Author: Robert Hyatt
Date: 18:28:19 09/06/02
Go up one level in this thread
On September 06, 2002 at 19:39:05, Tony Werten wrote: >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 I moved it out for that reason, in fact...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.