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Subject: Re: Changing Score at Horizon, after finishing Q-Search? Alpha/Beta Values?

Author: Daniel Pineo

Date: 08:04:36 04/06/05

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  There is an alternative way of thinking about this.  This is equivalent to a
fixed depth search ending in an evaluation, but where the calculation of the
material term is more than just adding up material, but actually recurses deeper
into the position to get a more accurate value by taking into account exchanges.

  Of course, viewed like this, it seems like you're doing a lot of work for that
one material term.  And the question becomes, if you're going to do all the work
to recurse into the tree to get a more accurate material term, then why not get
more accurate positional terms while you're there?  Of course, then you're just
doing a normal qsearch.


>Hello!
>Right now im working on a new Version of my Chess Engine and an idea has come to
>my mind, but i dont know if its applicable:
>When I'm in Q-Search i only want to deal with material values. I handle theses
>incrementally, so theres is no need for any function call except the Q-search
>recursion.
>After returning from Q-Search (at the full-width horizon) i simply add the
>positional eval score to the score returned from Q-search. This score is
>returned "up the tree".
>For the positions before the horizon this should be no problem concerning
>alpha/beta values etc... . Also positions beyond the horizon should not suffer
>from this, as long as the alpha/beta values were not passed to a Node before the
>horizon before. If they were, the alpha/beta bounds would not be correct,
>because they include positional scores which are not considered beyond the
>horizon.
>So my idea is to simply substract the local positional score from the alpha/beta
>values (as long as they are not -INF or +INF) at the full-width horizon, before
>entering Q-Search. I assume that this would result in correct cutoffs.
>Is this idea correct?
>I didnt find any drawbacks yet, but i only have a vague intuition about it.
>I really would appreciate if anybody could help me with this.
>greets
>johannes



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