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Subject: Re: Question for Chess Programmers

Author: Dave Gomboc

Date: 17:14:02 12/22/98

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On December 22, 1998 at 10:39:09, Sylvain Lacombe wrote:

>On December 22, 1998 at 07:14:27, Dezhi Zhao wrote:
>
>>On December 22, 1998 at 01:14:12, Sylvain Lacombe wrote:
>>
>>>
>>>>I agree; there are usually a lot of forced mates in a given position, and the
>>>>first one found is usually NOT the fastest.
>>>>
>>>>James
>>>
>>>Well, if iterative deepening is implemented, it will find the fastest mate. If a
>>>mate his found at deep 4, their his no reason to continue the search cause there
>>>is nothing better than mate. But you need a condition for it to stop.
>>>
>>>The only thing i can think of for not implementing the PV play is the extra code
>>>it takes.
>>>
>>>Sylvain.
>>
>>The things are a little complicated than that , because of extensions
>>and null moves. You may find a mate in 6 at depth = 4. But if you continue
>>the search, you got a mate in 5 at depth = 5.
>>
>>Dezhi Zhao
>
>You bet it's complicated, that's why i like it so much. :)
>
>How deeper the extensions might go? I didn't implement the null move or the
>extensions yet. If a mate is returned from an extension, can you rely on that?
>What you say above, is you get a mate in 6 at depth = 4 and then you get mate by
>the opposite side at depth = 5, right? Does that mean that you can't stop at
>depth = 4. If the search got to stop because of the time, ain't it dangerous to
>have taken a move that the search says mate for the engine and actually it's a
>mate for the opponent? I don't get it!
>
>Sylvain.

Here he meant "You may find a mate in 6 (moves) at depth = 4 (ply).  But if you
continue the search, you got a mate in 5 (moves) at depth = 5 (ply).", where 1
move = 2 ply.  So the mate is still for the same player, it's just that if you
continue to the next ply, there might be a faster mate.

Personally, I don't think it's worthwhile to look for a faster mate.  Terminate
early, make the first move of the mate, and on each subsequent move ensure that
you play a move that checkmates in less moves than the last time.

Dave Gomboc



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