Author: Robert Hyatt
Date: 10:24:38 04/22/02
Go up one level in this thread
On April 21, 2002 at 19:29:39, Will Singleton wrote:
>All,
>
>[D]5nk1/2R3p1/r4p2/4P3/p2R2N1/7P/1r4P1/7K b - - 0 42
>
>The question is, my prog wants to play a3, and doesn't see the forced repetition
>until ply 9. I've just thrown away my old buggy rep code, and replaced it with
>a dedicated hash table. The new stuff seems to be debugged and working (maybe),
>but there must be a trick to getting this position earlier. An extension,
>perhaps?
>
>Will
First, if I play a3, Crafty sees the perpetual at depth=4:
4 0.03 -1.53 2. Rd6 Rxd6 3. exd6 a2 4. Rc1 Nd7
4 0.04 ++ 2. Nxf6+!!
4 0.04 0.00 2. Nxf6+ gxf6 3. Rg4+ Kh8 4. Rh4+ Kg8
5. Rg4+
4-> 0.04 0.00 2. Nxf6+ gxf6 3. Rg4+ Kh8 4. Rh4+ Kg8
5. Rg4+
5 0.05 0.00 2. Nxf6+ gxf6 3. Rg4+ Kh8 4. Rh4+ Kg8
5. Rg4+
(3) 5-> 0.07 0.00 2. Nxf6+ gxf6 3. Rg4+ Kh8 4. Rh4+ Kg8
5. Rg4+
(2) 6 0.09 0.00 2. Nxf6+ gxf6 3. Rg4+ Kh8 4. Rh4+ Kg8
5. Rg4+
(2) 6-> 0.15 0.00 2. Nxf6+ gxf6 3. Rg4+ Kh8 4. Rh4+ Kg8
5. Rg4+
Second, Crafty doesn't like a3, period, but I assume that it would see this
at depth=5 and switch away from it, if it did like it at shallow depths.
2-> 0.00 -1.31 1. ... Ne6 2. Rc8+ Kf7
3 0.01 -0.99 1. ... Ne6 2. Rc8+ Kh7 3. Rd7
3-> 0.01 -0.99 1. ... Ne6 2. Rc8+ Kh7 3. Rd7
4 0.02 -0.72 1. ... Ne6 2. Rc8+ Kh7 3. Rd7 f5
4 0.05 -1.09 1. ... fxe5 2. Nxe5 a3 3. Rg4 Ne6
4-> 0.06 -1.09 1. ... fxe5 2. Nxe5 a3 3. Rg4 Ne6
5 0.09 -0.87 1. ... fxe5 2. Nxe5 a3 3. Rg4 Ne6 4.
Re7
5-> 0.13 -0.87 1. ... fxe5 2. Nxe5 a3 3. Rg4 Ne6 4.
Re7
6 0.21 ++ 1. ... fxe5!!
(2) 6-> 0.37 -1.26 1. ... fxe5 2. Nxe5 a3 3. Rg4 Ne6 4.
Re7
7 0.62 -1.16 1. ... fxe5 2. Rd8 e4 3. Kh2 Ra5 4.
Re7 a3 5. Rxe4
7-> 0.79 -1.16 1. ... fxe5 2. Rd8 e4 3. Kh2 Ra5 4.
Re7 a3 5. Rxe4
8 1.27 ++ 1. ... fxe5!!
8 1.93 -1.60 1. ... fxe5 2. Nxe5 a3 3. Rg4 g6 4.
Rc6 Rxc6 5. Nxc6 a2 6. Ra4
8-> 2.16 -1.60 1. ... fxe5 2. Nxe5 a3 3. Rg4 g6 4.
Rc6 Rxc6 5. Nxc6 a2 6. Ra4
Which means that (a) your extensions might not be working correctly, or
(b) your repetition detection is not working correctly... If you are
using the hash signature, perhaps that has a flaw, such as incorrectly
including castling or enpassant status after it should be removed or
something similar...
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