On 10 avr. 09, at 11:52, Alexander Wagner wrote: > Hi! > > Except the pretty technical discussion that follows, those > who just like chess might go to the end, copy the PGN > notation to clipboard and then go Tools / Import one PGN > game and enjoy. ;) > > As I just stumbled upon this very nice study below, I also > found it is a demonstration why annotating backwards really > leads to a more correct evaluation of the positions. We had > this discussion recently, but this example in particular > seems a very strong usecase, as the effect is very large. > (An evaluation difference between forward and backward of > 0.01 might not show it that strongly. > > Starting out at > > 6N1/3P3k/n2K3p/2p3n1/1b6/2p1p1P1/8/3B4 w - - 0 1 > > Given the initial position, Shredder 11 evaluates it with -3.5 > at depth 16, while Rybka 2.2n (the free one) gives even > -4.3 at this level. Their best line is, and they agree on this, > > 1.Nf6+ Kg7 2.Nh5+ Kg6 3.Nf4+ Kf5 4.Nd5 Ke4 5.Bh5 Ba5 6.Nxc3+
For your information, at fixed depth 16, HIARCS 12.1 MP on a Mac evaluates at -5.84 1.Nf6+ Kg7 2.Nh5+ Kg6 3.Nf4+ Kf5 4.Kc6 Nb8 5.Kc7 Nxd7 > Note: the study is white to move an WIN. The evaluation at > this point is, however, 3.5 in favour of Black! The initial > moves of this line are correct, both engines fail to find > the key move 3.Bc3+!!. Lets point them with the nose to that > one. After 3.Bc3+ I get on depth 16 from Shredder > > -9.99 3.... Kxh5 4.Bd1+ Kg6 5.Ke5 Nf7+ 6.Kf4 Nb8 7.d8=B Nxd8 > 8.Kxe3 Kg5 9.Bc2 Kg4 10.Kf2 c4 11.Bd1+ Kh3 12.Bc2 Kg4 > 13.Bd1+ Kh3 14.Bc2 Kg4 > > and Rybka tells me something like > > -9.76 3.... Kxh5 4.Bd1+ HIARCS says (after 3.Bc2+ not Bc3 :-) +2.07 after 3... Kxh5 4.d8=Q Kg4 5.Kc6 Nf3 6.Qg8 Kh3 7.Qe6 Kg2 8.Qxe3 Nd4 9.Kb7 Nxc2 10.Qe4 Kxg3 11.Qd3 Kf4 12.Qxc2 Nb8 13.Kxb8 h5 > So we're now at 9.x in favour of Black. Still, White has to > win... > > Both don't like the Queen sacrifice 4.d8=Q. Again pointing > them with the nose to it... After this move the two differ > quite a bit. > > Shredder: > -13.34 4.... Nf7+ 5.Ke6 Nxd8+ 6.Kf5 e2 7.Be4 e1=N 8.Bd5 c2 9.Bc4 > c1=N > > Rybka: > +4.69 4.... Kg4 5.Kc6 Kxg3 6.Qd6+ Kg4 7.Qd3 Kf3 8.Bd1+ HIARCS says +2.74 4… Kg4 5.Qe8 c4 6.Kc6 Ba3 7.Bd1 Kh3 8.Qxe3 Nb4 9.Kb5 Now if I start the program again (allowing it to forget its previous work) and don't limit the depth to 16 (the moves you give go to 21 plies!) I get at 21 plies: +2.75 1.Nf6, it took a while though (around 3 billion nodes). --- Do you know this following position? 3b3r/4k3/rp3p1p/pPp1pPpP/P1PpP1P1/3P4/1K6/8 w - - 0 1 HIARCS, at first, wants to take the "free" rook and suicide. Any human will only move it's king and it's a draw. After a short time HIARCS will finally choose 1.Kc2 and the score will be -24.06 !!! Morality: don't rely too much on computers assessments :-) Charly ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Scid-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/scid-users
