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Subject: Re: right now, at this very moment wac 141?

Author: Uri Blass

Date: 20:02:42 09/30/04

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On September 30, 2004 at 18:19:01, Robert Hyatt wrote:

>On September 29, 2004 at 19:54:50, Stuart Cracraft wrote:
>
>>On September 29, 2004 at 18:34:40, Uri Blass wrote:
>>
>>>On September 29, 2004 at 18:20:45, martin fierz wrote:
>>>
>>>>On September 29, 2004 at 16:21:43, Uri Blass wrote:
>>>>
>>>>
>>>>>I think that it is clear that extending every nate threat by a full ply will
>>>>>blow your search.
>>>>>
>>>>>If you do not use partial extensions then I suggest that you do not extend mate
>>>>>threats unless  you have some conditions to extend them only near the root and
>>>>>not every where.
>>>>>
>>>>>Uri
>>>>
>>>>i extend mate threat by a full ply always. and my search isn't blowing up, at
>>>>least not that i notice. then again, WAC 141 shows some strange behavior with my
>>>>latest version:
>>>>
>>>>MUSE 0.89.10 UCI 30 MB:
>>>>
>>>> 1   00:00 -1.65   Kg2g1
>>>> 2+  00:00 -2.36   Kg2f1
>>>> 2   00:00 -2.36   Kg2f1 Nf4d3
>>>> 3   00:00 -1.22   Kg2f1 Re8b8 Kf1e1
>>>> 4   00:00 -2.13   Kg2f1 Kg8h7 Bb3d1 Nf4d3
>>>> 5   00:00 -2.16   Kg2f1 Re8e2 Kf1g1 Nf4d5 Kg1f1
>>>> 6+  00:00 -1.66   Qc1xf4
>>>> 6   01:24  M6  Qc1xf4 Bd6xf4 Rh4xh5 g6xh5 Rh1xh5 Bf4h6 Rh5xh6
>>>>
>>>>it sees Qxf4 after 0 seconds (this is on a slowly 1.4GHz P4), but needs a very
>>>>long time to resolve it. but at least it sees Qxf4 in 0 seconds :-)
>>>>
>>>>cheers
>>>>  martin
>>>
>>>If you extend also checks by  a full ply then there are cases when there is a
>>>long sequence
>>>check ,escape threat mate,check,escape threat mate and it means that you may
>>>have big problems to search deep in position when one side threats mate but the
>>>opponenthas a lot of checks because he tries to do perpetual checks.
>>>
>>>You can easily search some lines to more than 100 plies at small depth and  I do
>>>not believe that it is a good idea.
>>>
>>>Uri
>>>
>>>
>>>Uri
>>
>>This is very useful. Okay, in main search I can just start off with
>>revaluing check extension to 0.75 instead of 1 but I'd expect that
>>since I have few extensions, very few checks would be searched.
>>How would you handle reducing check extension value in such an
>>arrangement.
>>
>>Also, my quiescence search always investigates all check evasions
>>to any depth. Should I be doing that?
>
>Absolutely not.  IE you capture at first q-search ply where you can also stand
>pat.  Your opponent captures at the next ply and you try all moves to get out of
>check and eventually find a deep mate.  It isn't forced as you can just stand
>pat at the first capture and all that searching was wasted...

The searching was not wasted unless standing pat is better because you learned
that the capture is not good.
Let take 2 examples

[D]r5k1/6pp/4b3/7q/8/4R3/5PPP/N2B2K1 w - - 0 1

If you search check evasion you can find that BxQ is bad and return the stand
pat score that is bad for white.

[D]r5k1/6pp/4b3/7p/8/4R3/5PPP/N2B2K1 w - - 0 1

In this case of course you do not search after Bxh5 RxN+ because there is no
check evasion to do the score above alpha and alpha in the beginning was the
standpat score or something higher.

Uri



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