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Subject: Re: Wrong Colored Bishop Endings

Author: Howard Exner

Date: 03:47:18 11/23/97

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On November 22, 1997 at 08:31:35, Chris Whittington wrote:


>I don't accept the 'solutions' for #5, here's why:

>This series of test positions is not about being clever and then
>'solving' each position. Its purpose is to demonstrate the issue of bad
>bishop and rook file pawns together with some difficult special case
>issues - against the idea of just searching the position out into the
>disatance.

>I posit that #5 is semi-unsolvable without some very special case code
>that is (a) very difficult to code,

Just a wild thought here. If after Na5 and b6xa4

8/8/p7/P2b2K1/8/P3k3/8/8 w

if black cannot
safely capture on a5 then on a3 in "X" number of plys then call it a
draw.
Obviously to win black must remove the pawns.

Rebel 8 sees that the capture sequence is futile and makes king and
bishop moves to keep the white king from approaching. Could these moves
be pruned out in this special "Wrong colored bishop" ending since
there is no tempo gains here for black?

Take the above epd and move all the pieces up one rank. Your program
and most others would munch the pawns and win.



 >and (b) very unlikely to have been
>coded.

I posted this one for that reason to see if someone coded this or if
a deep search would eliminate the other choices.
>
>I posit that the 'solutions' to #5 are simply the result of choosing the
>'right' move as the least bad loss; and that this is a matter of luck
>for the solvers.

Is this a form of chess knowledge (ie: making your opponent find the
longest win). Lasker's tenacious defense comes to mind where he pulled
out draws and wins in poorer positions.

> Ernst has already said that Dark Thought scores #5 as
>-3.5 or something.

Through the deep search DarkThought found that Na1(only other reasonable
choice) was futile.
>
>To be listing results like the table above strikes me as crass
>materialism, or quantity over quality

Recall that I posted these and asked for submissions as to how programs
play them out. You and others responded with posts so the table is
just a summary of those submissions.

 I like such tables because I'm
most interested in examining the positions that show wide
variance among solution times.

>- since a solution (in this test,
>given the nature of this test) that is created for the wrong reason, is
>no solution at all.

The "nature of the test" for me was to see if programs would play the
right
move. I do agree with you that it is unlikely that a program contains
code for #5 but I don't want to underestimate you or other programmers.
Never know?

>
>Chris Whittington



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