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Subject: Re: Correct values if all moves are pruned?

Author: Ernst A. Heinz

Date: 18:38:12 01/08/01

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Hi Severi,

>1.If I prune a move in normal search: if(material+gain(move)+FMARGIN<=alpha)
>what should I assign to the best score so far? Material+gain, material+FMARGIN,
>material+gain+FMARGIN or material only? Now I'm using material+FMARGIN but it
>can't be right.

As described in my texts about extended futility pruning,
"DarkThought" (http://supertech.lcs.mit.edu/~heinz/dt/)
initializes the best score so far with:

"mat_balance(node) + <margin>"

for normal and extended futility pruning as well as limited
razoring. This provides a reasonable fall-back if all moves
get pruned or all non-futile moves fail low. You could
possibly improve on the value by adding the max. material
gain of all futile captures.

=Ernst=



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