Computer Chess Club Archives




Subject: Comments on delta pruning

Author: Bas Hamstra

Date: 02:14:23 10/05/99

I have been thinking about "Delta pruning". The way I saw it (a while ago) in
Crafty is like this:

	Delta = Alpha - Material - Margin;

Then for each capture:

	if(CaptureValue < Delta) skip this capture.

Now I would like a raction to the following statements:

(Material - Margin) is a cheap estimation of the current eval. If positional
bonusses get frequently more than a pawn (or even more) "Margin" should be set
to near the maximum the positional part of the score can be, or else this
estimation can become very inaccurate and introduces much errors. Reaction?

If positional bonusses get frequently much more than a pawn, maybe it is more
accurate to use this:

	Delta = Alpha - Eval;

Because with one move the Eval won't change *that* much. Reaction?

Bas Hamstra.

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