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Subject: Re: Question: What part of the eval score is used for calculating Delta

Author: Ross Boyd

Date: 15:57:22 05/22/05

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On May 22, 2005 at 15:10:37, William Bryant wrote:

>My eval has 4 components:
>Material
>King Safety
>Pawn
>Piece Position Score.
>
>Does everything except the Material go into the calculation of greatest
>positional score (for delta pruning int he Q search), or just the material and
>or the pawn values.
>
>William

Everything except material.

Basically, with delta pruning you are pruning moves that don't have a hope of
reaching alpha - even after a full positional evaluation and taking into account
potential capture/promotion  values.

So, you keep track of the highest positional score the search has achieved and
use that as the 'margin' for error.

You might add other conditions to delta pruning, eg. avoid delta pruning of
tactical moves or check evasions or if there are mate threats.


Ross




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