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Subject: Re: Qsearch Checks

Author: Stuart Cracraft

Date: 08:47:42 09/05/04

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On September 04, 2004 at 18:30:36, Uri Blass wrote:

>On September 04, 2004 at 18:20:49, Stuart Cracraft wrote:
>
>>On August 31, 2004 at 19:43:08, Uri Blass wrote:
>>
>>>On August 31, 2004 at 19:25:39, Stuart Cracraft wrote:
>>>
>>>>On August 30, 2004 at 15:53:13, Uri Blass wrote:
>>>>
>>>>>On August 30, 2004 at 15:34:22, Stuart Cracraft wrote:
>>>>>
>>>>>>On August 30, 2004 at 12:21:01, Uri Blass wrote:
>>>>>>
>>>>>>>On August 30, 2004 at 07:36:45, Volker Böhm wrote:
>>>>>>>
>>>>>>>>Hi Uri,
>>>>>>>>
>>>>>>>>do you allways check all evades in qsearch or only until a certain ply as for
>>>>>>>>checking moves?
>>>>>>>>
>>>>>>>>Greetings Volker
>>>>>>>
>>>>>>>only until a certain ply but that ply is late.
>>>>>>>I also do not check all captures and do it only until a certain ply.
>>>>>>>
>>>>>>>I practically have 2 functions of qsearch
>>>>>>>int Quies(int alpha, int beta,int depth)
>>>>>>>
>>>>>>>int quiesmall(int alpha,int beta,int depth)
>>>>>>>
>>>>>>>Quies search checks and captures and when the depth is small enough Quies calls
>>>>>>>quiesmall (quiesmall does not make checking moves that are not captures but it
>>>>>>>calculate all replies to check unless the remaining depth is small enough and
>>>>>>>when the remaining depth is 0 even captures are not tried.
>>>>>>>
>>>>>>>
>>>>>>>Quies usually starts with depth=7 when depth=5 I call quiesmall and when
>>>>>>>depth<=2 I do not generate replies to check and when depth=0 I do not make more
>>>>>>>captures and retrun static evaluation+pawn with the idea that the side to move
>>>>>>>may earn something by a capture but I do not know how much.
>>>>>>>
>>>>>>>It may be better to use static exchange evaluator but it is not very important
>>>>>>>and most qsearch do not get to the place when depth=0 or the result of the
>>>>>>>evaluation when depth=0 is not important for the final score.
>>>>>>>
>>>>>>>
>>>>>>>Uri
>>>>>>
>>>>>>So for all the trouble you have gone to to do all of the above, can you
>>>>>>point at specific measurable achievements you have gained from it?
>>>>>>
>>>>>>Stuart
>>>>>
>>>>>I know that checks in the first plies of the qsearch improved the strength of
>>>>>movei(the improvement was obvious in test suites and I believe that it also
>>>>>helped in games but I did not play enough games to test it)
>>>>>
>>>>>I remember that a buggy implementation that could return wrong mate scores did
>>>>>not change much the strength in games and I later fixed bugs.
>>>>>
>>>>>I think that the main improvement was that after adding checks in the qsearch I
>>>>>changed null move with R=2 to null move with R=3 and R=3 was obviously better
>>>>>with checks in the qsearch(I did not check without them but I read or got the
>>>>>impression that other programs found that R=3 is better with checks in the
>>>>>qsearch when R=2 or E=2/3 is better without them).
>>>>>
>>>>>limiting the qsearch was always part of movei because I did not want the search
>>>>>to explode in Leonid'a positions when both sides have many queens.
>>>>>
>>>>>Movei has problems to go deep in Leonid's position but it has no problem of
>>>>>needing an hour to find mate in 1 that happened to Fritz in one similiar
>>>>>position that was discussed here(Leonid usually gave harder problems than mate
>>>>>in 1).
>>>>>
>>>>>Uri
>>>>>
>>>>>Uri
>>>>
>>>>Uri,
>>>>
>>>>For short searches of 1 second on my box, I've found adaptive null move
>>>>with varying R to give better results than verified null move with R=3.
>>>
>>>Note that I use verified null move pruning only in the endgame and in the
>>>middlegame I use null move pruning with no verification.
>>>
>>>I did not test a lot of possibilities there and I only know that R=3 is
>>>significantly better than R=2 and I also read that people who do checks in the
>>>qsearch tend to prefer R=3(you do not do checks in the qsearch and I mean not to
>>>replies to check).
>>
>>Uri,
>>
>>My program has this in relation to checks, all conditionally compilable:
>>
>>  1) all checks-evasions in quiescence, unlimited occurrences
>>  2) all checks-evasions in main search, unlimited occurrences
>>  3) all checking-moves in quiescence, at the first ply of quiescence
>>
>>These are the three extensions. Only #1 and #2 have proved useful.
>>
>>Stuart
>
>If your qsearch can call the main search then it is clear that 3 is not useful
>because your search will explode by the following sequence:
>
>1.Qsearch checking move first ply
>2.main search escape from check.
>3.Qsearch checking move first ply because it is a new qsearch.
>4.main search escape from check.
>...
>
>If you want to use checks in the first ply of the qsearch then the qsearch
>should never call the main search.
>
>Uri

Uri,

I should try tinkering with a qsearch that, if in check upon entry, simply
generates check avoidance moves internally.

Thanks,

Stuart



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