Author: martin fierz
Date: 08:19:53 02/24/04
Go up one level in this thread
On February 24, 2004 at 11:12:57, Bob Durrett wrote: >On February 24, 2004 at 11:06:00, Robert Hyatt wrote: > >>On February 24, 2004 at 10:37:21, martin fierz wrote: >> >>>On February 24, 2004 at 10:19:51, Anthony Cozzie wrote: >>> >>>>On February 24, 2004 at 09:32:08, martin fierz wrote: >>>> >>>>>On February 23, 2004 at 23:05:58, Robert Hyatt wrote: >>>>> >>>>>>On February 23, 2004 at 18:52:36, Geoff Westwood wrote: >>>>>> >>>>>>>Hi >>>>>>> >>>>>>>I was perusing the latest table of results, Crafty's static eval of 2 of the >>>>>>>passed pawn positions were interesting. >>>>>>> >>>>>>>Assuming I havent made a mistake in the cutting and pasting >>>>>>> >>>>>>>Position 1 >>>>>>>8/4k3/8/7P/1P6/3p4/4p3/4K3 b - -; id "PP-00004" >>>>>>> >>>>>>>[D]8/4k3/8/7P/1P6/3p4/4p3/4K3 b - - >>>>>>> >>>>>>>Crafty reckons this is +4.8 (good for white). This is rather clever as although >>>>>>>the black king could catch either of the white passed pawns, it cannot stop >>>>>>>both. Also blacks 2 advanced pawns cant do anything as the white king gobbles >>>>>>>them up easily. Only Crafty and Tinker understand this position statically. Any >>>>>>>tips on what the algorithm is to sort this one out ? >>>>>> >>>>>> >>>>>>This is the idea I have reported here before, pointed out (demanded to be fixed >>>>>>in fact) by a GM friend of mine. The idea is that the two separated pawns are >>>>>>better than the two connected passers. The king stops the two connected passers >>>>>>easily until the enemy king supports them, meanwhile the split passers walk on >>>>>>in... >>>>> >>>>>i don't like the generality of your statemtent here, but - it is a small price >>>>>to pay if it's right in most cases. which perhaps is the case. anyway, here's my >>>>>question: >>>>> >>>>>what does your static eval say for the black king on e6/e5/e4/e3 ? i wouldn't be >>>>>surprised if it got it wrong in some cases now... >>>>> >>>>>cheers >>>>> martin >>>> >>>>The question is always "what do you put in the search, what do you put in the >>>>eval" <shrug>. >>> >>>sort of - for me the answer is clear. the point i wanted to make (not the first >>>time, BTW) is that returning huge evaluations in positions like this may not be >>>a good idea because they are *very* sensitive to details like king position. >>>e.g. if i got it right, then it's a white win with the king on e6, but a black >>>win with the king on e5. do you really want to allow your static eval to return >>>a white win when it might be a black win? >>>of course you can say that if you get it right 60% of the time, it is better >>>than returning an equal eval in this kind of position. but wouldn't it be better >>>then to return something like +- 1 so that you never blunder into this when you >>>are e.g. a piece up and see this type of transition? >>>i generally try to return huge evals only when i am very certain that they are >>>correct. >>> >>>cheers >>> martin >> >>You are looking at this the wrong way. If you want 100% accuracy, you will die >>from it. :) >> >>If you don't do what I do, you will like connected passers, and in 90% of the >>games I will beat you when that comes up. Do you want to be right 100% of the >>cases you recognize, leaving 95% as "unclear and probably lost" or do you want >>to be right in 90% of the total cases? >> >>I choose the latter... >> >>No doubt it can be made more accurate. But no doubt that without it, it is even >>less accurate... > >Why not get rid of bugs when you know about them? > >Bob D. > it's not a bug, it's a feature. bob knows what he's doing, and believes it's the right thing to do. having a simple evaluation function which gets it right most of the time can be better than having a complex evaluation function which gets it right more often, but slows you down. it's the usual tradeoff between speed and knowledge. cheers martin > >> >> >>> >>>>I have considered trying to do a really good KP eval; at the moment it is on the >>>>back-burner but I might return to it someday. >>>> >>>>anthony
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