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Subject: Re: GM Says he wouldn't know that someone was using a computer

Author: Robert Hyatt

Date: 06:41:27 09/16/98

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On September 16, 1998 at 08:29:30, Jouni Uski wrote:

>On September 16, 1998 at 00:49:49, blass uri wrote:
>
>>You can see that the opponent thinks about obvious moves.
>>
>>Uri
>
>Rebel is very clever in this respect: it moves faster if moves are obvious.
>I am not sure if any other program behaves this way.
>
>Jouni


Almost all do that I know of.  For different reasons.  Later versions of
Cray Blitz counted the nodes searched for each root move, and if one move
really dominated the total node count, we considered that move "easy" and
played it after using much less than the normal amount of time.  We used
other ideas to implement this in earlier versions, such as when the move is a
recapture and it was the only way to recapture a piece at the root.  We replaced
this in the late 80's with the node count trick and found that we could
generally pick even non-capturing moves that were obvious, very quickly, such
as when you attack the queen and it only has one safe square to move to.  All
other moves produce ugly scores, with quick cutoffs.

We did find that the above is dangerous, because in one ACM game we played a
move saying that it was an "obvious" move when it was not.  It was just
hellishly complicated with checks, so that it took 10X the nodes of all the
other moves together.  Which made it look like an obvious move, when it wasn't.

But most programs do notice that obvious recaptures can be played quicker than
normal, and all that I know of move instantly if there is only one legal move
to make (such as when checked).

But this is not the best way to catch someone using a computer.  And the GM
discussed at the start of this thread is not answering the right question.  In
a tournament, it would be most unlikely to see someone cheat like this.  But
should he play on a chess server, I'd bet he would be able to pick out a
computer cheater quite quickly.  All the GM's I personally know on ICC have
no problems doing so...



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