Halt rules in draughts

[M Winther]

In International Draughts, three Kings against one King is seldom a win,
which tends to make the game drawish in grandmaster practice. Diverse
halt rules have been proposed as a remedy.

C. Freeling's killer rule is defined thus: "when a King occurs as final
capture, the captor must halt behind the enemy piece". This means that
*two* Kings will win against a lone King. Arguably, it means an overly
radical departure from the standard rules. After all, one should be able
to play confidently for a draw with one Man less. To fight for a draw
belongs to the game. So the ideal is perhaps that *three* Kings against
one King is a win. This is accomplished with the following halt rules.

A.K.W. Damme's sequential halt rule: "at the final capture of a series,
the captor must halt behind the enemy piece". It could be argued that
this reduces the power of the King too much during the middlegame.

J. Anikejev sequential halt rule ("killer light"): "When a King occurs
as the final capture of a series, the captor must halt behind the enemy
piece". This works fine. But it is possible to reduce the effects on
middlegame King maneuvers even further, with the following proposal.

M. Winther's sequential halt rule: When *two* Kings occur as the final
captures of a series, the captor must halt behind the enemy piece. Also
here, three Kings will win against a lone King. To capture two Kings in
the last two jumps is a rare occurrence, so the draughts player will
hardly experience this King as essentially different than the normal.

I have implemented all these halt rules as variants in my program
"Draughts with Deferred Backwards Capture":

http://mlwi.magix.net/bg/draughtsdeferred.htm
(http://www.two-paths.com/bg/draughtsdeferred.htm)

Mats Winther