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

Author: Alessandro Damiani

Date: 13:59:57 11/21/02

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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.


>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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