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Subject: Re: Quiescence search - checking & check evasion moves and Hsu

Author: Gian-Carlo Pascutto

Date: 13:38:49 04/10/02

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On April 10, 2002 at 00:27:54, Keith Evans wrote:

>When Hsu designed the move generator for Deep Blue he added extra hardware so
>that he could generate checking (even discovered checks) and check evasion moves
>more quickly than his first move generator could. (Compare the diagrams for the
>square transmitters and receivers in the IEEE micro article to those in his
>thesis and to those describing the Belle generator.) He could have generated
>these moves without the extra hardware and design time by iterating through
>moves and throwing away moves which didn't meet the criteria, but apparently he
>thought that the performance of the move generator was important enough in these
>cases to justify adding the complexity.
>
>What's the general opinion on this? Was this time well spent, or was it a waste
>of time? I searched for information on what programs typically do during qsearch
>and couldn't find much of anything directly related. It seems like he would have
>simulated this before commiting to design, and perhaps discussed it publicly
>with some top programmers.

In the qsearch, being able to generate only capture moves fast is
a nice speed advantage. If you want to do checks/check evasions too,
you'll have to generate these moves somehow. If you have to fall
back to your standard movegen, that'll come with a speed loss, so
it makes sense to try to avoid that.

Since qsearch tends to amount to a large % of the nodes searched,
this sounds like an understandable decision.

Note that there are usually a lot less captures+checks/evasions than
normal moves.

--
GCP



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