Author: Robert Hyatt
Date: 18:29:43 11/10/02
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On November 10, 2002 at 21:15:07, Jim Bumgardner wrote: >Which of these strategies for "think on opponent's time" makes more sense? > >A) To only search the top-move from the principle variation. If >the opponent makes that move, continue searching, otherwise reset and >search again. This is the _only_ way to do it. I've explained this many times, but it is probably time to go it again... Suppose you predict your opponent's move correctly only 50% of the time. And it should be pointed out that this is a _low_ estimate from thousands of observed games (via log files). This means that 1/2 of the time, you will predict correctly and when your opponent moves, you have an instant response ready. 1/2 of the time you get to think for free. Suppose you choose to search the top three moves instead of just the first one. When your opponent has moved, you have spent 1/3 of the total time on each move. You save 1/3 of the time. And that is worse than saving 1/2. If you only search the top 2 moves, you will save 1/2 of the time, _if_ the move played is one of those two, but occasionally it won't. It is really simple to see why searching only the best move is the right idea. I could think of a few cases where I might vary this, such as where my target time is 3 minutes and my opponent searches for 12 minutes. Do I want to search one move for 12 minutes, or do I want to take a chance and use 1/2 of that time (say) to search for an alternative best move? Tough to say, and although I have tried such ideas many times, I have always come back to searching what I consider the best move only. And since 50% is a low prediction percentage, searching one move actually is even better than the above pessimistic analysis. > >B) To search all possible moves the opponent might make. When the opponent >moves, reset and search again (but faster, since the hash tables have been >seeded). see above why this is not so good... > >C) Some other strategy? For example, to use A) only if the top move is >'singular' (has a significantly better score). > >What strategy does your chess engine use? To date, I have been using "A", >but I am beginning to think that "B" or "C" might be better. > >- Jim
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