Author: Dann Corbit
Date: 18:51:01 10/09/01
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On October 09, 2001 at 21:26:54, Slater Wold wrote: [snip] >You would think. But it looks like TB's *might* be hindering the discovery of a >quicker mate. For sure. When there are a lot of pieces on the board, chess programs will simplify by trying direct exchanges. They will even toss a queen for *no reason* except that it knows how to solve without the queen. Imagine that you have kqqqkr, and on the board we have kqqqqqKR. The chess engine will very likely toss out two queens, if it sees a sure mate using the kqqqkr tablebase. And why is it so hard to shake out of it? Because of alpha beta. One thing about Alpha-beta, it knows a bird in the hand is worth two in the bush. If I have a mate in 35, and another path might put me up 3 queens, it won't even consider the other path -- it will exit right away because it sees: If I chose door #1, I get a checkmate in 35 (value 32767-5) If I choose door #2, I get a 3 queen advantage (value +30) Therefore, choose door #1. Do not continue to search until the next iteration. Also, if I have an advantage of a sure checkmate, any other choice will look like a massive loser if it is not a shorter checkmate. Now, there will be 3 queen advantages that lose (pretty rare of course). Tablebase wins can be clear beyond hideous all the way to commical. But they will be absolutely certain to win, and so the goal is achieved.
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