Author: Andrew Slough
Date: 13:34:06 07/06/99
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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?) > >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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