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

Author: Robert Hyatt

Date: 17:48:27 09/09/02

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On September 09, 2002 at 20:01:29, scott farrell wrote:

>On September 09, 2002 at 12:27:53, Robert Hyatt wrote:
>
>>On September 09, 2002 at 11:30:01, scott farrell wrote:
>>
>>>This may seem obvious, but my chompster is only a todler.
>>>
>>>I have tried adding it to the score, like:
>>>INFINITY+12  (for mate in six), this does a few bizare things,
>>>like the first move played shows a score of INFINITY+1, the second move
>>>INFINITY+3 (which is obviously from the hastable), and then INFINITY+5 etc etc.
>>>
>>>Is it posible to read it from the hash table?
>>>
>>>I currently read my PV from the hashtable.
>>>
>>>Thanks
>>>Scott
>>
>>
>>It should always be MATE - ply, where MATE is something like +INFINITY
>>or whatever large number you want, and ply is the ply at which you find you
>>have no legal moves and are in check...  that makes deeper mates look worse
>>than shallow mates to the mating side.
>
>Robert,
>
>thanx for that.
>
>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.
>
>Thanks
>Scott

If you are storing mates in the hash table, you have to "correct" them.  The
normal search scores are mate-in-n-plies from the root.  You have to correct
them to mate-in-n-plies from the current position...




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