Author: Steve Timson
Date: 11:59:10 01/24/02
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I am not sure really :). The singular extensions I use are far simpler than a classical deep blue style implementation. What I do was inspired by comments Bruce made at CCT3 - basically, if a (significantly) reduced depth search of the moves at a node reveal that only one move produces a score near alpha (the rest are all worse), then extend it. Parameters to play with include - how much to reduce depth for the reduced depth search, how much better must one move score than the others to be considered singular, what part of the tree and what part of the game to enable the code (e.g. I have had better luck restricting the extensions to fairly near-root nodes), how it interacts with other extensions (what extensions should be enabled at the same time, and what extensions should be enabled when it is off - e.g. I don't do recap extensions when it is on, but do in parts of the tree where it is off), etc. To me it has seemed worth it, but the cost is pretty steep. In the results posted below you can see it roughly doubled the number of nodes needed to hit ply 10 - it can be much worse too. I do some pretty significant forward pruning, which helps keep it in check some - I am not sure I'd want to do SE without it. On test suites it helps me quite a bit, I haven't run with it off lately, but if I recall right, enabling it gained me roughly 40 ecm solutions at 20 seconds per move (chester currently scores 661 at 20secs). It also seems to have helped a lot playing weaker humans on ICC - you know the type of people that play 50 5 0 games in a row, looking to get that one draw. More frequently now some tactical shot is discovered. Anyway, it seems this way. It seems to harm performance in fast games vs comps though. - Steve On January 24, 2002 at 11:43:01, Will Singleton wrote: >On January 24, 2002 at 05:49:44, Steve Timson wrote: > >>Chester finds it in 2.17 seconds on my athlon 1200. >> > >Well, pretty darn impressive. Where's the best info on singular extensions? > >Will
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