# Computer Chess Club Archives

## Messages

### Subject: Re: Verified Null-Move Pruning, ICGA 25(3)

Author: Robert Hyatt

Date: 17:03:23 11/21/02

Go up one level in this thread

```On November 21, 2002 at 16:59:57, Alessandro Damiani wrote:

>On November 21, 2002 at 16:19:00, Robert Hyatt wrote:
>
>>On November 21, 2002 at 05:14:53, Alessandro Damiani wrote:
>>
>>>On November 20, 2002 at 18:59:59, Uri Blass wrote:
>>>
>>>>On November 20, 2002 at 17:51:40, Alessandro Damiani wrote:
>>>>
>>>>>>
>>>>>>One final remark: You use standard R = 3 in DIEP. So the search tree constructed
>>>>>>by your program will definitely be smaller than that of verified R = 3. Many
>>>>>>people find standard R = 3 as too risky; but if you are happy with its overall
>>>>>>tactical strength, then I don't recommend you to shift to another method. But
>>>>>>for those who'd like to get greater tactical strength than standard R = 2, and a
>>>>>>smaller search tree than R = 2, I recommend to try verified null-move pruning.
>>>>>>
>>>>>>Best,
>>>>>>
>>>>>>Omid.
>>>>>>
>>>>>
>>>>>Vincent uses R = 3 and complex quiescence search (Vincent, correct me if I am
>>>>>wrong). Maybe your Verified Null-Move gives about the same results like R = 3
>>>>>with a complex quiescence search.
>>>>>
>>>>>_If_ this is true then your approach is simpler and therefore better. Just my
>>>>>two thoughts before going to bed. Good nights.......
>>>>>
>>>>>Alessandro
>>>>
>>>>I do not believe that it gives the same results.
>>>
>>>I wrote "about the same result" which is not equal to "the same result". And I
>>>added "maybe". These words tells you that I am just guessing, nothing more,
>>>nothing less.
>>>
>>>
>>>>I do not know which algorithm is better but the
>>>>algorithms are different.
>>>>
>>>
>>>Right, to know and to guess are two different things. I am in the guess-phase.
>>>;)
>>>
>>>
>>>>I believe that a third algorithm may be better than both of them.
>>>>
>>>
>>>BTW I won't use it. My preferred algorithm is Alpha Beta Conspiracy Search
>>>(ABC), and ABC already contains Verified Null-Move in a different way.
>>>
>>>BTW Verified Null-Move looks like an improvement of Fail High Reductions by the
>>>authors of Zugzwang.
>>>
>>>Alessandro
>>
>>
>>If you mean because while verifying at one node you don't verify anywhere deeper
>>I
>>agree.  I tried the FHR and threw it out as too expensive when it first surfaced
>>several
>>years ago.  This approach bears some testing however...
>>
>
>I just noticed several things both approaches have in common, and IIRC the
>authors of FHR mentioned for future research to replace the test
>
>    staticScore(position) - staticThreats(opponent) >= beta
>
>by a search. This ends up with using dynamic null-move. IIRC they used static
>mate threat detection for their staticThreats(opponent).
>
>To be clear, every improvement is an improvement and deserves its merit. I just
>think that FHR should have been mentioned in Omid's paper, since they have some
>concepts in common.

I would agree there.  however, I wasn't a reviewer so I didn't have an
opportunity to
suggest that...  It's always good to be complete in a literature review for a
paper,
of course...

>
>
>>Unfortunately I have not yet made any progress.  Been busy writing
>>justifications for the
>>new ftp server to house all of Eugene's 6-piece EGTB stuff.  :)
>
>hehe I read about Eugene pumping iron..ahem EGTB. :)
>
>Alessandro

```

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