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

Author: Omid David Tabibi

Date: 03:52:57 11/22/02

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On November 22, 2002 at 06:45:30, Gian-Carlo Pascutto wrote:

>On November 22, 2002 at 01:48:06, Robert Hyatt wrote:
>>It isn't what he is claiming.  He claims that R=3 + verification is close to
>>R=2 in nodes, and has fewer null-move failures.  His data seems to support >that.
>>R=3 with a depth-1 verification ought to be fairly close to R=2, just based on
>>pure math.  I'll leave it to you to figure out why...
>I don't really agree.
>I'm assuming you do the fairly intuitive math of 2+1=3 but things
>are not so simple :)
>R=3 verif. does a R=3 search, one depth reduction on fail high (which
>makes it equivalent to R=1 without nullmoving at that ply, but it is
>safe because you guaranteed your opponent has no serious threat), and
>R=3 cutoffs everywhere below
>R=2 does, well, R=2 cutoffs
>It's not so obvious these are close in nodes. In fact, the paper itself
>points of that the methods scale very differently.

Many things are not that obvious. Please read the "Conclusions" section for
other algorithms I tried but were inferior to the presented algorithm.

One interesting point is that at depth 8, the size of the tree constructed by
vrfd R=2 was slightly larger than std R=2; at depth 9, vrfd constructed a
smaller tree, and the gap widens as we search deeper (see Figure 4). So, I
believe than on every program, starting from a certain depth, vrfd R=3 will
construct much smaller trees in comparison to std R=2. And the benefit will
increase as we search deeper.


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