Author: Robert Hyatt
Date: 13:10:49 10/05/99
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On October 05, 1999 at 15:32:02, Inmann Werner wrote: >On October 05, 1999 at 10:40:49, Robert Hyatt wrote: > >>On October 05, 1999 at 05:25:21, Bas Hamstra wrote: >> >>>What are good ways to cut down the number of evals? I saw Bob Hyatt post that he >>>could easily double NPS when using "Lazy Eval". >>> >>>What is a correct way to do that? Is there more to it than the qsearch "delta" >>>type of pruning? >>> >>> >>>Regards, >>>Bas Hamstra. >> >> >>The idea is that in general, your eval _must_ return scores > alpha and >>< beta, or they are not useful, correct? (please ignore this if you use >>mtd(f) of course, as it is more complicated then). Suppose alpha=-.30 and >>beta=+.30. When you get into your eval, if you can figure out that you >>can't possible bring the score within that window, you can return the >>appropriate bound quickly. IE if you come in and material is at -9.00 (You >>have lost a queen somewhere in this path) then do you have an eval term that >>can add +9.00 to the score to bring it inside the window? If not, you can >>either return -9.00, or the more safe -.30, since the score is at least >>that bad. >> >>You can use this at several points to bail out after you are sure you can't >>get "in the box" with the score... > >why is giving back -0.30 a more safe way then returning the material_balance of >-9.00, what I do now? > >Werner Question is, "which is closer to the right value?" for some positions, your -9 is closer. For others, the -.030 might be closer (ie if the -9 can be offset by an unstoppable pawn, for example...) I prefer to be 'conservative here' as I will remember that -9 and it might be overstated... I'd rather guess "score is < -.30" than "score is < -9.00"...
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