Author: Robert Hyatt
Date: 07:21:51 01/26/00
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On January 26, 2000 at 04:28:02, Amir Ban wrote: >On January 26, 2000 at 00:42:20, Robert Hyatt wrote: > >> >>maybe or maybe not. In 1970 we were _all_ selective searchers. Chess 4.x >>changed that in 1975. By 1980 nobody that was winning was selective. Then >>we went the other way with null-move and so forth. Maybe the right way is >>not risky forward pruning, when you have enough horsepower. Which sounds >>_exactly_ like what Slate/Atkin said in 1975 when you think about it. :) >> > >The early selective searchers did pruning based on very superficial indicators, >mainly move ordering through static evaluation. That was a stupid thing to do, >and it is wrong at any level. Pruning, when based on more reliable indicators, >is a good thing at any level. > >Amir Some did, but not all. Mine was searched based. I searched a tree with a very good tactical analyzer guiding the search, but it was incapable of detecting threats against itself, only finding moves with threats against the other side. I did a search, then looked at the results as they were backed up with a "causality detector" to let the good threat detector find the threats and execute them, then let the causality code find what went wrong, assign a cause to this problem, and then attempt to fix it. But there were some very sophisticated forward pruning codes, including Berliner's PATSOC dissertation program. I think we all left that way because the codes were so big compared to the simple full-width + extension approach. But nothing says it is wrong, because _all_ forward pruning has a risk, which is provable. A non-forward pruning program simply avoids this risk, but then searches less deeply. If "less deeply" is still deeper than the rest of us, then we aren't going to be able to prove to it that our selectivity is better, since the non-pruner will find _every_ mistake we make...
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