Author: Dave Gomboc
Date: 00:20:27 01/18/00
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On January 13, 2000 at 08:00:31, Amir Ban wrote: >[Event "ACM 1991"] >[Site ""] >[Date ""] >[Round ""] >[White "Cray Blitz"] >[WhiteElo ""] >[Black "Deep Thought II"] >[BlackElo ""] >[Result "0-1"] > >1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 Nc6 6. f4 e5 >7. Nxc6 bxc6 8. fxe5 Ng4 9. Be2 Nxe5 10. Be3 Be7 11. O-O Be6 >12. Qd4 O-O 13. Rad1 f6 14. b3 Qe8 15. Na4 Qg6 16. Bf4 Rf7 17. Qe3 >Raf8 18. Qxa7 Qxe4 19. Bd3 Qb4 20. Qe3 Ra8 21. c3 Qb7 22. Rf2 >Qa7 23. Qxa7 Rxa7 24. Be3 Ra5 25. Bb6 Ra8 26. Bc2 Bf8 27. Re1 >c5 28. Be4 Ra6 29. Rb1 f5 30. Bc2 Rb7 31. Bd8 g6 32. Re1 c4 >33. Rb1 Bd7 34. Nb2 Ra8 35. Bg5 Rxa2 36. b4 Bb5 37. Re2 Bg7 >38. Nd1 Ra6 39. Bd2 Nd3 40. Ne3 Ra2 41. Bxd3 cxd3 42. Rf2 Rxd2 >43. Rxd2 Bxc3 44. Nf1 Bxd2 45. Nxd2 Re7 46. Nf3 h6 47. Rb2 Re4 >48. Kf2 g5 49. g3 f4 50. gxf4 Rxf4 51. Kg3 h5 52. Nd2 h4+ 53. Kg2 >Bc6+ 54. Kg1 Rg4+ 55. Kf2 Rg2+ 56. Ke3 Bb5 57. Ra2 Rxh2 58. Ra5 >Re2+ 59. Kd4 h3 60. Rxb5 Rg2 61. Rb8+ Kg7 62. Rb7+ Kg6 63. Rd7 0-1 > >The move in question is 27 ... c5. > >Black gets material advantage on move 35. So far as I can see, the reason is >white's 34'th move, that gives up a pawn for no good reason. White is already in >positional trouble before that because of the weak 32. Re1. White can play, for >example, 32. Bg5 and remain fine. If Deep Thought said +2 after 27 ... c5 it >must have been a bug. > >Amir I decided to use a little electrcity and check this out. First, here's what Crafty 17.4 says after a few hours on a 2xPII-266 for Black's 27th: depth=17 -0.20 27. ...c5 28. Be4 Ra6 29. Rb1 Re7 30. Re2 Bf7 31. Kh1 Nc4 32. Bd3 Rxe2 33. Bxe2 Ra8 34. Bc7 Ne3 35. Ra1 Nd5 36. Bb6 Nxb6 37. Nxb6 I forgot to record the move progess indicator: I assume it was stilll searching the move ...c5 on the 17th ply. I also forgot to record the node count, which might not matter, because it's a 32-bit counter and might have rolled over, for all I know. I didn't play through the PV: the main thing that's important is that Crafty doesn't see squat for Black here, this early on. So, I played through the game to move 34, where you said that White gave up a pawn for no reason, and started that going. 34. Nb2 was assessed at -1.4 or so pretty early, and was replaced by 34. Rff1. On depth 10, Rff1 was found to suck as well (-1.4) and the key move switched to 34. Rd1. As depth 14 computes, the current info is depth=14 7/35 -1.12 34. Rd1 Bh6 35. Re2 Bb5 36. Rde1 Bg7 37. Re3 f4 38. Re4 Nf7 39. Re8+ Bxe8 40. Rxe8+ Bf8 41. Bh4 cxb3 42. axb3 d5 Nodes: 350406379 (25 minutes) (the node count doesn't change every time the elapsed time and NPS are being updated... bug in Crafty or Winboard, or normal behaviour?) Anyway, the PV looks somewhat unconvincing (White basically is marking time with his rooks for a few moves while Black decides where to put his dark-squared bishop). I wouldn't be terribly surprised if Rd1 were to fail low to the -1.4 area in the next iteration or two as well. Maybe Nb2 looks like a sick move, but if Cray Blitz wasn't programmed to play the move that failed low last if the scores for all moves are found to suck relative to the score expectation when the search was started, then the reason it was played is simply that all the other moves are bad too. I didn't get to check out the move 32 area yet, but I'll get there. I want to let this search go for a while longer, because I'd like to know if the eval for 34. Rd1 will drop further or not. (Search now says depth=15 1/35 -1.12 with same PV, 558867785 nodes, 38 minutes... probably implying that the "depth 17" search above was really a depth 16 search) Dave
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