Author: Vasik Rajlich
Date: 08:09:05 04/04/04
Go up one level in this thread
On April 04, 2004 at 11:03:07, Vasik Rajlich wrote: >On April 04, 2004 at 10:55:38, Aivaras Juzvikas wrote: > >>On April 04, 2004 at 10:48:55, Vasik Rajlich wrote: >> >>>On April 03, 2004 at 06:29:13, Aivaras Juzvikas wrote: >>> >>>>On April 03, 2004 at 06:21:51, Vasik Rajlich wrote: >>>> >>>>>On April 03, 2004 at 04:02:57, Aivaras Juzvikas wrote: >>>>> >>>>>>i have got this problem here, check extention explodes in the endgame pawns + >>>>>>rook or queen, all these open files make it possible to check endlessly. how to >>>>>>restrict this? i added smth like this: if ply > depthtoreach + 4 then dont >>>>>>extend, where depthtoreach is the depth im searching to. but this is ofcourse >>>>>>not very good, because i still get those check extentions where its impossible >>>>>>to mate anyway. how did u solve this problem? an idea would be to store info >>>>>>into transposition table when not to extend, but how to find that out? >>>>> >>>>>Are you extending checks, check evasions, or both? >>>>> >>>>>The third option is quite appealing, but there are some issues. :-) >>>>> >>>>>Cheers, >>>>>Vas >>>> >>>>when side to move in in check i extend, so i guess it would be a check evasion >>> >>>So, in certain positions, you are extending every other move. It's true that in >>>these positions this will severely hurt your nominal depth, but if you test with >>>the extension and without it you should see a clear benefit. I don't remember >>>any claims to the contrary. >>> >>>Vas >> >>well here is a claim to the contrary: in endgame rook+pawns vs rook+pawns >>instead of dealing with passed pawns the engine keeps on extending checks >>endlessly thus overall looking very few ply ahead and the result is a loss of a >>rook due to pawn promotion. usually (w/o endless check extention stuff) i reach >>15-17 ply depth in endgame, with check ext. stuff i get 7-8ply, and again only >>when slider like rook or queen is present which can keep on checking no matter >>what you do. dont u restrict your extentions somehow? please share with me how >>to do this > >Aha. That's a good point, maybe it's worth testing. > >My program Rybka always extends every check one full ply. > >However, maybe it should be a bit less in the endgame, and perhaps even a bit >more in the middlegame. (This I did experiment with.) > >This is worth some tests. > >It would be interesting if you posted some numbers. (You can always find some >good cases, and some bad cases.) > >Vas One more thought about this: in the endgame, it may be a question of calibrating against pawn push extensions. (Ie rather than decrease the check extension, increase the pawn push extension.) A few months ago I played around with some hyper-aggressive passed pawn extensions, up to 3 plies extra for any pawn which reaches the seventh rank in an endgame. It worked nicely on some tactical problems, but there were also some exploding searches. Cheers, Vas
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