Author: Enrique Irazoqui
Date: 02:41:52 06/22/00
Go up one level in this thread
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. 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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