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Subject: Re: Forced moves

Author: blass uri

Date: 03:16:34 07/30/99

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On July 29, 1999 at 23:07:51, Robert Hyatt wrote:

>On July 29, 1999 at 21:47:26, Peter McKenzie wrote:
>
>>On July 29, 1999 at 20:54:08, Bruce Moreland wrote:
>>
>>>
>>>On July 29, 1999 at 18:58:12, Ian Osgood wrote:
>>>
>>>>Do other program authors curtail the search when there is a forced move at the
>>>>root?
>>>>
>>>>How do you detect that a root move may be forced?
>>>>
>>>>Could you compare the values of the best and second-best root moves after a
>>>>search iteration to detect a forced root move?  (Granted, the second-best score
>>>>won't be accurate due to alpha-beta, but I figure that if the difference was
>>>>greater than a queen's value, you could still conclude that the best move was
>>>>forced.)
>>>
>>>The only sure way to do this is if there is only one legal move.
>>
>>Another safe one is if you figure out that all other moves get mated instantly.
>>I don't do that yet in LambChop, but it doesn't sound too hard.
>
>
>How would you discover this?  You get a score for the first move (the one you
>think is obvious) and all the rest fail low and return alpha.

You can get a score for the 2 best moves and not only for the first move.
If you use the 2 options usually only for 1/10000 of your time then in most of
the cases you are 0.01% slower but when the evaluation of the second best move
is mate against yourself you can be faster.

Uri




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