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Subject: Re: Draw by 2nd repetition?

Author: Bruce Moreland

Date: 10:06:17 03/31/99

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On March 31, 1999 at 12:46:42, Jeremiah Penery wrote:

>On March 31, 1999 at 12:08:49, James Robertson wrote:
>
>>I have noticed from a post below that some people consider the position a draw
>>if it has repeated twice in the search. What are the advantages and
>>disadvantages of this? I am currently waiting until 3rd repetition; is this
>>worse?
>>
>>Thanks,
>>James
>
>From what I've seen, it's good to wait until the 3rd repetition.  Very often,
>I've seen times when Crafty (which scores a draw at 2nd repetition) finds that
>it can force the position to repeat (for the second time) and so scores it as a
>draw, even when the opponent has any number of winning moves it can play before
>the third repetition.  It often plays inferior moves thinking it can draw by
>repetition.
>I'm not sure where it could be better to detect draws after the second
>repetition - it seems it'd be just as easy, and more reliable, to detect them
>only at the third rep.

My program was playing a game against Greg Kennedy a long time ago, and the
following situation occurred.

The program was down two pawns and was completely lost.  But Kennedy made a
mistake, and my program made a move that won a pawn.  At this point the best
move from Kennedy's point of view was to undo the move he'd just done.  My
program's move forced him off of something he was defending, and he had to go
back to where he was, and now the program could simply take a pawn that was
sitting there for free, vastly improve its chances for a draw.

But that's not what it did.  The move it made to win the pawn was also
retractable, so it chose to repeat the position, and scored this as 0.00.

Of course, rather than repeating his mistake, Kennedy chose a better move and my
program was down two pawns again.

bruce



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