Author: Tony Werten
Date: 13:06:43 09/06/02
Go up one level in this thread
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
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