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Subject: Re: Crafty Book Implementation

Author: Robert Hyatt

Date: 05:50:15 06/12/01

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On June 12, 2001 at 06:00:44, David Rasmussen wrote:

>On June 11, 2001 at 20:48:19, Robert Hyatt 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?
>>>
>>>I'm having an idea of another book implementation that I think is quite smart,
>>>but I won't reveal anything yet, primarily because I don't know if it works in
>>>practice, secondarily because it might not be a new idea, tertiarily because it
>>>might not be a smart idea at all :)
>>
>>
>>I _intentionally_ want to miss those transpositions.  One classic:
>>
>>1. e4 e5 Nf3 a6 Bb5.  Do you _really_ want to transpose back into the book
>>and play Nc6?  Or do you want to rip the bishop and be a piece up in a won
>>game?
>>
>>:)
>>
>>My thinking when I did this scheme was "Crafty will probably play Nc6 if it
>>is reasonable, and _then_ we will transpose back into book after white plays
>>Ba4, because that is a normal position.  But the position given above is
>>"not normal" and I won't try to transpose.
>>
>>It has happened in _real_ games in the past.  But it won't happen to me
>>here. :)
>
>But still, you're saying: "I'm afraid of that situationm so I won't do _any_
>transpositions from non-book positions to book positions", which is not as nice
>as being able to do it from everywhere, while still taking care of the problem
>you mention. I don't have a solution for this, but don't you think a solution
>with those properties would be nicer?


I don't see how it is possible.  I can currently transpose from any known book
line to any other known book line, with zero difficulty.  The only requirement
is that the position before I make a move must be a known book position, and the
position after I make a move must be one also.

Allowing others (ie full transpositions) is dangerous due to the given position
where Nc6 is book _and_ BAD.




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