Author: Robert Hyatt
Date: 07:11:42 09/07/02
Go up one level in this thread
On September 07, 2002 at 04:12:17, Dave Gomboc wrote: >On September 06, 2002 at 21:27:36, Robert Hyatt wrote: > >>On September 06, 2002 at 20:43:55, Dave Gomboc 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. >>> >>>Not big enough, judging from that bishop on a8 in the other thread. <grin> >>> >>>Dave >> >> >>Wrong bishop idea. :) >> >>I am talking about white playing Bxa7 and black playing b6 which traps the >>bishop. :) > >What's the difference? You're down a piece either way. One just stays on the >board a while longer! > >Dave One is probably going to be lost. The other might one day see light again, although in _that_ position probably not. But even then it might help defend a weak pawn and act like a "tall pawn"... But the a8 bishop was bad of course...
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