Author: Tony Werten
Date: 16:39:05 09/06/02
Go up one level in this thread
On September 06, 2002 at 18:44:22, Robert Hyatt wrote: >On September 06, 2002 at 16:26:44, Tony Werten wrote: > >>On September 06, 2002 at 16:15:25, Robert Hyatt wrote: >> >>>On September 06, 2002 at 16:06:43, Tony Werten wrote: >>> >>>>On September 06, 2002 at 16:03:06, Robert Hyatt wrote: >>>> >>>>>On September 06, 2002 at 15:46:53, Tony Werten wrote: >>>>> >>>>>>On September 06, 2002 at 14:45:11, Dann Corbit wrote: >>>>>> >>>>>>>Did anyone notice his cutoff idea in the evaluation function? >>>>>>> >>>>>>>It seems to me to be a very good idea, and I don't know if others have tried it >>>>>>>out. >>>>>>> >>>>>>>Basically, it consists of three modes with two early exits... >>>>>>> >>>>>>>1. If the material + structure score alone is dominant enough, it exits right >>>>>>>away. >>>>>>>2. Otherwise, it processes the piece list. If that score is dominant, it exits. >>>>>>>3. Otherwise, it does a full board control scan for all 64 squares. >>>>>>> >>>>>>>It is described starting on page 62 under the section "3.3.2 Multi Staged >>>>>>>Design" >>>>>>>He gets roughly 71% evals returning in stage #1, 13% in stage #2 and 7% in stage >>>>>>>#3. >>>>>>> >>>>>>>It seems like it might be a big win to do it that way. >>>>>> >>>>>>It's called lazy eval and is not a good idea. The times it is wrong happen to be >>>>>>the important ones. >>>>>> >>>>>>Tony >>>>> >>>>> >>>>>Two things... >>>>> >>>>>First, you _can_ do a lazy eval with zero error. I did it in Cray Blitz and >>>>>I explained the idea here before... >>>>> >>>>>You can compute the possible "positional error" (the amount the score will >>>>>change max and min) for each type of piece. When you do a lazy eval, you >>>>>can use this min/max and sum 'em up (or do it incrementally as we did, which >>>>>can be a headache) so that you know the "independent piece max/min scores". >>>>> >>>>>If you lazy eval based on that, you get _zero_ errors because you will _really_ >>>>>know that the individual piece scores can't produce a number larger than X or >>>>>smaller than Y, so you can make an informed decision. >>>>> >>>>>I don't do that today because each time you change the eval, you have to >>>>>update those min/max values which is something I would continually forget. >>>> >>>>Yes, correct. But when you get 71% hitrate your bounds are not very wide. >>>> >>>>> >>>>>2. You can get good results with remembering the min/max positional scores >>>>>during a real game. yes, the scores will continue to "widen" and reduce lazy >>>>>eval exits, but the error rate is not that bad. Compared to the cost. >>>> >>>>In XiniX the hitrate drops to <5% quite fast this way. IMO not really worth it. >>>> >>>>Tony >>> >>> >>>I don't see it drop that far, but I don't watch it carefully unless I am >>>suspecting trouble either... I will take a longer look. >> >>Might be better for other programs i think. My kingsafety is calculated during >>the piece evaluations as is my passed pawn score. ( to name 2 big ones ) >> >>Tony > > >Mine is actually calculated _last_ as I need to know stuff about all the >pieces first. But I just factor that into the "error window". The passed >pawn scores and stuff like trapped bishops are done early since they are >big values too. I do the trapped bishop in piece eval as well. Maybe getting it out would improve my hitrate. I'll have a look one of these months. Tony
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