Author: blass uri
Date: 20:39:06 05/17/00
Go up one level in this thread
On May 17, 2000 at 19:20:40, Ernst A. Heinz wrote:
>Hi Bob,
>
>>I think playing Bxa7 very quickly is a bug. Because you are right, trapping
>>the bishop is easy, and breaking the trap is deep. For every game you win by
>>playing Bxa7 you will lose 10.
>
>Calling this a "bug" is a bold conjecture IMO -- your observations
>above might be true for blitz games but they certainly do not hold
>for longer time controls according to my experience.
I agree that this is not a bug because the decision to let Bxa7 was a design
decision but it is not clear that this decision was correct.
This is a position from the game Junior5.4-Crafty16.6
[D]r2nkb1r/pp1n2pp/8/1P1pp3/8/2P1B3/1P3PPP/RN2KB1R w KQkq - 0 1
Junior played the move 17.Rxa7 and was in trouble after Rxa7 18.Bxa7 b6
Junior saved a draw because of the fact that crafty did not use tablebases so
Junior could escape to a KR vs KRN endgame.
I do not think that Rxa7 is a good move
The game was played with p200 under Junior5 interface(engine-engine game).
Can your program avoid Rxa7?
Here is the game
[Event "120/40+60/20+30/game"]
[Site "?"]
[Date "1999.04.04"]
[Round "1"]
[White "Junior 5.4"]
[Black "Crafty 16.6"]
[Result "1/2-1/2"]
[ECO "D02"]
[Annotator "Uri"]
[PlyCount "204"]
[EventDate "1999.04.02"]
{131071kB, Jun-book.ctg. K6-2-350} 1. d4 {0} 1... d5 {2} 2. Nf3 {0} 2... Nf6 {2
} 3. Bf4 {0} 3... c5 {2} 4. e3 {0} 4... Nc6 {2} 5. c3 {0} 5... Qb6 6. Qb3 {
0.15/15 254} 6... Qxb3 {0.28/11 213} 7. axb3 {0.23/15 103} 7... cxd4 {
0.27/11 260} 8. exd4 {0.27/15 165} 8... e6 {(Bf5) 0.27/12 204} 9. b4 {
(Be2) 0.34/17 208} 9... Bd7 {(Be7) 0.38/12 376} 10. Ne5 {(Be2) 0.39/17 352}
10... Nh5 {0.45/12 222} 11. Be3 {0.45/16 203} 11... Nf6 {0.51/12 200} 12. Nxd7
{0.40/16 219} 12... Nxd7 {0.46/13 198} 13. Bf4 {(Be2) 0.39/17 152} 13... f6 {
0.54/12 198} 14. b5 {(Be2) 0.33/16 243} 14... Nd8 {(Ne7) 0.59/12 198} 15. Be3 {
(Bc7) 0.35/16 175} 15... e5 {(Bd6) 0.40/12 198} 16. dxe5 {(Be2) 0.46/17 379}
16... fxe5 {0.35/12 202} 17. Rxa7 {(b6) 0.58/17 155} 17... Rxa7 {0.16/13 197}
18. Bxa7 {0.57/16 62} 18... b6 {0.15/12 197} 19. g3 {0.54/17 211} 19... Ne6 {
0.21/13 198} 20. Bg2 {0.62/15 136} 20... e4 {0.44/12 213} 21. Nd2 {
(f3) 0.53/16 308} 21... Bc5 {(Bd6) -0.17/11 201} 22. Nb3 {(Ke2) 0.52/16 268}
22... Ke7 {(Rf8) -0.16/11 206} 23. Ke2 {0.49/16 245} 23... Rf8 {-0.22/12 196}
24. Rf1 {0.55/15 143} 24... Ra8 {(Kd6) -0.03/11 203} 25. Ra1 {0.39/16 238}
25... Rf8 {0.00/11 197} 26. Nxc5 {(Rf1) 0.39/14 138} 26... Nexc5 {-0.06/13 195}
27. f3 {(b4) 0.40/15 172} 27... Rf5 {(Kd6) -0.24/11 214} 28. fxe4 {0.67/15 211}
28... Nxe4 {-0.11/12 194} 29. Bxe4 {(Bh3) 0.72/16 342} 29... Re5 {
(dxe4) -0.13/13 198} 30. Ra6 {(Ra4) 0.76/16 286} 30... Rxe4+ {
(Re6) -0.47/14 198} 31. Kd2 {(Kd3) 0.78/16 292} 31... Re6 {-0.30/14 197} 32. b4
{(Kd3) 0.69/17 124} 32... Kd8 {(Kf6) -0.80/13 192} 33. Kd3 {0.39/18 144} 33...
