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Subject: Re: Too Large Positional Contributions to Score

Author: Peter McKenzie

Date: 20:37:39 03/07/99

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On March 07, 1999 at 23:29:31, Stuart Cracraft wrote:

>Crafty seems to have a Scale_Up/Scale_Down factor and I'm curious
>if Bob would talk a little about this. Seems costly to add a memory
>reference and a division (?).

I'm guess his divisions are usually by a constant that is a multiple of 2, in
which case the compiler will just do a bit shift.

>
>For example, seems like Bob has chosen to ScaleUp/ScaleDown fairly
>large contributions such as
>
>   weak back rank
>   bishop pair
>   certain rooks on open files
>   rook on 7th
>   protected passed pawns
>
>based on the side's material.
>
>Are there alternatives to controlling the "bloating" of the positional
>part of the evaluation that aren't so computationally expensive? I know
>there are very few of these compared to all the terms in Crafty so the
>cost isn't a big deal (probably.)
>
>One I considered was going from centipawns to millipawns and then working
>backward looking at just those things that should be big (king safety)
>and sizing them accordingly letting them bloat to a certain degree beyond
>a pawn.
>
>--Stuart



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