Author: Uri Blass
Date: 06:58:19 09/27/00
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On September 27, 2000 at 09:02:35, Dieter Buerssner wrote: >On September 27, 2000 at 05:53:59, Uri Blass wrote: > >>On September 27, 2000 at 04:21:52, Dieter Buerssner wrote: >> >>>On September 26, 2000 at 16:51:33, Uri Blass wrote: >>> >>>>[D]3r3k/p7/1p6/2p2Q1p/2P1R3/2P5/P2KP3/6q1 w - - 0 1 >>>> >>>>Hiarcs played Kc2 and had to resign some moves later because the queen cannot be >>>>saved[the game continued Kc2 Qd1+ Kb2 Rd2+ Ka3 Qc1+ Ka4 b5+ cxb5 Qc2+ Ka5 Qxc3+ >>>>and white resigned because of the line Ka6 Rd6+ Kb7 Qg7+ Kb8(forced because Kc8 >>>>is leading to mate) Rd8+]. >>>> >>>>How much time do programs need to avoid this tactical error?(some program like >>>>hiarcs can play Rd4 after a short time but later change their mind to Kc2 so the >>>>right test is to give them at least some minutes) >>> >>>Interesting position. I think, it is not unlikely for many engines to switch >>>moves here. It needs some relatively deep search to see that the queen is lost. >>>Before this, Yace sees tactical strong lines after Kc2, but in between, at just >>>one depth, they seem to be refuted. >>> >>>Yace needs 64 seconds on AMD K6-2 475 MHz, 30MB hash. >>>[...] >>> 8756 0.131 -1.43 4t : Re4d4 Rd8xd4+ c3xd4 Qg1xd4+ Kd2e1 Qd4c3+ Ke1f2 >>> Qc3xc4 Qf5xh5+ Kh8g8 [-100] >>>[stays with Rd4 until] >>> 3464157 16.90 -0.66 10t : Re4d4 Rd8xd4+ c3xd4 Qg1xd4+ Kd2e1 Qd4h4+ Ke1f1 >>> Qh4xc4 Qf5xh5+ Kh8g8 Qh5e8+ Kg8g7 Qe8e5+ Kg7g6 >>> Qe5d6+ Kg6f5 Qd6d7+ Kf5e5 Qd7xa7 Qc4c1+ Kf1f2 >>> b6b5 [0] >>>[...] >>> 9973064 53.77 -0.36 10t : Kd2c2 Qg1d1+ Kc2b2 Rd8d2+ Kb2a3 Qd1c1+ Ka3a4 >>> b6b5+ c4xb5 Qc1c2+ Ka4a5 Qc2xc3+ Ka5a6 Rd2d6+ >>> Ka6b7 Qc3g7+ Kb7c8 Qg7g8+ Kc8b7 Rd6b6+ Kb7c7H >>> Qg8b8+H Kc7d7H Rb6d6+H Kd7e7H <HT> [0] >> >>I do not understand the score of -0.36 >>When I look in the final position of the pv even without searching deeper I >>evaluate it as a very big advantage for black. > >I agree, that this is no good evaluation. But it may not be as bad as it looks. > >>Reasons: >>1)The white king is in a very bad square and I am afraid from mate even before >>seeing it by search(it is a problem when the sides have queen and rook that is >>often enough to mate). > >But almost the same is true for the black king. With white to move, this is a >mate in 3. But of course ... > >>2)black is the attacker(it is black to move and black is not in check) >>I define the attacker as the side to move unless the side to move is in check. > >when the eval takes this into account, things are different. I hope, that the >search or search extensions would solve this problem. This may not be optimal >and I will think about the concept of side to move for this sort of eval terms. >Nevertheless, if I calculate extensions correctly, one ply deeper, the mate in >this line would be seen. > >>It seems to me that a better piece square table with big positional scores can >>help to have a better evaluation. > >Don't see this here. You want to punish the advanced king very much? > >>I do not unsderstand the reason that a lot of programs evaluate the final >>position of the pv as almost equal. >> >>Here is the final position of the pv >> >>[D]1q5k/p3K3/3r4/1Pp2Q1p/4R3/8/P3P3/8 b - - 0 1 >> >>evaluation of programs at depth 1: >>CometB20 1.61: pawns for black > >This really is interesting. Perhaps Ulrich Türke can tell, if he looks at the >side to move for king safty. > >>This kind of evaluations(except Comet) make me wonder if programmers think >>before writing the piece square tables because I expect more than one pawn bonus >>for king safety problems in this case and if you do not consider king safety >>then I also see positional advantage for black because black has 2 passed pawns >>when white has only one. > >How much is one passed pawn (not connected) worth in an open position with >queens on board, where there are allways threats for perpetual checks? > >>Are programmers afraid to have big bonuses of more than 1 pawn in the piece >>square tables? > >Where would you put bonuses of more than one pawn in piece square tables >(besides perhaps pawns on rank 7)? I admit that I cannot see cases of bonuses of more than one pawn(except pawn on the 7th rank) but I think that there are cases of panalty of more than one pawn. White knight at the corner a8 or h8 is often trapped in a few moves(I think that panelty of one pawn is logical in this case unless you have trapped piece code that tell you that the knight has no safe squares to go). I admit that king safety can be evaluated by other means and not by piece square tables but it is clear for me that usually white is in trouble when the white king is in bad squares like e7 and black is the attacker and the simplest solution seems to be to change the piece square table. It is possible to see that white has no friendly pawns near the king(in the case of the relevant position the same is for both sides so the side to move has a big advantage). If programs do not evaluate side to move then it seems to be better to evaluate positions when the white king is in squares like e7 as bad for white because most of these positions are result of attack of black and in logical lines black is going to be the attacker most of the time. Uri
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