Kc7 {-0.79/15 194} 34. g4 {(h3) 0.00/15 119} 34... g5 {(Ne5+) -0.99/14 192} 35.
h3 {(Kd4) -0.43/17 108} 35... Rh6 {-1.48/15 192} 36. Kd4 {-0.92/19 451} 36...
Rxh3 {-1.84/15 192} 37. Ra4 {(Bxb6+) -0.84/17 240} 37... Rg3 {-2.14/14 192} 38.
Ra6 {-1.11/16 103} 38... h6 {-2.18/14 192} 39. Kxd5 {-1.31/16 110} 39... Rxc3 {
-2.67/14 191} 40. Ra1 {(Ra2) -1.57/16 104} 40... Rd3+ {(Rg3) -2.81/14 96} 41.
Ke4 {-1.66/17 140} 41... Rd2 {(Rb3) -2.89/14 185} 42. Kf5 {(Rc1+) -1.73/16 272}
42... Rd5+ {-3.04/14 185} 43. Kg6 {-1.90/17 201} 43... Ne5+ {-3.46/15 185} 44.
Kxh6 {-2.03/16 153} 44... Nxg4+ {-3.54/15 185} 45. Kh5 {-2.10/16 159} 45...
Nf6+ {-3.58/14 187} 46. Kg6 {(Kh6) -2.12/17 160} 46... Nd7 {-3.31/14 377} 47.
Rg1 {(Kf7) -2.53/17 673} 47... g4 {-3.87/14 222} 48. Kf7 {-2.58/16 127} 48...
Rd4 {(Rxb5) -4.45/14 171} 49. Kg6 {(Ke6) -2.20/16 279} 49... Rxb4 {
(Ne5+) -4.50/14 168} 50. Kf5 {-1.59/15 122} 50... Rxb5+ {(Kb7) -4.55/14 166}
51. Kxg4 {-0.54/14 121} 51... Ra5 {(Rb4+) -4.55/14 167} 52. Bxb6+ {
(Rc1+) -0.54/17 129} 52... Nxb6 {-4.60/14 166} 53. Kf4 {(Kf3) -0.55/17 104}
53... Nd5+ {(Kd6) -4.60/12 166} 54. Ke5 {(Kf5) -0.58/17 111} 54... Nc3+ {
-4.60/12 220} 55. Ke6 {-0.64/18 117} 55... Ne2 {-4.60/12 169} 56. Rg4 {
(Rd1) -0.69/18 182} 56... Rc5 {-4.60/13 205} 57. Re4 {-0.71/18 146} 57... Nc3 {
(Rc6+) -4.60/14 143} 58. Rd4 {(Rg4) -0.71/19 185} 58... Kc6 {
(Rc6+) -4.60/13 155} 59. Rd6+ {(Kf6) -0.72/19 130} 59... Kb7 {
(Kb5) -4.60/14 137} 60. Rd7+ {(Rd4) -0.70/18 97} 60... Kc8 {(Kb6) -4.60/13 69}
61. Ra7 {(Rd3) -0.62/17 51} 61... Rh5 {(Rc4) -4.60/12 54} 62. Ra1 {
(Rg7) -0.61/16 40} 62... Kd8 {(Rh6+) -4.60/11 52} 63. Ra7 {(Rg1) -0.68/16 51}
63... Nb5 {(Rh6+) -4.65/12 51} 64. Rd7+ {(Ra8+) -0.60/16 49} 64... Kc8 {
-4.60/14 49} 65. Rf7 {(Rd2) -0.56/15 56} 65... Nc7+ {(Rh6+) -4.60/11 50} 66.
Kd6 {-0.49/16 48} 66... Kb8 {(Rh6+) -4.60/12 46} 67. Rd7 {(Kc6) -0.44/16 40}
67... Rg5 {(Rh6+) -4.55/12 45} 68. Kc6 {-0.41/17 36} 68... Rg6+ {
(Rg8) -4.45/12 54} 69. Rd6 {-0.30/17 31} 69... Rg8 {-4.50/13 42} 70. Rd1 {
(Rd7) -0.33/16 42} 70... Kc8 {(Ne6) -4.50/11 42} 71. Rc1 {(Rf1) -0.36/16 70}
71... Rg5 {(Rg6+) -4.55/11 75} 72. Kb6 {(Rf1) -0.32/16 31} 72... Rb5+ {
(Rg6+) -4.55/12 38} 73. Kc6 {-0.45/16 12} 73... Ra5 {(Rh5) -4.55/12 38} 74. Rh1
{(Kb6) -0.31/15 34} 74... Ne6 {(Ra6+) -4.60/11 43} 75. Kd6 {-0.30/16 89} 75...
