Author: Aivaras Juzvikas
Date: 10:30:53 04/05/04
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On April 05, 2004 at 07:10:46, Vasik Rajlich wrote: >On April 04, 2004 at 11:13:18, Aivaras Juzvikas wrote: > >>On April 04, 2004 at 11:09:05, Vasik Rajlich wrote: >> >>>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 >> >>my engine is brand new and instead of many features it has many bugs -> the only >>extention i have now is this check (evasion i guess) extention. so meybe instead >>of restricting this extention i should add pawn on 7th rank extention and see >>how it does. what else is there in endgames to deal with besides mates and >>promotions?is there any other must-have extention i am missing? > >I guess that pawn push extensions are pretty standard. Aside from that, everyone >has their own little tricks. > >For example, in endgames, I reduce moves which capture an advanced passed pawn, >and I reduce promotions. > >I'm not 100% sure that it's a good idea, though. It's very difficult to get good >feedback on obscure situations, because any test you devise could be biased in >some way. > >Cheers, >Vas thnx for your help, i will test such extention sometime. ps. i guess you mean extention :)
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