Author: Omid David
Date: 15:42:40 08/30/02
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On August 30, 2002 at 17:39:27, Gian-Carlo Pascutto wrote: >On August 30, 2002 at 17:37:25, Patrik wrote: > >>Difference is that Crafty used alpha instead of value when it re-searches. >>Is there any reason to use alpha instead of value? >>Using value which is greater than alpha seems to cause more cutoffs than using >>alpha. > >If you get a fail high on the first search and a fail low on the second (*), >you will lose your PV's. This does not happen if you do the research with >alpha. > >(*) If you think this can't happen, you haven't been doing chessprogramming >long enough. > >-- >GCP If you take a look at Aske Plaat's PhD thesis "Research Re: Search and Re-search" and his numerous other publications, you'll notice that on many occasions his results are not substanciated enough in practice. For example he conducts all his experiments (on 20 test positions, depth 8) in brute force fixed depth search, which is extinct nowadays (even in 1996, who didn't use a form of variable depth search?). Right on the other side, stands Ernst Heinz, which has published extensive *practical* research, working on different "read world"(!) issues (e.g. null-move pruning, futility pruning, etc). But Heinz's work was mostly applicable for chess only, while Plaat worked also on Checkers and Othello (something I don't plan to do!). P.S. Despite this little criticism on Plaat's thesis, I believe that it's still one of the best and most contributing theses published on computer chess.
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