From: Colin Paul Adams COLINA DEMON CO UK>
Date: 3 feb 2000
Subject: CHU: A2 flawed?
Nick has created .caf files (the format for mating problems used by my
program) for all the A problems. I am working through them to check
they are correct.
I did not attempt to "solve" A1 with the computer, as a trial suggests
it will take many days. But I did have a go at A2.
Working through the published solution, and then counting the moves
for the Lion mate, it appeared to be mate in 12, so I set the search
depth to 24, and gave it a try.
To my surprise, after only 37 minutes (I was expecting a few hours),
the computer claims that there is no solution. This is supposed to be
definitive, but it is of course possible that the program may have a
bug (if it fails to generate all possible checks, for instance).
As I am due to release this particular version (2.4) with the mating
problem solving capability on Saturday, I am anxious to see if this
problem is genuinely flawed, or whether it is a bug. Now the computer
only gives the moves for the correct solution, so tracking down why it
thinks there is no solution can be difficult. So I thought I'd see if
I could find a defence myself.
My first thought was that White can try K-6b at move 2. I then came up
with the following line:
1 +DH 2a - 6a
1 S 5b x 6a
2 Ln 6f - 4e
2 K 6c - 6b
3 Ln 4e - 4c
3 K 6b - 7a
4 Ln 4c x 5c (Ln - 5a is much the same)
4 K 7a - 8b
5 Ln 5c x 6a (+DH x 7c must also be considered here, but I think Ph x
7c is a defence)
5 K 8b - 9b
6 Ln 6a x 7b - 7a
6 K 9b - 10b and no mate.
Can people look at this, and see if they can find an improvement for
Black?
Steve, can you have a look at this with Zillions?
--
Colin Paul Adams
Preston Lancashire