Author: James T. Walker
Date: 17:10:09 12/01/01
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On December 01, 2001 at 18:47:10, Russell Reagan wrote: >On December 01, 2001 at 16:35:31, Mike S. wrote: > >>After reading the Gandalf-GT 2 match discussion below (partially about problems >>recognising that RN-R, RB-R are usually draws), I'd like to ask what you think >>is the best recommendable (sub-)set of the table bases for practise including >>engine matches. >> >>I'm aware most people will say "use all 5 men tbs", but large experiments have >>been made showing that the slowdown effect and other effects from using the tbs, >>often result in *worse* performances in practical positions, than without the >>tbs. Misjudgement of continuations which keep the game out of tbs material, is >>one of these effects, which i.e. can make the win unecessarily easy for the >>opponent (which may - without tbs - fail to win if the best defense in played). >> >>I use the complete 3- and 4 piece-tables *plus* krnkr, krbkr, because these are >>very important draws. These two should not create an "incomplete" problem >>because they do not contain pawns. >> >>What do you think? >> >>Regards, >>M.Scheidl > >I have never understood why the advantages of using tablebases are outweighed by >the slowdown it causes. Here's my thinking; maybe someone can point out my >error. As I see it, if you have the complete n-man tablebases and their >subsets, then you can just keep track of how many pieces are remaining on the >board and if a position has n pieces remaining or fewer, then you play whatever >move the tablebase says, since that is the best line. I don't see how this >slows down anything, unless you're talking about incorporating probing the >tablebases into your search and evaluation of many positions. I hope someone >will explain this to me, because I've never implemented tablebases into my own >program and I plan to eventually, so I'm sure this will be something I'll need >to know eventually. > >Russell Most all programs are probing the tablebases at the leafs. This slows some down to about half the normal K/nps. Some like Shredder slow down to 10% of normal (In some positions) but the ply depth is greater because of the information obtained from the tablebases. By the way, I had a position today where one program with tablebases had one queen and announced mate on itself. The other program had two queens but without tablebases only managed a draw. Jim
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