Author: Omid David Tabibi
Date: 16:31:30 11/20/02
Go up one level in this thread
On November 20, 2002 at 19:25:28, Martin Giepmans wrote: >On November 20, 2002 at 18:49:15, Omid David Tabibi wrote: > >>On November 20, 2002 at 18:39:13, Martin Giepmans wrote: >> >>>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. >>> >> >>By "combination of R=2 and R=3" you mean adaptive null-move pruning, don't you? >>Verified version has a greater average tactical strength than standard R=2 (and >>thus greater than adaptive R=2~3), and its tree size is smaller using simple >>quiescence search. >> >Is adaptive R=2/3 tactically stronger if you include the time factor? >As I allready pointed out: your tables seem to indicate that pure R=3 >is stronger that vrfd R=3. >If if if you include the time factor. >Adaptive nullmove migth also be stronger if if if ... > >Do we agree that time matters? >Of course if you like we can continue this conversation in heaven :) > Usually people don't get good results with standard R=3 due to its great tactical weaknesses. But you have to try all the algorithms and choose the one that yields the best performance for _your_program_! >Martin > >>And don't forget that using verified null-move pruning, you detect the zugzwangs >>and end up with the correct result, while in standard version you don't. >> >> >>>Martin
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