Author: Martin Giepmans
Date: 15:39:13 11/20/02
Go up one level in this thread
On November 20, 2002 at 17:45:02, Omid David Tabibi wrote: >On November 20, 2002 at 17:39:26, Martin Giepmans wrote: > >>On November 20, 2002 at 16:19:29, Omid David Tabibi wrote: >> >>>On November 20, 2002 at 16:04:50, Martin Giepmans wrote: >>> >>>>On November 20, 2002 at 11:43:10, Omid David Tabibi wrote: >>>> >>>>> >>>>> ICGA Journal, Vol. 25, No. 3, pp. 153-161, September 2003 >>>>> >>>>> >>>>> Verified Null-Move Pruning >>>>> >>>>> Omid David Tabibi and Nathan S. Netanyahu >>>>> >>>>> >>>>> Abstract >>>>> >>>>>In this article we review standard null-move pruning and introduce our extended >>>>>version of it, which we call verified null-move pruning. In verified null-move >>>>>pruning, whenever the shallow null-move search indicates a fail-high, instead of >>>>>cutting off the search from the current node, the search is continued with >>>>>reduced depth. >>>>> >>>>>Our experiments with verified null-move pruning show that on average, it >>>>>constructs a smaller search tree with greater tactical strength in comparison to >>>>>standard null-move pruning. Moreover, unlike standard null-move pruning, which >>>>>fails badly in zugzwang positions, verified null-move pruning manages to detect >>>>>most zugzwangs and in such cases conducts a re-search to obtain the correct >>>>>result. In addition, verified null-move pruning is very easy to implement, and >>>>>any standard null-move pruning program can use verified null-move pruning by >>>>>modifying only a few lines of code. >>>>> >>>>> >>>>>pdf: http://www.cs.biu.ac.il/~davoudo/pubs/vrfd_null.pdf >>>>>zipped pdf: http://www.cs.biu.ac.il/~davoudo/pubs/vrfd_null.pdf.zip >>>>>gzipped postscript: http://www.cs.biu.ac.il/~davoudo/pubs/vrfd_null.ps.gz >>>> >>>> >>>>If I'm not mistaken this is the well known "verification search" with >>>>one modification: no verification in the verification search. >>>>Am I right? >>>> >>> >>>The classical verification search as introduced by Plenkner comes to detect >>>zugzwangs. Verifeid null-move pruning as presented in the paper, constructs a >>>smaller search tree with greater tactical strength in middle games (in addition >>>to detecting zugzwangs). >>> >>> >>>>Another question: >>>>your results in table 5 seem convincing, but what about table 4? >>>>Are these results statistically significant? (my guess is no ..) >>>> >>> >>>For a good estimate of the growth of the search tree as we go deeper, see Table >>>3 and Figure 4 (which present ECM test positions searched to a depth of 11 >>>plies). >>>The WCS test positions were mainly used for testing the tactical strength >>>(results in Table 5). Table 4 was provided just for the sake of completeness. >>> >>> >>>>Martin >> >>I see that I reduced the numbers of the tables (R=1 ;)) >>What I wanted to write is that table 6 is convincing while table 5 is IMO not. >> >>Combining table 4 and 5 my impression is that - from a time perspective - >>R=3 might be better than verified R=2. > >(you mean verified R = 3, don't you?!) > >Even though standard R = 3 constructs a smaller search tree, the problem with >it, is that it is too risky. Except DIEP which uses a fixed R = 3, I don't know >of any program that uses that value due to its high risk. > > >>Compared to R=3 verified R=2 solves about 3% more positions but is about 40% >>slower! >> >>Martin Yes, of course I mean verified R=3 (I did it again ;)). What about my last remark (the percentages)? From a time perspective your results may indicate that vrfd R=3 is actually _worse_ than R=3. OK, R=3 is risky, but for the prize of an occasional oversight (3%) you get a speedup of about 40% (according to your tables). The prize for 40% speedup is 1 or 2 extra plies in 3% of the positions ... I think if you do the math you will see that that is very cheap. In a tournament game with clocks R=3 is indeed risky. One oversight is often enough to lose a game. The question is how a (less risky) combination of R=2 and R=3 compares to your method. Martin
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