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Subject: Re: WAC 141 blowup

Author: martin fierz

Date: 12:31:31 09/02/04

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On September 02, 2004 at 09:45:25, Michael Henderson wrote:

>On September 02, 2004 at 02:39:28, martin fierz wrote:
>
>>On September 01, 2004 at 10:11:18, Uri Blass wrote:
>>
>>>On September 01, 2004 at 05:57:25, martin fierz wrote:
>>>
>>>>On September 01, 2004 at 00:51:47, Stuart Cracraft wrote:
>>>>
>>>>[snip]
>>>>
>>>>Muse on P4 2.4GHz finds the mate at ply 6, failing high on Qxf4 after 0.7
>>>>seconds (not shown in the logfile).
>>>>
>>>>the reason it can solve this at such a low search depth is probably twofold, the
>>>>first is that it generates checks in qsearch on the first ply of the qsearch (so
>>>>when you drop directly into qsearch with a nullmove, it will see Rh8# every
>>>>time), the second is probably that it is using mate-threat extensions.
>>>>
>>>>cheers
>>>>  martin
>>>
>>>Do you get 2 plies only by mate extensions?
>>>In order to do it you need to extend 2/3 ply for mate threat.
>>>
>>>The line 1.Qxf4 Bxf4 2.Rxh5 gxh5 3.Rxh5 Bh6 4.Rxh6 is 7 plies and qsearch here
>>>does not see mate because it is black to move so I need 8 plies even if I
>>>disable pruning by evaluation.
>>
>>hi uri
>>
>>the reason must be that after 2.Rxh5 i get a mate threat extension and after
>>3.Rxh5 again, and since i do a full ply for that, my program sees it.
>>
>>cheers
>>  martin
>>
>>>
>>>With pruning by evaluation latest movei get it only in 10 plies but I think to
>>>change my pruning to make it see it faster.
>>>
>>>Uri
>
>is recapture extension also playing a role here?...if that applies.

it doesn't apply for me, but it probably depends on what an engine would
classify as a "recapture". some people might call any sequence of two captures
on the same square a recapture, for me a recapture is only if a piece of the
same value is recaptured. this isn't the case here.

cheers
  martin



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