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Subject: Re: Staged evaluation

Author: Tord Romstad

Date: 10:40:17 10/20/04

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On October 20, 2004 at 12:24:04, Alessandro Scotti wrote:

>I'm going to rewrite the evaluation function of my engine and I would like to
>know what do you think about dividing the game in stages such as for example
>middlegame#1, middlegame#2, ..., endgame#1 and so on.
>I've often read that it's better for an engine to avoid "discontinuity" in the
>evaluation, which sounds reasonable but on the other hand dividing the game in
>stages looks like a big mess and I'm not sure there won't be other side effects
>as well...

A simple way to solve this problem is to compute several values, and to
interpolate between them depending on the material left.  This is what I have
always done.  At all nodes, my evaluation
function computes two values, a midgame eval and an endgame eval.  If the total
non-pawn
material remaining is at least 2 queens + 2 rooks + 4 minor pieces, I return the
midgame eval.
If the total non-pawn material is less than 4 rooks + 2 minor pieces, I return
the endgame eval.
When the material is somewhere between, I return an interpolated value.

Tord



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