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Subject: Re: Crafty Book Implementation

Author: Robert Hyatt

Date: 17:50:17 06/11/01

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On June 11, 2001 at 17:44:55, J. Wesley Cleveland wrote:

>On June 11, 2001 at 14:17:37, David Rasmussen wrote:
>
>>Am I an idiot, or does that Crafty book scheme miss some transpositions, because
>>of it's clustering system? Wait, those two statements aren't mutually
>>exclusive...
>>
>>When some of the upper bits of the book hashkey, is from the parent position,
>>doesn't that mean that if I'm in an unknown position, that can make a move that
>>transposes into a book position, it won't, because the upper bits will only
>>match the actual parent position(s) from when the book was created?
>
>Right, the only transpositions crafty finds are those that have been played in
>the pgn the book was created from. This prevents crafty from making stupid
>transpositions, e.g. e4 e5 Nf3 Nc6 Ng1 Nb8??

Not quite.  The above is found because Nb8 is a two-fold repetition and the
book code won't play it.  If that is the only move, crafty will have to do a
search to find another, although the search will recognize that Nb8 is not
a true draw since it is only the second repetition.

Crafty will transpose from line to line, opening to opening, just like any
human will  But it has to be a legitimate transposition, not one like the
other example I gave in a previous post...




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