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Subject: Re: How I Learned to Stop Hating 141

Author: Stuart Cracraft

Date: 07:22:29 09/03/04

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On September 03, 2004 at 09:19:00, Andrew Platt wrote:

>On September 03, 2004 at 08:46:08, Uri Blass wrote:
>
>>>It would be too expensive for me to really deal with checks in qsearch because I
>>>don't want to have to generate the legal capture modes. All I do is bomb out of
>>>it if I see the King being captured. However, it might not be too expensive to
>>>generate the legal moves at the first ply of qsearch if we're in check to catch
>>>these conditions. I might try that and see if it causes testsuites to slow down
>>>much.
>>>
>>>Andy.
>>
>>You do not need to do it.
>>If you extend every check by 1 ply in correct way there is 0 chance to get
>>position when the king is in check in the first ply of the qsearch.
>
>You're right. Late nights analyzing plies of trace data do strange things to the
>mind! The real situation I was seeing was a standard horizon effect exacerbated
>by null move. With null move I don't see Rh8# and extend for a mate threat if I
>don't have enough depth to call alpha-beta from the null move since the qsearch
>doesn't generate non-capturing checking moves.
>
I added this features, generating non-capturing checking moves, at
the first quiescence ply -- it failed to solve 141.

So far, only recapture (two back-to-back captures on the same square,
any pieces) solves it in under 3 minutes on this box.



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