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Subject: Re: When to stop searching?

Author: Volker Böhm

Date: 05:18:48 05/03/04

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On April 30, 2004 at 08:26:59, Bernd Nürnberger wrote:

>Hello,
>
>I am wondering when to stop searching further in iterative deeping
>and whether to stop or not at a certain point.  I recognized that
>many engines often play moves very quickly while spending much time
>on other moves.
>
>If the iterative deeping process stays with a certain move for
>several plies and the score returned by alphabeta does not vary
>to much, can I stop the process?
>
>Are there more sophisticated methods?
>
>Greetings,
>         Bernd
Hi,

you can nearly never stop searching "earlier" except if and only if there is a
recapture that proves to be the only move not loosing material.
Even if alphabeta don´t varry much your engine could just find a tactical
problem in the next millisecond.

There are two point where you should search (much) longer.

1. Your best move calculated from the previous interation fails low. At this
point you should spend enough time to be sure that all other moves are searched
too.
2. If after your iteration the result drops below your initial alpha value. Then
you should spend enough time to search again with a larger window. When the
result is much smaller than before, you should consider to search the next
iteration too.

Greetings Volker



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