Author: Ed Schröder
Date: 08:20:44 06/22/00
Go up one level in this thread
On June 22, 2000 at 07:26:29, Ed Schröder wrote: >On June 22, 2000 at 05:41:52, Enrique Irazoqui wrote: > >>On June 22, 2000 at 00:43:00, Ed Schröder wrote: >> >>>On June 21, 2000 at 15:14:54, Enrique Irazoqui wrote: >>> >>>>On June 21, 2000 at 13:53:13, Christophe Theron wrote: >>>> >>>>>On June 21, 2000 at 08:30:59, Enrique Irazoqui wrote: >>>>> >>>>>>[D]1r6/1pb1k1p1/4p2p/1p1p4/3Pp2P/1R2P1PB/1P2P1K1/8 b - - 0 1 >>>>>> >>>>>>Yesterday I looked at this position that reveals once again how much trouble >>>>>>programs have in recognizing the importance of blocked pieces. Some programs >>>>>>pick and drop 1...b4, but none of them realize that the blocked rook is out of >>>>>>the game until the search makes them see the consequences many hours later. The >>>>>>evaluation at the initial position or after 1...b4 2.Rxb4 b5 3.Rb3 b4 is almost >>>>>>the same. It takes 61 minutes for F6a and 335 minutes for Tiger to pick b4, and >>>>>>much, much longer to fail high. >>>>> >>>>> >>>>>Well, life is unfair. I do have something for this kind of positions in Tiger. >>>>>Normally Tiger is able to suspect that the rook is in trouble. >>>> >>>>Do you have to treat differently the cases of blocked rooks or blocked knights >>>>and bishops? So many times I hear programmers looking for patterns. Well, this >>>>is one, isn't it? In the first position, the rook can't move or a pawn will take >>>>it. In the second and third, the bishop is statically trapped by a chain of >>>>pawns in a small corner of the board. Technical question from an illiterate: >>>>wouldn't it make sense to heavily penalize such positions? >>>> >>>>For instance, Junior 6a is the program that does best with the first position. >>>>It picks b4 in 51 seconds and sticks to it forever, but the difference between >>>>b4 and the next best is only 8/100 of a pawn after 4 hours. So it doesn't quite >>>>get it, and in the other 3 positions it fails. >>>> >>>>>However, for an unknown reason, it looks like it does not work in this here... >>>> >>>>Tiger doesn't get the other positions either (no program does). Pattern? >>>> >>>>>Sometimes I wonder if adding this kind of knowledge is worth the trouble, as >>>>>there are so many exceptions, and even cases where the knowledge is counter >>>>>productive, or is not triggered at the right time! >>>> >>>>These positions come from real games, one of them from a computer game, so I >>>>guess it must be productive to teach them this kind of things. I may be >>>>exaggerating, but looking at some human-computer games, like the ones lost by >>>>Fritz in the Dutch championship, it seems clear that blocking positions is an >>>>efficient anti-computer strategy. But how can a program recognize a general >>>>blockade if it's incapable of realizing that one piece is trapped? >>>> >>>>In my opinion, this also has to do with a more general issue of aesthetics, of >>>>programs being able to produce some sort of beauty other than announcing mate in >>>>128. >>> >>>I don't have much trapped piece code in Rebel. But 1..b4 is quickly found >>>with a score difference of 1/4 of a pawn in comparison with the previous >>>best move. I don't know why Rebel picks 1..b4 but in any case trapped piece >>>code isn't an issue here so there are other positional aspects valid for >>>this position too. >>> >>>Ed >> >>But at ply 16 Century 1.2 drops b4 in favor of h5 (+0.66), and then at ply 17 it >>picks again b4 (also +0.66), so the difference in evaluation between b4 and h5 >>is less than 1/100 of a pawn. > >I used the latest version. If I don't forget I will run the position >overnight and see if it does the same. Tried the position for a few hours. On ply 15 Rebel switches to 1..h5 and the score is going up to 0.90 and sticks to 1..h5 all the way to ply 18. From the main-line I understand that 1..h5 wins a pawn. But of course I agree that the 1..b4 approach is much more powerful than just a pawn. But a pawn is a pawn and is rewarded higher than the value of the trapped rook or whatever it is Rebel decides for 1..b4 in the early iterations. Ed >>Enrique >> >> >>>_____________________________________________________________ >>> >>>00:00:00 8.07 0.36 1..Kd6 2.Rxb5 e5 3.Rb3 Ba5 4.Bg4 >>> g5 5.hxg5 hxg5 (0) >>> >>>00:00:01 9.00 0.38 1..Kd6 2.Rxb5 e5 3.Bg4 b6 4.Rb3 >>> Rf8 5.Ra3 Bd8 (1) >>> >>>00:00:03 10.00 0.39 1..Kd6 2.Rxb5 e5 3.Bg4 b6 4.Rb3 >>> Rf8 5.Ra3 Bd8 6.Ra1 (2) >>> >>>00:00:05 10.16 0.39 1..b4 >>>00:00:06 10.16 0.56 1..b4 2.Rxb4 b5 3.Bg4 Bd6 4.Rb3 >>> b4 5.h5 Rf8 (5) >>> >>>00:00:07 11.00 0.58 1..b4 2.Rxb4 b5 3.g4 Bd6 4.Rb3 b4 >>> 5.g5 Rf8 6.gxh6 gxh6 7.Bg4 (6) >>> >>>00:00:18 12.00 0.61 1..b4 2.Rxb4 b5 3.g4 Bd6 4.Rb3 b4 >>> 5.g5 hxg5 6.hxg5 Rh8 7.g6 Kf6 (13) >>> >>>00:00:45 13.00 0.61 1..b4 2.Rxb4 b5 3.Bg4 Bd6 4.Rb3 >>> b4 5.h5 Kf6 (32) >>> >>>00:02:06 14.00 0.64 1..b4 2.Rxb4 b5 3.Bg4 Bd6 4.Rb3 >>>00:06:30 15.00 0.63 1..b4 2.Rxb4 b5 3.Kf2 Bd6 4.Rb3 >>> b4 5.Kg2 Ra8 6.Bg4 (237) >>> >>> >>> >>>>Enrique >>>> >>>>> Christophe
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