Author: Robert Hyatt
Date: 19:12:45 07/06/99
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On July 06, 1999 at 16:34:06, Andrew Slough wrote: >On July 06, 1999 at 15:38:49, Zachariah Amela wrote: > >>Hello all. I am most interested in this type of system configuration, >>especially in the realm of computer chess programming. Any information would be >> most gratefully accepted. >> >>My question are: >> >>How exactly does this work? How would one code for such a system? > >You're probably thinking of Symetrical Multi-Processing (SMP) systems. They work >by having a number of processors all talking to a single shared memory. >Processors have to know about this because they have on chip caches and chips >must support `bus-snooping' to enable SMP. Cheaper chips like K6 don't support >bus-snooping because the market for SMP computers is small (~1% ??). > >One codes for SMP systems by having processes communicate via the shared memory, >which means communication is `zero' cost. For a chess program, at some point in >your search tree you will have one processor examine one sucessor while another >examines another. Because alpha-beta means that sometimes (often) you only need >to examine one sucessor at a node parallel alpha-beta algorithms aren't 100% >efficient - I think Bob Hyatt mentioned a typical 3.6 speedup with 4 processors >with crafty. > >> >>Who produces multiprocessor systems currenlty? I know Sun does as does Oracle, >>but anyone in the x86 universe? > >Lots of random manufacturers produce 2-way and 4-way Intel based systems, >although I think there is one company who do an 8-way machine using some >hardware hack. >Appart from Sun, you might look at those nice Alpha machines - I think I've seen >16-way Alpha systems. I don't think the Cray T3 machines with 128 processors is >SMP (is it?) correct. It is a NUMA machine as are several others. Much more complex to use for chess due to memory considerations. > >> >>What operating systems support these systems? WindowsNT? Linux? MacOS? >>SunOS? > >NT/2000 - Yes >Win95/97/3.11 - No >Linux - Yes >MacOs - No >SunOs/Solaris - Yes > >> >>What is Beowulf? >> > >Beowulf is a way of parallel processing with clusters of workstation type >machines, typically linked using Ethernet. The problem with using Beowulf class >machines for chess is that parallel Alpha-Beta works best when the work is split >between processors near the bottom of the tree. Because the communication of >Ethernet is orders of magnitude slower than shared-memory, a chess program to >utilise a Beowulf class machine would have to split the work higher up the tree, >which means the algorithm would be less scalable. > >On the other hand you can have thousands of processors on a Beowulf class >machine. > >>Where could one purchase such a system? Better question; how could somone make >>his/her customer machine in this fashion? > >I don't know of any commercial or free programs utilising Beowulf class >machines, though there are some academic research programs. For an SMP based >machine you could just but an off the shelf quad-xeon machine and then run an >appropriate program on it... > >>What chess programs utilize this system? KnightCap? GNU? >> > >Crafty. >I think people were also talking about Fritz supporting SMP now, but I know >nothing about that. > >> >>Thank you very much! > >Andy
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