Author: Inmann Werner
Date: 01:59:47 10/06/99
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On October 05, 1999 at 16:10:49, Robert Hyatt wrote: >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"... But it is anyway a cutoff. (not the right word, i think) Problems can occur with hashtables, if the position is searched again with a wide open window, where -9 is a right value to accept. (or -0.30) But anyway, if I use -9, i forgot all about positional evaluation, if i use -.30 the move may be choosen without any evaluation reason, forgetting the "lost queen". For me something like a unsolvable problem, one should not think to much about, cause solving it takes to much speed, produces more problems. If I write in the hashtables "not accurate value", the entry gets senseless and coming to the position causes full research. If I write in the wrong value I have to live with it. Werner
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