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Subject: Re: start your engines ...

Author: Jonathan Kreuzer

Date: 19:37:10 03/09/04

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on an AMD 1.8ghz, time until mate in 9 is declared:

Ruffian 1.01:     5.0 seconds
Slow Chess 2.89b: 7.4 seconds
Crafty :          ??? seconds (let it run for 2 minutes)

I've noticed that Crafty quite often has trouble declaring mate, and I've
wondered why (it doesn't hurt playing strength since Crafty is good at finding
the best move quickly.)

One guess is that Crafty gets bad best moves in the hash (ie. moves that lead to
non-mating 'fail-highs' when there's a mate in 1 or 2 present, so instead of
quickly discarding the entire line by searching the mating move first, it has to
search one or a bunch of other moves very deeply before it finds the mating
move.) Even using Internal Iterative Deepening, if you use IID with a small
window, put the fail-high move in the hash, then in no situations use IID again,
when the window is widened to be mate finding, your hash move is probably now a
bad best move.

Note: I don't know what Crafty actually does. Also mate finding speed depends on
lots of factors, but the one mentioned above can sometimes be a big one.



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