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Subject: Re: how do I determine 'mate in' depth?

Author: Sune Fischer

Date: 04:09:47 09/11/02

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On September 11, 2002 at 06:26:01, Uri Blass wrote:

>On September 11, 2002 at 04:46:56, Sune Fischer wrote:
>
>>On September 11, 2002 at 00:01:16, scott farrell wrote:
>>
>>>On September 10, 2002 at 02:56:01, Sune Fischer wrote:
>>>
>>>>On September 09, 2002 at 20:01:29, scott farrell wrote:
>>>>
>>>>
>>>>>I have tried a variation on that, being :  INFINITY+(100-ply) - so it stays over
>>>>>infinity, so if it finds mate it returns nice a quickly. I guess your way
>>>>>continues to look for a shorter mate.
>>>>>
>>>>>But I still get the same sympton, the first move in the mate sequence returns
>>>>>INFINITY+99 (ie. INFINITY+100-1).
>>>>>
>>>>>I guess is something to do with wierd hashing, or my replacement scheme or
>>>>>something. i hope its not another bug in the hashtable.
>>>>
>>>>You never ever want to go higher than INFINITY, the signs are important here.
>>>>
>>>>Use INFINITY-ply (why add 100?)
>>>>So that INFINITY-1 is mate in 1 ply
>>>>INFINITY-2 mate in 2 plies (1 move) and in general INFINITY-x mate in x plies.
>>>>
>>>>This works well for the a-b algorithm, your opponent will choose the move with
>>>>the highest score as always, so he will pick the move INFINITY-4 rather than
>>>>INFINITY-7, always the shortes way to the mate (you never mate if you take the
>>>>longest (instability)).
>>>
>>>I dont see the big advantage of picking a shorter mate - mate is mate - I win -
>>>thanks for coming - (or more often, oops I lose) - maybe I can loose slower
>>>though.
>>
>>Well, programs are a little different in this respect.
>>If you reverse the scores it will consistently pick the longest way to the mate.
>>That way you are _sure_ never to checkmate.
>
>No
>
>You will finally have no choice because there is not going to be longer mate
>because of the 50 move rule or repetition.
>

I know, but I decided not to bring it up as it would only confuse the issue and
it most likely isn't related to his bug.

-S.



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