Author: Jeremiah Penery
Date: 15:37:05 09/02/03
Go up one level in this thread
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. >>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.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.