Author: Bruce Moreland
Date: 14:44:38 06/02/01
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On June 02, 2001 at 13:58:17, Gian-Carlo Pascutto wrote: >>>>>>>>>>>>>>> >You wouldn't learn anything anyway. There aren't any secrets in it, other >than that I've been a little vague about describing how I implement singular >extension, but it's unclear that singular extension makes the program any >stronger. >>>>>>>>>>>>>>> > >Ferret actually uses singular extensions! > >Yeeaargh! Bruce, I'm terribly curious now. Tells us all the details :) > >-- >GCP I do a test to see if there is apparently only one move that doesn't suck. I do a reduced depth search. If the first few don't drive the score to something close to alpha, I leave, because I assume this is a fail-low node. If one of them drives the score pretty close to alpha, I check the rest to see if there are any more that do this. If there's only one move that looks decent, I call it singular and extend it a ply. This doesn't work in the endgame, but in the middlegame I found it improved solution times in the ECM suite dramatically, while costing a ply in the general case. This extension made my search pretty unstable so I had to do some of the hash table stuff mentioned in the DT article on singular extension published in the ICCAJ some years ago. When I ran two versions against each other, one with this extension stuff and one without it, it seemed to score almost exactly 50%. I left it in, for fun. The version that played in the WCCC 1999 used this. Don Beal came around collecting program information and I told him then, so it may have already been published in an ICCAJ. bruce
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