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Verification search
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Lucas Braesch



Joined: 31 May 2010
Posts: 1734
PostPost subject: Re: Verification search    Posted: Fri Jun 15, 2012 4:00 am Reply to topic Reply with quote
bob wrote:
lucasart wrote:
Just tried it, and it's proven completely useless. Result after 500 games in 6"+0.1" (average NPS on my hardware around 1M)
Code:
Score of test vs DiscoCheck 3.5.1: 152 - 149 - 199  [0.50] 500

I wonder if it's normal, and if others have come to the same conclusion, or if I'm doing something wrong.

Basically I'm doing a verification search at high depths (depth >= 7) when the null move fails high.


I personally tested this several times, with 30K game matches, and I found absolutely no case where it helped, and lots of cases where it hurts (you can limit the overhead by limiting the depth where you do it of course)...

I think this whole zogzwang problem is vastly exagerated. People seem to attach far too much attentionattention to this post null move hype:After testing I discovered the following:
* verification search is completely useless. elowise of course, meaning that there are perhaps some positions in which it helps, but overall it doesn't help.
* the piece precondition: only do a null move when you have at least a piece on the board. Well even that is almost useless. Adding that condition was unmeasurably better (better but below error bar). I kept it anyway, but perhaps it could be further improved, like at least one piece, or not in a king opposition (ie. king dist != 2). Even in K+P endgames, the zugzwang is more an exception than a general problem. And not doing null move misses a lot of good moves that would be found deeper in search, which is to be put in front of the zugzwang improvement.
* when null move fails low, do a mate threat extension (ie. search for a mate at null-reduced depth from opp perspective): saw that in the wiki, and found it to be not just useless but actually harmful. There is however the connected move trick by Tord Romstad, which is quite a smart idea. I haven't experimented with it, and wonder how much elo it adds to SF.
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Subject Author Date/Time
Verification search Lucas Braesch Thu Jun 14, 2012 1:07 pm
      Re: Verification search Robert Hyatt Thu Jun 14, 2012 1:19 pm
            Re: Verification search Pawel Koziol Thu Jun 14, 2012 2:54 pm
            Re: Verification search Lucas Braesch Fri Jun 15, 2012 4:00 am
                  Re: Verification search Eelco de Groot Fri Jun 15, 2012 12:54 pm
                  Re: Verification search Daniel Homan Fri Jun 15, 2012 3:00 pm
                  Re: Verification search Lucas Braesch Sat Jun 16, 2012 3:18 am
                        Re: Verification search Vincent Diepeveen Thu Jun 21, 2012 2:47 pm
                              Re: Verification search Larry Kaufman Sat Jun 23, 2012 5:06 am
                                    Re: Verification search Vincent Diepeveen Sun Jun 24, 2012 10:32 am
                                          Re: Verification search Larry Kaufman Sun Jun 24, 2012 2:40 pm
                                                Re: Verification search Vincent Diepeveen Tue Jun 26, 2012 10:40 am
                                                      Re: Verification search Don Dailey Tue Jun 26, 2012 11:09 am
                                                            Very minor verification search modification. Eelco de Groot Tue Jun 26, 2012 4:47 pm
                                                                  Re: Very minor verification search modification. Vincent Diepeveen Wed Jun 27, 2012 1:30 am
                  Re: Verification search Vincent Diepeveen Sat Jun 16, 2012 2:58 pm
      Re: Verification search Karlo Bala Jr. Fri Jun 15, 2012 7:30 am
            Re: Verification search Lucas Braesch Fri Jun 15, 2012 11:02 am
                  Re: Verification search Pawel Koziol Fri Jun 15, 2012 12:13 pm
                  Re: Verification search Karlo Bala Jr. Fri Jun 15, 2012 1:58 pm
      Re: Verification search J. Wesley Cleveland Sat Jun 16, 2012 12:12 am
      Re: Verification search Don Dailey Sat Jun 16, 2012 10:32 pm
            Re: Verification search Lucas Braesch Sun Jun 17, 2012 3:13 am
                  Re: Verification search Don Dailey Sun Jun 17, 2012 3:41 am
                  Re: Verification search Miguel A. Ballicora Sun Jun 17, 2012 4:21 am
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