Author: Dave Gomboc
Date: 11:32:26 06/22/99
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On June 22, 1999 at 13:17:35, Jay Scott wrote: > >On June 22, 1999 at 03:45:51, Dave Gomboc wrote: > >>Keep track of the computed score for a position separately from the backed-up >>score for a position. If they differ significantly, an important alternative >>was overlooked. > >You're suggesting the obvious algorithm, almost exactly what I suggested >some months ago. It predates "some months ago" by a long time. I am sure people thought of it at least 10 years ago. >This bit is not quite right. The scores might differ solely because of >the effective search horizon. For example, after 1. e4 e5 2. f4, suppose a >normal search evaluates 2... exf4 as +100 for black, or close. Backing up deep >values from the book might give the move an evaluation around 0--and yet >still identify 2... exf4 as the best move. There's a big score difference, >but it doesn't have anything to do with overlooking an alternative. The alternative overlooked can be later. Alternatively, the computation ended before it should have. It's a heuristic, nothing more. >The most powerful way seems to be this: > >0. Having backed up all scores below a node, >1. load these scores into the hash table, marking them as exact values >so that the current search won't try to look beyond them. (They're >based on a deeper search, so this search won't be able to see anything new.) >2. Search from the node. >3. If the best move is not already in the book, the program has found >a novelty. This must be corrected immediately: add it to the book. Overspecified, but it will work fine. >A more intensive novelty-search would find all moves within, say, >half a pawn of the best move. Just use the "Next Best" feature until >you've got 'em all. For the Kasparov effect, repeat the novelty search >on the novelties until you have a whole subtree of analysis ready for >your next opponent. The new scores float up the tree and may change >the best move at the original node--the ideal is to discover that the >novelty that seemed at first to be second-best is actually quite strong. Even the second-best ones are fine. As a rule, you only get one game with them before they're not novelties anymore. As long as it gives the opponent something to think about and a chance to go wrong, you're ahead. >Offline book learning is *way* more powerful than the online book >learning that chess programs use now. Here's a paper about a simple >method (used in an othello program): > >"Toward opening book learning" by Michael Buro >compressed postscript, five pages >http://www.neci.nj.nec.com/homepages/mic/ps/book.ps.gz I've read it. > Jay Dave
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