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Subject: Re: Restricting extensions

Author: Uri Blass

Date: 02:25:42 09/13/04

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On September 13, 2004 at 01:59:27, Volker Böhm wrote:

>On September 12, 2004 at 19:39:10, Scott Gasch wrote:
>
>>On September 12, 2004 at 18:19:04, Volker Böhm wrote:
>>
>>>Hi Scott,
>>>
>>>the idea behind a check-extension is not only to find great attacks beginning
>>>with a checking move. One other major idea is to prevent horizont effects.
>>>Example: you give away a piece for a really good attack. But the opponent has
>>>the opportunity to give you some checks, pushing the really good attack out of
>>>sight. Extending the checks in positions below alpha helps to fix this problem.
>>>
>>>I never found a good idea to reduce check extension.
>>
>>I always extend a checking move 1 ply.  What I'm talking about is deciding to
>>either extend or not extend the one legal response on the next ply.  I agree
>>with you about checks: I've never found a way to safely not extend them.  Even
>>if the checking side is way ahead it could be checking just to push something
>>really bad over the horizon.
>
>Hi,
>the 1 legal response extension is good to prevent horizont effects too. Maby
>that is why your extension-reduction code does not give good effects.

My experience is different.
Extensions can be productive to prevent horizon effect but counter productive
by extending stupid lines and the question is what is more important.

I think that if the advantage of the attacker is big enough you can be
practically sure of no horizon effect.

I decided to stop check extensions when the side that gives check has very big
advantage(very big advantage is clearly more than a bishop) because in 99.9999%
of the cases the extensions are not to prevent horizon effect.

Movei may be slower in finding some mates because of it but I care about games
and not about finding mates.

I also think that it is possible to have some function to detect suspect for
horizon effect when you are in check and use the result of that function to
decide if to extend or not to extend.

Uri



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