Author: Robert Hyatt
Date: 10:10:24 09/12/01
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On September 11, 2001 at 22:49:49, Vincent Diepeveen wrote: >On September 10, 2001 at 18:13:51, Dan Andersson wrote: > >>I know of at least one search method that would fit perfectly on this kind of >>machine. I recently had the pleasure to be able to run an old Othello program of >>mine on a brand new NUMA machine. Implementing a published algorithm. I was >>surprised to find a near linear function speedup to the number of processors >>close to one to one, up to all sixtyfour available. There was of course a small >>slowdown at each node but all in all it was a profitable tradeoff. >> >>MvH Dan Andersson > >Unless that 'lineair speedup' is like 0.01 or something so very small >i don't believe a word of it for computerchess. > >We search that deeply nowadays that getting a good speedup at a cluster >is nearly impossible. I do not know of course how important hashtable >is for othello and i do not know the quality of other programs you compare >it with. > >AFAIK othello was nearly solved, is it? > >How would you distribute hashtable on a machine with such a slow communication >speed like this machine? 1. I don't believe that reasonable speedup is impossible on a cluster. I don't believe a cluster can do as well as an SMP machine, however. 2. Distributed hashing has been shown to work. It makes the program design a bit more complex, because when you need to fire off the hash probe as soon as possible, and you need to search as though there will be no match. But if a remote machine returns a hash entry a bit later (1/2 node later or more) then you can _still_ use the information belatedly and take whatever action is needed. Since a typical middlegame gets < 20% hash hits, this means that in more than 80% of all nodes you have no problem anyway. 3. There have been successful cluster chess machines. Phoenix is one. It wasn't as good as an SMP implementation, but it was definitely better than using a single CPU.
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