> >>The Alpha-Beta algorithm used for chess is a serial algorithm. There's no >>getting around that. The more processors you use, the less efficiency you will >>get, unless you use something else than Alpha-Beta. >> >>No matter how much you want to rewrite and "tweak" for a NUMA machine (or any >>kind of machine, for that matter), adding more and more processors is simply >>going to stop being beneficial at some point.
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