Author: Enrique Irazoqui
Date: 12:14:54 06/21/00
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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. Enrique > Christophe
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