Author: Uri Blass
Date: 00:15:07 09/03/04
Go up one level in this thread
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. I see no point for it. I am sure that I can solve Qxf4 even in less nodes than tord by adding some stupid extensions but this is not the target and the target is to play better. I discovered that I can solve more positions in the ecmgcp if I reduce my evaluation based pruning but again it is not the target and the main question is if I can play better with it. 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. > >Alpha=-1182 Beta=-682 Maxdepth=9999999 MaxTime=100000 > 1/13 g2f1 0.01 -953 945 g2f1 f4d5 > 2/13 g2f1 0.01 -953 1535 g2f1 f4d5 c1g5 > 3/15 g2f1 0.02 -953 5010 g2f1 f4d5 c1g5 d5f6 > 4/23 g2f1 0.09 -953 21387 g2f1 f4d5 b3d5 c6d5 c1c7 d6c7 f1g1 > 5/25 g2f1 0.65 -953 179404 g2f1 b5b4 b3a4 f4d5 f6g5 d5e7 > 6/44 g2f1 3.15 -953 728459 g2f1 b5b4 b3a4 f4d5 f6g5 d5e7 > 7/48> g2f1 64.75 -703 15048349 g2f1 e8c8 f1g1 c8e8 c1b1 f4e2 g1g2 e2d4 > 7/48 c1f4 98.86 5113 24322991 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 > 8/48< c1f4 98.88 4863 24327933 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 > 8/48 c1f4 108.60 4863 26455348 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 > 9/48> c1f4 159.87 5113 38207334 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 > >I know my PV is screwy and wonder why Bxf4 isn't played next. Anyone >know why? To me, Qxf4 followed by Bxf4 and then rook taking along the >H file looks like the natural PV. I wonder if that is another nasty >bug lurking. No After Qxf4 Bxf4 lead to a sinple mate so black has no choice but not to capture. If you extend Bxf4 then it is clear than not playing Bxf4 is not extended so even if both Bxf4 and the alternative are equal you are going to see that Bxf4 is losing by mate earlier because of extensions. I am surprised there can be so many remaining considering >a fairly decent run-of-the-mill score on WAC 1-300. The set seems to >have shortcomings. Good for a first year's development effort though. > >I am not able to speed 141 up yet with Moreland's Mate Threat Null extension If you are not able to see it at smaller ply with mate threat extension then you must have a bug and I suspect that you have return beta or return alpha and not return val in your search(otherwise even without checks in the qsearch you could see Qxf4 Bxf4 Rxh5 null Rh8#). You should check what is the first iteration that Qxf4 Bxf4 Rxh5 null is searched with remaining depth 1 after null to see if your program detect mate threat to extend it. nor >Botvinnik-Markoff's extension, but hopefully those will help, though they >haven't so far. Nor did using checking moves in the quiescence search. >None of those three has improved the time of the above, for me. I haven't >tried leaving out all check evasion moves in the main search and quiescence >search which speeds up the program tons but makes tactical solution rates >suffer. > >New recapture tested just slightly less than 1% worse in score on Win-at-Chess >for me but is solid enough to be okay to keep as a permanent setting. I think that you are wrong. The basic rule should be that an extension is probably bad if it does not improve results in test suites. I do not say the same for pruning and I believe that there is a bigger chance that pruning is good inspite of reducing the result in test suites. Test suites usually encourage not even recaptures and it does not mean that it is good to extend them in games. Uri
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