Author: Uri Blass
Date: 05:46:08 09/03/04
Go up one level in this thread
On September 03, 2004 at 07:08:48, Andrew Platt wrote: >On September 03, 2004 at 00:43:27, Stuart Cracraft wrote: > >>So today I find out that my recapture is bad. It must be. Bob said so. >> >>I take 1 minute to reimplement it to be "extend on 2nd capture on the same >>square in a row" because I heard someone else talking about that's the >>way they do it and got a surprise a minute after that. >> >>The result is that Qxf4 for Win-at-Chess comes into view >>in 98 seconds and holds after having been missed after seemingly >>endless runtime with the old bad recapture in or out. Of course >>it is nothing like the 13,000 nodes that Tord (was it?) solves >>141 in. Perhaps we should have a contest for who solves 141 in >>the fewest moves. He would surely win. It takes me 24 million. >>I admire a search that is so directed in so few nodes. Surely >>we pay homage to Berliner with it, eh? Retire in peace in Florida >>and then two category 4 storms hit. Unlucky fellow. > >Congrats but I seriously think there must be something strange if mate threat >extensions don't help. I don't have recapture extensions (yet) but the mate >threat brought it down from a 13 ply search to an 11 ply one. It's still way too >expensive because the tree is very large at that point and with the alpha-beta >window being wide open for the mate score it takes forever. > >Right now I'm focussing on why it doesn't get it sooner; after that I'll >implement re-capture extensions. > >I think that looking at checks in the quiescent search would have helped me a >little. When analyzing the trace files I see the null move dropping straight >into quiescent search with a mate (e.g. a null move after Qxf4 Bxf4 Rxh5 - null >- Rh8#). However, all it does is the stand pat evaluation which causes a beta >cutoff. > >It would be too expensive for me to really deal with checks in qsearch because I >don't want to have to generate the legal capture modes. All I do is bomb out of >it if I see the King being captured. However, it might not be too expensive to >generate the legal moves at the first ply of qsearch if we're in check to catch >these conditions. I might try that and see if it causes testsuites to slow down >much. > >Andy. You do not need to do it. If you extend every check by 1 ply in correct way there is 0 chance to get position when the king is in check in the first ply of the qsearch. Uri
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.