Author: Richard A. Fowell (fowell@netcom.com)
Date: 23:27:21 09/09/99
Go up one level in this thread
As Dan points out later, this is "White being crushed" and the EPD is:
8/p7/P5p1/7p/7P/4kpK1/8/8 w - -
(I put the "with EPD" in the hopes to save folks the trouble Dan and I
went through).
Anyway, I tried this on a few programs.
===============
MacChess
===============
MacChess 5.01, given White, takes 8 ply and 3 seconds to conclude mate 6:
02/01|00:00:00| 27| -293| Kh3 f2 Kg2
03/01|00:00:00| 169| -295| Kh3 Kf4 Kh2 f2
03/01|00:00:00| 379| -290| Kh2 Ke2 Kg3 f2
04/01|00:00:00| 1200|-1060| Kh2 Ke2 Kg3 f2 Kg2 f1=Q+ Kg3
05/01|00:00:00| 4545|-1069| Kh2 Ke2 Kg3 f2 Kf4 f1=Q+ Kg5 Qf5+ Kh6 Kd3
06/01|00:00:00| 60485|-1209| Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 Qf3 Kg1
Qg3+ Kh1 Qxh4+ Kg2
07/01|00:00:01| 255518|-1217| Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 Ke3 Kg3 Qf2+
Kh3 Qf3+ Kh2 Kd4 Kg1 Qg3+ Kh1 Qxh4+
08/01|00:00:03| 702572|-M6 | Kh2 f2 Kg2 Ke2 Kg3 f1=Q Kh2 g5 hxg5
Kf3 g6 Qg2+
=================
Sigma Chess
=================
Sigma Chess 4.01 Lite takes 10 ply (1 second, 57601 nodes)
to see it's demise, coming up with the same line Bob gives:
Kh3 f2
Kg2 Ke2
Kg3 f1Q
Kh2 g5
hg Kf3
g6 Qg2#
=================
HIARCS 7.0
=================
HIARCS 7.0 sees the mate at 9 ply, and is happy:
09 1.Kh2 f2 Mat-8
In analysis mode, it does better, seeing the mate in 6 at 9 ply.
Richard A. Fowell (fowell@netcom.com)
On September 10, 1999 at 00:19:37, Robert Hyatt wrote:
>Here is an interesting position given to me by Steffen Jakob:
>
> /p/P5p/7p/7P/4kpK/// w
>
> +---+---+---+---+---+---+---+---+
> 8 | | | | | | | | |
> +---+---+---+---+---+---+---+---+
> 7 | *P| | | | | | | |
> +---+---+---+---+---+---+---+---+
> 6 | P | | | | | | *P| |
> +---+---+---+---+---+---+---+---+
> 5 | | | | | | | | *P|
> +---+---+---+---+---+---+---+---+
> 4 | | | | | | | | P |
> +---+---+---+---+---+---+---+---+
> 3 | | | | | *K| *P| K | |
> +---+---+---+---+---+---+---+---+
> 2 | | | | | | | | |
> +---+---+---+---+---+---+---+---+
> 1 | | | | | | | | |
> +---+---+---+---+---+---+---+---+
> a b c d e f g h
>
>
>Obviously black is getting crushed. He has one move, Kh3, which leads to a
>mate in 6. Steffen asked me to try this and Crafty found a mate in 4, which
>doesn't exist. I spent the entire day debugging this thing and here is what
>I found:
>
>If you recall the discussion here a couple of weeks ago, I reported that I store
>absolute mate scores (EXACT scores) in the hash table, and that I adjust them
>so that they are always stored as "mate in N from the current position". This
>has always worked flawlessly for me, and still does.
>
>For bounds, I once tried adjusting the bounds as well, but found quirks, and
>left them alone. Wrong answer. To fix this mate in 4 problem, I decided to
>adjust the bounds as well, but I now set any bound value that is larger than
>MATE-300, by reducing it to exactly MATE-300, but still using the "LOWER"
>flag to say that this is the lowest value this position could have. For bound
>values < -MATE+300, I set them to exactly -MATE+300 and leave the flag as is.
>
>This position is cute. Because not only is it a mate in 6, but there are
>transpositions that lead to mate in 7, mate in 8, and there are shorter (but
>non-forced) mates in 4 and 5. And there are stalemates, and positions with
>1 legal move, and so forth.
>
>You ought to find the following variation as one mate in 6:
>
>Kh3, f2, Kg2, Ke2, Kg3, f1=Q, Kh2, g5, hg, Kf3, g6, Qg2#
>
>If you find a shorter mate, it is wrong. If you find a longer mate, you
>are probably just extending like mad on checks (crafty finds a mate in 8 at
>shallow depths (9 plies, 2 secs on my PII/300 notebook), and doesn't find the
>mate in 6 until depth 10, 3 seconds.
>
>It is a good test as the transpositions are real cute with white's king caught
>in a tiny box, but with several different moves that triangulate and transpose
>into other variations...
>
>If you get it right, you have either handled the bounds right, or else you are
>very lucky. IE Crafty 16.17 gets this dead right. But if I disable the eval,
>it goes bananas, yet the eval is not important when mate is possible.
>
>Have fun...
>
>I did... :)
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