Author: Vincent Diepeveen
Date: 06:26:31 09/03/03
Go up one level in this thread
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? >>>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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