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Subject: Re: a question about evaluation of positions when the king is in check

Author: Colin Frayn

Date: 13:26:37 04/26/00

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>>Some programs can have main line ends with a mate without understanding that it
>>is a mate(I saw that it happened to Crafty and Junior).
>>
>>I think that knowing if the position is checkmate or not checkmate is an
>>important knowledge.

I agree.  My program checks every move it generates to see if it gives
checkmate, but it does this in a highly optimised way so that it is as fast as
possible.  The time expenditure is extremely small.

In some (rare) positions my program searches considerably faster than, say,
Crafty because of this.  It just seemed to be like an obvious thing to do at the
time, and seeing as the slowdown was negligible I implemented it.

>>How much time does a chess program need to find if a position is checkmate or
>>not checkmate?
>
>Not a lot of time.  But the problem is that a big number (number of leaf
>positions) times a small number (time to do the checkmate test) turns into a
>big number

Depends on how small the small number is :)  The total time spent in my program
doing _all_ checkmate tests adds up to less than 2% of the total running time on
average problems, occasionally much less and rarely more.

Cheers,
Col



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