Author: Vincent Diepeveen
Date: 10:46:04 10/13/00
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On October 13, 2000 at 11:50:27, Kim Roper Jensen wrote: >No text it's pretending you know in advance what is the best move and just let the program figure out the tactics. it's fast and of course my first line is a rude outline of what it is, but it's definitely no compare to a leaf evaluation. So the 2 things against each other: - prescan heuristics/ piece square tables: fill a table BEFORE you search and apply there the knowledge so for example for each piece at each square and in your makemove only add the score from the tables and do nothing in your leafs (don't see why one would need a qsearch in fact for such programs a 'guess' function should be plenty enough). No evaluation needed. Even passers you can easily do incremental, no problem. - leaf eval: you can sure use the makemove to build up datastructures, but the evaluation is NOT dependant upon the moves made, but only upon the position and you go scan the board position in each leaf for chess knowledge. So the big difference is for example when exchanging queen: chess tiger used (don't know whether it's still a preprocessor) to be happy before queen exchange, then after queen exchange it's suddenly very unhappy. Old fritz versions except the latest 6a,6b etcetera were also preprocessors. Of course many programmers figured out that using a preprocessor only is very hard to play chess, so usually a few big scores they do in eval like passed pawns. Many old programs simply had no king safety at all. Nimzo is a classical case of preprocessing too. if you checkout its book you'll see it hardly plays openings with very tough pawnstructures without having all tough lines in book, as otherwise the preprocessor makes big mistakes as it doesn't see the position change in the root of course. Now where is the big advantage of preprocessors apart that you can do it faster, why have they been so pretty successfull in the past? I think very important reason is that it's also very easy to debug a preprocessor when comparing that with a leaf evaluation. Greetings, Vincent
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