Author: Joachim Rang
Date: 09:45:39 03/23/04
Go up one level in this thread
On March 23, 2004 at 12:38:29, martin fierz wrote: >On March 23, 2004 at 12:22:16, Tord Romstad wrote: > >>On March 23, 2004 at 11:31:18, martin fierz wrote: >> >>>On March 23, 2004 at 10:14:05, Tord Romstad wrote: >>> >>>>One of the really embarassing things about Gothmog's eval of this position >>>>is that it doesn't even consider the bishop on g1 to be a bad biship. My >>>>bad bishop eval is based on the number of *blocked* pawns on squares of the >>>>bishop's colour. In the position we discuss, there are only two such pawns >>>>(on e3 and g3). Therefore Gothmog thinks that the g1 bishop isn't really >>>>that bad. It has limited mobility, but it should be easy to relocate it >>>>to a better square. >>> >>>perhaps you should change your definition a bit. the pawn on f2 is virtually >>>blocked too, and the pawn on c4 is rather blocked and with it the one on c3. in >>>any case, the f2-pawn should be recognizable as blocked. >>>to evaluate my bishops, i use a sum of c1*(blocked pawns on that color) + >>>c2*(unblocked pawns on that color). i think that is a better way of doing it. >>>still it's not good, because as said, the g1-bishop would be just fine on a3 or >>>on f4. >> >>Thanks for the suggestions. You are probably right, I should have a look >>at my bad bishop code. > >an interesting idea posted here lately (don't remember by who - sorry) was to >look in the forward direction of the bishop and see whether it hits own pawns. >like this, a bishop on a3/f4 in your position gets no penalty, but a bishop on >g1 does. obviously, this criterion alone is not too useful either, but it may be >an ingredient. > >>>>As so often, Gothmog's eval proves to be the worst of them all. >>>no!!! as i said you asked the wrong question! you didn't even answer the right >>>question yourself, and all others won't answer it either as i know them... the >>>right question is: >>> >>>*************************************************************** >>>"please give me your static eval with bishop on g1, c1 and a3". >>>*************************************************************** >>> >>>my answer is "-0.49 (g1), -0.51(c1), -0.35(a3)." >> >>... and my answer is "+0.24 (g1), +0.18 (c1), +0.31 (a3)". >> >>>as you can see, my answer is always about the same, and for example ridiculous >>>in that g1 is preferred over c1 (reason: the rook's mobility is smaller for >>>Bc1). >> >>Same thing here, as you can see from my numbers. >> >>>i will bet another beer (you owe me one IIRC) >> >>I do. :-) >> >>>that most of the people who >>>answered your post (and of who you think they are evaluating this better) have >>>similar problems. e.g. the position with the bishop on c1/a3 is roughly equal >>>(well, with the Ba3 you in fact immediately win a pawn, but just philosophically >>>speaking, white has little to fear with a pawn for the exchange and the bishop >>>pair) and all those guys who gave a big negative score for white will still be >>>giving a big negative score for white (because nobody is realizing that the >>>g1-bishop is the big problem, they just think exchange=2 pawns), and gothmog's >>>eval will be the superior one. >> >>Do you think that white has the advantage with the bishop at c1? > >no. i think the position is equal. there is nothing black can do do improve as >far as i can see; i.e. there are 3 things he can try: >-> return the exchange by capturing c4 at some point >-> play d5 at some point >-> play a6-b5 at some point > >i don't believe in the pawn breaks, you remove white's weak pawn on c4, open up >the position for the bishops and still have no clear plan. that leaves the first >possibility, but then it's not too clear either. specially if you already have >the bishop on a3 black must also look out for his own weakness on d6. so i think >black does best doing nothing, and white has no active plan either that i can >see, so it's a draw. > >i thought you were unhappy with your evaluation because you were +0.2 while >others were -1.0, which is of course looking bad for you when you have the >bishop on g1, then the others are much better. but with the bishop on c1, the >correct eval is probably about 0, and then your +0.2 are better than the -1.0 of >the others. that's why i said you should be feeling better now. not about the >position with the bishop on g1 of course, but in general - gothmog seems to be >closer to the truth (according to me) than the others. > Shredder 8 manages both: it gives -0.2 for the bishop on c1 and -1.4 for the bishop on g1. Don't ask me how SMK has solved this. regards Joachim >cheers > martin > > >PS: >>Exchange=1.75 pawns in Gothmog, by the way. >better than 2.0 :-)
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