Author: Robert Hyatt
Date: 06:54:25 10/18/00
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On October 18, 2000 at 08:06:23, David Rasmussen wrote: >I was wondering about a potential "bug" or at least "unwanted feature" of the >way hashing and extensions affect eachother in, say, Crafty. > >The problem is basically this: > >In Crafty, whenever depth is used for other purposes than searching (that is >hashing and nullmove), the extension factor isn't included. That means that a >search that essentially asked for a depth=5 + extensions=3 == 8 ply search, will >return with success from the hashprobe if the draft is just 6 or 7. Shouldn't >the depth parameter ALWAYS be used with relevant extensions for the search to be >(at least more) theoretically correct ? > >Am I making sense? You are missing an important point. Extensions happen _after_ a move is made. Hashing happens at the start of a ply. If extensions were added in at any previous ply, they are certainly factored into the hash probe. But there is no way to factor in extensions triggered by a move, when the hash probe is done _before_ any move is made. IE if an in-check extension is done, it is added in at the _previous_ ply, rather than at the current ply. Which means it is _always_ done. The only exception is that the one-reply extension isn't done until crafty discovers that there is only one legal move. But this is perfectly consistent... Don't forget that the hash entry will be the result of searching _all_ moves at this ply, which _does_ factor in the extensions for each move as appropriate...
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