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Subject: Re: what is a lazy eval function?

Author: Daniel Clausen

Date: 01:03:56 10/23/03

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On October 22, 2003 at 19:47:34, macaroni wrote:

>is it an evaluation function where positional stuff is only calculated if you
>arn't just getting killed (or killing). So if you dropped a rook, there isn't
>much point checking position stuff, so just return -5 and save the time.

It's not really a separate eval function but more a test in the middle of eval
to return early.

If the score after the simple-to-calculate eval-terms is less than the current
alpha and there's no chance that all the hard-to-calculate eval-terms can bring
the score to at least alpha, there's no point in calculating them, since the
move will be rejected anyway. That's a lazy eval for this position.

If you just have a very simple evaluation (like material and PSQ), you can get
high percentage of lazy evals because the max. positional score is not high
anyway. The more sophisticated your evaluation, the less lazy evals you get.

I don't know how much speed reduction modern chess engines get from lazy eval,
but I fear it's not that much. (it's a lot in my simple engine though :)

Sargon



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