Nf4 {(Nd8) -4.55/11 34} 76. Rc1+ {-0.33/14 33} 76... Kd8 {-4.55/12 33} 77. Rd1
{(Rc5) -0.28/16 39} 77... Ng6 {(Nh5) -4.55/11 32} 78. Rc1 {(Rd5) -0.47/14 24}
78... Nh4 {-4.55/11 34} 79. Rd1 {(Rc5) -0.35/15 34} 79... Ra6+ {-4.55/11 31}
80. Ke5+ {-0.52/14 45} 80... Ke7 {-4.55/12 31} 81. Rd3 {(Ke4) -0.48/14 22}
81... Re6+ {(Ng6+) -4.60/11 29} 82. Kf4 {(Kd5) -0.55/16 88} 82... Ng6+ {
(Kf6) -4.60/11 28} 83. Kg5 {(Kg3) -0.41/17 24} 83... Kf7 {(Nh8) -4.60/11 27}
84. Rd5 {(Rd7+) -0.39/16 27} 84... Re4 {(Ne7) -4.65/11 27} 85. Rf5+ {
-0.35/16 22} 85... Kg7 {-4.65/13 26} 86. Rd5 {(Rf2) -0.36/17 34} 86... Ne7 {
-4.65/12 25} 87. Rd6 {-0.26/15 22} 87... Rc4 {(Re5+) -4.60/11 27} 88. Rd2 {
(Re6) -0.28/14 23} 88... Rb4 {(Rc7) -4.65/11 23} 89. Rd3 {(Rg2) -0.30/16 46}
89... Kf7 {(Rb5+) -4.65/11 27} 90. Rd6 {(Rf3+) -0.33/14 15} 90... Nc8 {
(Rb5+) -4.60/11 23} 91. Rf6+ {(Rh6) -0.37/14 18} 91... Ke7 {-4.60/12 21} 92.
Rf4 {-0.44/15 20} 92... Rb1 {-4.65/12 21} 93. Re4+ {(Rf2) -0.45/15 28} 93...
Kd6 {(Kf7) -4.65/12 20} 94. Kf4 {(Kg4) -0.44/14 15} 94... Nb6 {
(Ne7) -4.65/11 21} 95. Ke3 {(Kg5) -0.46/14 18} 95... Nd5+ {(Ra1) -4.65/10 19}
96. Kd3 {-0.36/13 19} 96... Rb3+ {(Ra1) -4.60/10 20} 97. Kc4 {(Kd4) -0.17/14 16
} 97... Ra3 {(Rb4+) -4.55/11 24} 98. Re8 {(Kd4) 0.00/15 19} 98... Nf4 {
(Ra4+) 0.00/10 21} 99. Rd8+ {(Rc8) 0.00/18 12} 99... Ke7 {(Ke5) 0.00/14 18}
100. Rh8 {0.00/20 23} 100... Kd6 {(Ra4+) 0.00/14 16} 101. Rd8+ {0.00/29 12}
101... Ke5 {0.00/60 1} 102. Rd1 {(Re8+) 0.00/61 3} 102... Ne2 {0.00/60 0}
1/2-1/2
>
>I prefer the approach of adding as little evaluation code for
>special situations as possible. The "trapped Bishop" should
>certainly get punished for losing most of its mobility. And
>the potential necessity to defend the piece will punish its
>side further. So why do we need special code for this?
I also think that a generalization of the Bxa7 trap may be better because there
are positions when the bishop is trapped in other places of the board and there
are position when a bad bishop that almost cannot move is not enough
compensation for a pawn.
a7,h7 are the most common places but I saw also a case when the bishop was
trapped on h6 by the pawns f6,g5 and there are cases when the bishop is not
trapped but is bad in other places of the board and cannot participate in the
game.
>
>Moreover, the alleged "trap" often turns out to be a "fata
>morgana" of human players who fear it without any good reason.
>Hence, you may rob your program of many potential chances
>if you severly punish "trapped Bishops" statically.
If it is a "fata morgana" you can find by search in most of the cases that it is
a "fata morgana" because you find that the bishop can escape from the trap.
Uri
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