Author: Heiner Marxen
Date: 14:02:34 01/08/02
Go up one level in this thread
On January 07, 2002 at 22:35:17, Robert Basham wrote:
>[D]2kr1b1r/1pp1qp1p/3p2p1/1P1Pp3/2Q1P1n1/R4N2/1PP2PPP/5RK1 w - -
>
>Some computor programs miss this mate in 4..!
That is funny. Here is the complete solution tree from Chest (0.21 seconds):
Qc6 Kb8 Rfa1 bxc6 bxc6 Rc8 Ra8#
Rb3#
-*- Ra8#
dxc6 =*= Ra8#
b6 Qa8#
Ra8#
-*- Ra8#
bxc6 bxc6 Kb8 Rfa1 Rc8 Ra8#
Rb3#
-*- Ra8#
-*- Ra8#
dxc6 Kb8 Rfa1 =*= Ra8#
-*- Ra8#
-*- Ra8#
I don't see anything special here. Crafty (18.10) finds it:
White(1): setboard 2kr1b1r/1pp1qp1p/3p2p1/1P1Pp3/2Q1P1n1/R4N2/1PP2PPP/5RK1 w -
-White(1): go
clearing hash tables
time surplus 0.00 time limit 1:00 (1:00)
nss depth time score variation (1)
5 0.83 0.59 1. b6 Bh6 2. Ra8+ Kd7 3. Qb5+ c6 4.
dxc6+ Ke6 5. Qd5+ Kf6 6. cxb7 Kg7
5-> 0.88 0.59 1. b6 Bh6 2. Ra8+ Kd7 3. Qb5+ c6 4.
dxc6+ Ke6 5. Qd5+ Kf6 6. cxb7 Kg7
6 1.46 0.80 1. b6 Bg7 2. Ra8+ Kd7 3. Qb5+ c6 4.
dxc6+ Ke6 5. Qd5+ Kf6 6. cxb7 Rb8 7.
Ra7
6-> 1.66 0.80 1. b6 Bg7 2. Ra8+ Kd7 3. Qb5+ c6 4.
dxc6+ Ke6 5. Qd5+ Kf6 6. cxb7 Rb8 7.
Ra7
7 4.79 0.75 1. b6 Bh6 2. Rfa1 Rhf8 3. Ra8+ Kd7
4. Qb5+ c6 5. dxc6+ Ke6 6. Qd5+ Kf6
7. cxb7 Kg7
7 5.67 ++ 1. Qc6!!
7 5.77 Mat04 1. Qc6 bxc6 2. dxc6 Kb8 3. Rfa1 Bh6
4. Ra8#
7-> 5.86 Mat04 1. Qc6 bxc6 2. dxc6 Kb8 3. Rfa1 Bh6
4. Ra8#
time=5.86 cpu=49% mat=-2 n=841970 fh=94% nps=143k
ext-> chk=37290 cap=7045 pp=6100 1rep=5409 mate=560
predicted=0 nodes=841970 evals=87406
endgame tablebase-> probes done=0 successful=0
mate in 4 moves.
Which programs miss it? Any idea, why? Unsound forward pruning?
Cheers,
Heiner
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