Author: Robert Hyatt
Date: 19:57:56 10/19/00
Go up one level in this thread
On October 19, 2000 at 22:07:42, Michael Neish wrote:
>
>Hi,
>
>I wonder whether anyone might be able to explain why my program cannot see the
>solution to BT2630 #3 below
>
>[D]5r1k/p1q2pp1/1pb4p/n3R1NQ/7P/3B1P2/2P3P1/7K w - -
>
>The solution is 1. Re6, leading to the following tactics:
>
>1. Re6 Kg8
>2. Rxh6 gxh6
>3. Qxh6 f5
>4. Qxf8+ Kxf8
>5. Ne6+ forking King and Queen and gaining material.
>
>My program does not see this if it searches 8-ply deep, even though it is doing
>check extensions, and should therefore see it (I think) because there are two
>checks in the sequence.
>
>If I make it do a 9-ply search it does find the right move (but well over the
>time limit), and funnily enough, the PV that it gives (the correct one) extends
>to eleven ply (because of the two checks).
>
>So we're going from not seeing far enough at 8-ply, even though it should, to
>seeing further than you need to at 9-ply.
>
>The only strong program I have got, HIARCS 7.0, finds the move at 4-ply. Some
>heavy-duty extensions at work here I think ...
>
>Thanks for any feedback.
>
>Mike.
I find this at 8 plies with crafty, although not the winning score. At depth=8,
score goes from -1.13 for f4, to +.45 for Re6. At depth=10 it goes to +7.
Here is the output (off of a slow notebook). The 8ply, 9ply and 10 ply
PVs might show why this takes more depth than you would expect:
8 9.22 -1.13 1. f4 Qb7 2. Re2 Bd5 3. Bf5 Qc7 4.
Be4 Bxe4 5. Rxe4
8 13.50 ++ 1. Re6!!
8 15.69 0.45 1. Re6 Kg8 2. Rxh6 gxh6 3. Qxh6 f5
4. Qxf8+ Kxf8 5. Ne6+ Ke7 6. Nxc7 f4
8-> 15.72 0.45 1. Re6 Kg8 2. Rxh6 gxh6 3. Qxh6 f5
4. Qxf8+ Kxf8 5. Ne6+ Ke7 6. Nxc7 f4
9 17.76 0.65 1. Re6 Kg8 2. Rxh6 gxh6 3. Qxh6 f5
4. Qxf8+ Kxf8 5. Ne6+ Ke7 6. Nxc7 f4
7. Kh2
9-> 18.38 0.65 1. Re6 Kg8 2. Rxh6 gxh6 3. Qxh6 f5
4. Qxf8+ Kxf8 5. Ne6+ Ke7 6. Nxc7 f4
7. Kh2
10 27.93 ++ 1. Re6!!
10 48.26 7.20 1. Re6 Kg8 2. Bh7+ Kh8 3. Rxh6 Re8
4. Nxf7+ Qxf7 5. Qxf7 gxh6 6. Bg6 Re1+
7. Kh2 Rh1+ 8. Kxh1 Bb7
10-> 48.88 7.20 1. Re6 Kg8 2. Bh7+ Kh8 3. Rxh6 Re8
4. Nxf7+ Qxf7 5. Qxf7 gxh6 6. Bg6 Re1+
7. Kh2 Rh1+ 8. Kxh1 Bb7
11 59.76 ++ 1. Re6!!
11 1:44 10.24 1. Re6 Kg8 2. Bh7+ Kh8 3. Rxh6 g6 4.
Bxg6+ Kg7 5. Ne6+ Kf6 6. Be4+ Ke7 7.
Nxc7 Bxe4 8. Qe5+ Kd7 9. fxe4
11-> 1:46 10.24 1. Re6 Kg8 2. Bh7+ Kh8 3. Rxh6 g6 4.
Bxg6+ Kg7 5. Ne6+ Kf6 6. Be4+ Ke7 7.
Nxc7 Bxe4 8. Qe5+ Kd7 9. fxe4
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