Computer Chess Club Archives




Subject: Re: Using too-shallow mate scores from the hash table

Author: David Eppstein

Date: 11:11:03 07/06/98

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On July 05, 1998 at 14:14:36, Ernst A. Heinz wrote:
>>No, not stupid at all -- just obvious and straightforward. I have used it
>>with good success in "DarkThought" for a long time. :-)

Straightforward, I agree.  Obvious?  It took me a year to notice, maybe I am
slow, but how many other similar little tricks does everyone have to rediscover
for himself (or worse not rediscover)?

I think we really need a good text that will cover all these details.
Bob was talking about doing something like that a while ago; what happened?

On July 06, 1998 at 13:04:17, Robert Hyatt wrote:
>In Cray Blitz (and in crafty, unless I have broken it) I store mates with a
>"draft" of infinity, because a mate is independent of any draft, and is >*always* correct.

You might find a mate in fewer moves if you searched longer; there's no
game-theoretic value to doing so (assuming your time management code isn't
stupid) but there is a certain aesthetic value.

As I said, I looked at crafty and didn't see it, which was what led me to think
someone other than myself might not already know about it.  StoreBest() and its
relatives certainly detect whether a score is mate, but only use that to modify
word1; the draft lives in word2 and doesn't seem to be conditional on whether
the score is mate. LookUp also has some mate-score-conditional code, but only
after it's discarded too-shallow positions.  So if it isn't in these two places,
where are you hiding this piece of code?

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