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Subject: Re: How to detect combinations?

Author: Tony Werten

Date: 00:27:33 08/03/01

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On August 03, 2001 at 01:08:22, Pham Minh Tri wrote:

>Hi all,
>
>I saw that my weak engine quickly lost some games or missed some other victories
>by not recognising many common combinations. I have written codes for detecting
>them and tried many extensions. Unfortunately, they made the search tree grew
>exponentially (2-6 times slower) but did not help much, many combinations were
>still 4 or 5 plies deeper than the full search deep (8-9, some branches are
>extended to 13-15). The situation was even worse when a combination did not make
>any check or capture before mate.
>
>Could someone give me some suggestions/comments?

Well, at least a useless one: You have to search deeper.

Be carefull with extensions though. You have to limit them. The idea behind most
extensions is to find something that otherwise would be hidden behind the
horizon.

A threat extension is a clear example of this (after heavy fail low on nullmove
). If you do nothing you'll be checkmated, so extend. But do you really want to
do that when there are still 8 plies of search left ? Those 8 ply should find
the correct continuation, not your extension.

Tony


>Thanks in advance.
>Pham



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