Author: Robert Hyatt
Date: 20:05:48 03/06/04
Go up one level in this thread
On March 06, 2004 at 17:06:23, GeoffW wrote:
>Hi
>
>Here is a position I found interesting, white has just played Rf6, black to move
>
>[D]r3qnk1/rb2bppp/4pR2/pp1pP1PP/2pP3N/P1P1P1Q1/1PB5/4B1RK b - - 0 1
>
>My programs analysis for this position is horrid
>
>Ply Eval Time Nodes Principle Variation
> 1 433 0 17 g7f6 e5f6
> 2 433 0 290 g7f6 e5f6
> 3- 393 1 4782 g7f6
> 3 204 1 8053 e7a3 b2a3 g7f6 e5f6
> 4 204 3 18575 e7a3 b2a3 g7f6 e5f6
> 5 204 6 44876 e7f6 g5f6 g7g6 h4f3 f8d7 h5g6 h7g6
> 6 192 10 97670 e7f6 e5f6 g7g6 h5g6 h7g6 h4f3
> 7 194 21 193103 e7f6 e5f6 g7g6 h4f3 a8d8 h5g6 h7g6
> 8 187 60 564304 e7f6 e5f6 g7g6 h4f3 g6h5 g3h4 f8d7 h4h5
> 9 188 132 1263805 e7f6 e5f6 g7g6 h4f3 f8d7 e1d2 a8b8 g3h2 e8d8
>10 176 396 3783030 e7f6 e5f6 g7g6 h4f3 f8d7 g3h2 a8d8 e1g3 d7b6 f3e5
>11 176 942 8062241 e7f6 e5f6 g7g6 h4f3 e8c6 g3h2 f8d7 e1g3 a8d8 f3e5
>d7e5 g3e5
>12- 136 3984 35236639 e7f6
>12 102 144954 868931003 b5b4 a3b4 a5b4 f6f4 a7a2 g3g2 b4b3 c2b1 a2a1 e1d2
>f8d7 e3e4
>
>It firstly thinks it has won a rook by taking it with Pxf6, then it realises
>this is bad, and avoids the Rook sacrifice by coming up with its own weird
>bishop sacrifice Bxa3. Two plies later then decides it had better take the rook
>after all with the obvious looking Bxf6. It takes 40 seconds to get to ply 12
>before it realises that this is also a hopeless losing move.
>Then it takes almost 25 minutes to resolve the fail low with a branching factor
>of 24 !!
>I am not sure why it struggles to resolve this specific fail low so badly, this
>is probably the trickiest fail low I have seen so far, at least for my program.
>It was taking so long I was convinced it was locking up in an infinite search
>bug. I guess it probably isnt a bug as it finally does come up with a reasonable
>move, all be it far too late.
>
>What do other programs make of this, daresay Crafty et al. will have it all
>worked out and resolved in about 5 seconds flat ;-(
>
>P.S it finally managed ply 13 as I was typing this up
>
>13 102 327723 2072998497 b5b4 a3b4 a5b4 f6f2 b4b3 c2b1 f8d7 e1d2 a7a1 h5h6
>g7g6 h4f3 a8a7
>
>54 minutes to decide white is a pawn up after avoiding the sac.
>
> Regards Geoff
crafty only says b4 as taking the rook fails low at 3 plies...
2 0.00 -- 1. ... gxf6
2 0.00 -0.09 1. ... gxf6 2. gxf6+ Kh8 3. fxe7 Qxe7
2 0.00 -1.29 1. ... Bxf6 2. gxf6
2-> 0.00 -1.29 1. ... Bxf6 2. gxf6
3 0.00 -- 1. ... Bxf6
3 0.00 0.23 1. ... Bxf6 2. gxf6 g6 3. hxg6 hxg6
3 0.00 -0.58 1. ... Bc6 2. Rf4 Rd8
3 0.00 -1.12 1. ... b4 2. Rf4 bxa3
3-> 0.00 -1.12 1. ... b4 2. Rf4 bxa3
4 0.02 -1.41 1. ... b4 2. g6 Bxf6 3. gxh7+ Nxh7
4. exf6
4-> 0.02 -1.41 1. ... b4 2. g6 Bxf6 3. gxh7+ Nxh7
4. exf6
5 0.03 -- 1. ... b4
5 0.06 -0.87 1. ... b4 2. g6 hxg6 3. hxg6 Bxf6 4.
gxf7+ Qxf7 5. exf6 Qxf6 6. cxb4
5-> 0.07 -0.87 1. ... b4 2. g6 hxg6 3. hxg6 Bxf6 4.
gxf7+ Qxf7 5. exf6 Qxf6 6. cxb4
6 0.09 -- 1. ... b4
6 0.15 -0.34 1. ... b4 2. g6 hxg6 3. hxg6 Bxf6 4.
exf6 gxf6 5. gxf7+ Kxf7 6. cxb4
6-> 0.20 -0.34 1. ... b4 2. g6 hxg6 3. hxg6 Bxf6 4.
exf6 gxf6 5. gxf7+ Kxf7 6. cxb4
7 0.58 -0.58 1. ... b4 2. Rgf1 bxa3 3. bxa3 Bxf6
4. gxf6 g6 5. hxg6 hxg6
7-> 0.63 -0.58 1. ... b4 2. Rgf1 bxa3 3. bxa3 Bxf6
4. gxf6 g6 5. hxg6 hxg6
8 1.06 -0.47 1. ... b4 2. Rgf1 b3 3. Bd1 Bxf6 4.
gxf6 g6 5. hxg6 hxg6
8-> 1.18 -0.47 1. ... b4 2. Rgf1 b3 3. Bd1 Bxf6 4.
gxf6 g6 5. hxg6 hxg6
9 2.01 -0.28 1. ... b4 2. Rgf1 bxa3 3. bxa3 Bxf6
4. gxf6 g6 5. hxg6 hxg6 6. Rg1 Bc6
9-> 2.43 -0.28 1. ... b4 2. Rgf1 bxa3 3. bxa3 Bxf6
4. gxf6 g6 5. hxg6 hxg6 6. Rg1 Bc6
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