Author: Uri Blass
Date: 03:00:12 05/01/04
Go up one level in this thread
On May 01, 2004 at 00:12:43, Robert Hyatt wrote: >On May 01, 2004 at 00:03:41, Andrew Wagner wrote: > >>On April 30, 2004 at 23:47:06, Robert Hyatt wrote: >> >>>On April 30, 2004 at 23:26:55, Andrew Wagner wrote: >>> >>>>[snip] >>>>> >>>>>Black is already winning in position 2: >>>>> >>>> >>>>Right, I just meant the sac was losing, not the position. In fact, the first >>>>position is also winning without the sac, quite easily. My point with the second >>>>position was that where in the first position the two connected passed pawns >>>>made up for the difference of the rook, in the second position they weren't. I'm >>>>thinking it would be tricky to create a non-expensive eval term for such a >>>>complicated static evaluation. I mean, a human can look at it and quickly see >>>>"the king's not close enough", but that's not so easy for a computer to see >>>>without calculating. >>> >> >>Hmm? You can't be doing too much with it if you're not solving this until 13 >>ply. > > >Look at the position _carefully_. This is a _one_ tempo position. One white >pawn prevents the white king from being able to stop the two connected black >pawns. I am conservative there. Move the king one file toward the h file and >you get this: > 10 0.14 -2.54 1. ... c3 2. bxc3 Rxc3 3. Ra2 Rc2 4. > Ra1 Re2 5. Rd1 Rxe3+ 6. Kf2 Rh3 7. > Ke1 > 10-> 0.20 -2.54 1. ... c3 2. bxc3 Rxc3 3. Ra2 Rc2 4. > Ra1 Re2 5. Rd1 Rxe3+ 6. Kf2 Rh3 7. > Ke1 (s=2) > 11 0.26 -2.58 1. ... c3 2. bxc3 Rxc3 3. Ra2 Rc2 4. > Ra1 Re2 5. Kf3 Rxh2 6. Rd1 Rh3+ 7. > Kf2 Rh2+ 8. Kf3 > 11-> 0.51 -2.58 1. ... c3 2. bxc3 Rxc3 3. Ra2 Rc2 4. > Ra1 Re2 5. Kf3 Rxh2 6. Rd1 Rh3+ 7. > Kf2 Rh2+ 8. Kf3 (s=3) > 12 0.68 -2.37 1. ... c3 2. bxc3 Rxc3 3. Kh4 Rxa3 > 4. Kh5 Ke6 5. Kg5 Rc3 6. Kh6 Kd5 7. > Kxh7 a3 (s=2) > 12 0.91 +1 1. ... Rxb2!! > 12 1.19 -3.61 1. ... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kc5 6. Rb8 d2 7. > > >Finds it one ply quicker. But the problem here is the threat of repetition by >white. Takes a bit of a search to see that the black king finally escapes all >the rook checks. > >Move the white king to the h-file and you get this: > > 11 0.30 +1 1. ... Rxb2!! > 11 0.39 -3.52 1. ... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kc5 6. Rb7 d2 7. > Rxh7 Kd6 8. Rf7 d1=Q 9. Rxf5 (s=12) > 11-> 0.47 -3.52 1. ... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kc5 6. Rb7 d2 7. > Rxh7 Kd6 8. Rf7 d1=Q 9. Rxf5 (s=2) > 12 0.66 -3.79 1. ... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kc5 6. Rb8 d2 7. > Rc8+ Kb6 8. Rd8 c2 9. Rxd2 c1=Q 10. > Rd3 > 12-> 0.91 -3.79 1. ... Rxb2 2. Rxb2 c3 3. Rb6+ Ke7 > 4. Rb7+ Kd6 5. Rb6+ Kc5 6. Rb8 d2 7. > Rc8+ Kb6 8. Rd8 c2 9. Rxd2 c1=Q 10. > Rd3 > >So you can get the idea. The white pawn at e3 is the key here. Remove it and >move it to g3: > > 12-> 1.95 -1.77 1. ... Ke6 2. Ke3 Kd5 3. h3 h5 4. Rf2 > d2+ 5. Kxd2 Rxb2+ 6. Ke1 c3 7. Re2 > c2 8. Re5+ Kd4 9. Kd2 (s=2) > 13 2.54 -1.83 1. ... Ke6 2. Ke3 Kd5 3. h3 h5 4. h4 > Rb6 5. Kf2 Re6 6. Kg2 Ke4 7. Kf2 Re7 > 13-> 3.27 -1.83 1. ... Ke6 2. Ke3 Kd5 3. h3 h5 4. h4 > Rb6 5. Kf2 Re6 6. Kg2 Ke4 7. Kf2 Re7 > (s=2) > 14 7.31 -1 1. ... Ke6 > 14 11.82 -1.42 1. ... Ke6 2. h3 c3 3. bxc3 Rxc3 4. > Ke3 Rxa3 5. Rxd3 Rb3 6. Kd4 h5 7. Rd2 > a3 8. Re2+ Kd6 9. Rg2 > 14-> 14.96 -1.42 1. ... Ke6 2. h3 c3 3. bxc3 Rxc3 4. > Ke3 Rxa3 5. Rxd3 Rb3 6. Kd4 h5 7. Rd2 > a3 8. Re2+ Kd6 9. Rg2 > > >The sac doesn't work. That is why this is _really_ a tactical problem, not an >evaluation problem... I do not see it as a proof that it is a tactical problem because evaluation function can consider also the pawn at e3 Uri
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