Author: Robert Hyatt
Date: 18:36:56 08/14/05
Go up one level in this thread
On August 14, 2005 at 20:59:33, Uri Blass wrote: >On August 14, 2005 at 20:12:37, Eugene Nalimov wrote: > >>On August 14, 2005 at 20:08:21, Uri Blass wrote: >> >>>On August 14, 2005 at 18:01:28, Robert Hyatt wrote: >>> >>>>On August 14, 2005 at 17:00:02, Bernhard Bauer wrote: >>>> >>>>>On August 14, 2005 at 16:47:43, Darrel Briley wrote: >>>>> >>>>>>On August 14, 2005 at 15:22:43, Graham Banks wrote: >>>>>> >>>>>>>Best wishes for the remaining games. It would be really good for this to be the >>>>>>>best Crafty ever! Fingers and toes crossed! >>>>>>> >>>>>>>Graham. >>>>>> >>>>>>1.5 with two blacks vs. Shredder and Junior. Impressive indeed. >>>>>>Congratulations Bob! >>>>>> >>>>>> DB >>>>> >>>>>As Bob has pointed out earlier this is pure luck. >>>>>Crafty has serios tactical weaknesses as all the >>>>>computer chess specialists know. Crafty is not even commercial, >>>>>so how can this be explainded in any other way, but luck? >>>>>Perhaps Bob has found a very old version and is running this now, 6.4? >>>>> >>>>>Anyway congratulations and >>>>>Kind regards >>>>>Bernhard >>>> >>>> >>>>I'd bet that those "serious tactical weaknesses" are not to be found on this >>>>hardware, at least until someone is searching far faster than I am... >>> >>>Tactical weaknesses can be found also in software. >>> >>>> >>>>Crafty's "serious tactical weaknesses" are more urban legend than fact... >>> >>>Comparing Crafty with fruit Crafty does not do checks in the first ply of the >>>qsearch when fruit does it and Crafty does not use history based pruning when >>>fruit does it. >>> >>>I think that these are relative weaknesses and using the ideas of fruit may help >>>Crafty to be better in tactics. >> >>Those are not "ideas of fruit". Both are mentioned in the 1977 computer chess >>book written by KAISSA authors. >> >>Thanks, >>Eugene > >You may be right but fruit proves that they can work practically in chess >programs and Fabien showed the relevant source and as far as I know Bob never >tried checks only in the first ply of the qsearch. Look at the comments in main.c... You might be surprised to see that I did checks in the q-search until just prior to Jakarta, which was version 10.x I think.. So this was in Crafty in 1995. And removed in 1996 before the WMCCC that year... I tried them in the first ply only, the first two plies (that is the so-called extension search mentioned first below) and so forth... * 2.5 first check extensions added. in the extension search (stage * * between full-width and captures-only, up to two checking moves * * can be included, if there are checks in the full-width part of * * the search. if only one check occurs in the full-width, then * * only one check will be included in the extension phase of the * * selective search. * * 4.0 evaluation units changed to "millipawns" where a pawn is now * * 1000 rather than the prior 100 units. this provides more * * "resolution" in the evaluation and will let Crafty have large * * positional bonuses for significant things, without having the * * small positional advantages add up and cause problems. V3.8 * * exhibited a propensity to "sac the exchange" frequently because * * of this. it is hoped that this is a thing of the past now. * * also, the "one legal reply to check" algorithm is now being used. * * in short, if one side has only one legal reply to a checking move * * then the other side is free to check again on the next ply. this * * only applies in the "extension" search, and allows some checks * * that extend() would normally not follow. * * 5.5 checks are now back in the quiescence search. Crafty now stores * * a negative "draft" in the transposition table rather than forcing * * any depth < 0 to be zero. the null-move search now searches the * * null-move to depth-1 (R=1) rather than depth-2 (R=2) which seemed * * to cause some tactical oversights in the search. * * 5.6 improved move ordering by using the old "killer move" idea. an * * additional advantage is that the killers can be tried before * * generating any moves (after the captures.) quiescence now only * * includes "safe" checks (using Swap() to determine if it is a safe * * checking move. * * 8.12 fixed minor bugs in quiescence checks, which let Crafty include * * more checks than intended (default quiescence_checks=2, but the * * comparison was <= before including a check, which made it include * * three. Additionally, a hashed check was *always* tried, even if * * quiescence_checks had already been satisfied. pawn scoring also * * had a bug, in that there was a "crack" between opening and middle * * game, where Crafty would conclude that it was in an endgame, and * * adjust the pawn advance scores accordingly, sometimes causing an * * odd a4/a5/etc move "out of the blue." minor bug in next_capture * * was pruning even exchanges very early in quiescence search. that * * has now been removed, so only losing exchanges are pruned. * * 9.5 "vestigial code" (left over from who-knows-when) rmoved from * * Evaluate(). this code used an undefined variable when there was * * no bishop or knight left on the board, and could add in a penalty * * on random occasions. quiescence checks removed completely to see * * how this works, since checks extend the normal search significant * * amounts in any case. QuiesceFull() removed and merged into * * Quiesce() which is faster and smaller. first impression: faster, * * simpler, better. the benefit of no quiescence checks is that the * * exhaustive search goes deeper to find positional gains, rather * * than following checks excessively. No noticable loss in tactical * * strength (so far). * > >There are other public chess programs that use these ideas like Glaurung and I >also use these ideas in the last years in Movei but the motivation to try an >idea should be bigger if it is clear that it works for stronger chess programs >and Fruit is stronger than Glaurung so I mentioned fruit. > >Uri
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