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Subject: Re: Reductions: when to do them?

Author: Volker Böhm

Date: 01:50:00 06/19/05

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Hi,

Reduction are one of the most compicated stuff in computer chess. A reduction
that works well for one engine may not work for yours.

I suggest the following:

1. Don´t do reductions if in a PV path in the search tree
2. Use the "far below alpha" reduction only in the last ply´s of the search tree
(this is called futility, extended futility, razoring). Reduce if the color to
move is far below alpha and cannot get near to alpha with the current move. The
"far above beta case" should be done by nullmove
3. Select other reduction priciples at lower depth of the search tree, perhaps
history pruning. (Reduce search depth of moves with a low historically measured
probability to get above beta).

Greetings Volker



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