Author: Robert Hyatt
Date: 15:44:22 09/06/02
Go up one level in this thread
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.
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