Author: Uri Blass
Date: 08:14:49 02/25/04
Go up one level in this thread
On February 25, 2004 at 10:52:27, Robert Hyatt wrote: >On February 25, 2004 at 05:56:16, martin fierz wrote: > >>On February 24, 2004 at 11:25:23, Robert Hyatt wrote: >> >>>On February 24, 2004 at 11:17:32, martin fierz 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. :) >>>> >>>>hehe, i never claimed i wanted 100%. i think your score should reflect the >>>>amount of certainty you have. >>>> >>>>>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. >>>> >>>>nope. your rule "connected passers are strong when there are many pieces, >>>>separated passers when there are few pieces" is good in some cases. but it is >>>>not good in quite a lot of cases IMO, with no disrespect to your GM friend. if i >>>>make a more accurate version of that rule, i will beat you when it comes up :-) >>>> >>> >>>Perhaps you misunderstood my idea. Connected passers are better when there are >>>any pieces on the board. But split passers are better when there are none. I >>>just have a smooth transition from one to the other to avoid yet another problem >>>called "an evaluation discontinuity".. >> >>yes, in this case i misunderstood, but i think my misunderstanding is better >>than your understanding :-) >>connected passers are better with many pieces, split passers are better against >>*some* pieces. and of course when there are no pieces left. split passers which >>are one file apart are worse than connected passers usually. it all depends on a >>lot more than just a one-line-rule... > >I don't usually do "one line rules". > >First, I don't agree with the first part of your statement. I don't think split >passers are better than connected passers with "some pieces" on the board. I >just think they are better as pieces come off. I think it is depended on the position and there are good chances that they are better with some pieces on the board. [D]3nk3/8/8/P6P/3pp3/8/8/3NK3 w - - 0 1 The split passers are better. [D]8/8/8/7P/8/8/P6b/4K2k b - - 0 3 bishop cannot stop split passed pawns. [D]8/8/8/7P/6P1/8/7b/4K2k b - - 0 3 bishop draw against connected passed pawns. Uri
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