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Subject: Re: DB NPS (anyone know the position used)?

Author: Robert Hyatt

Date: 20:53:49 01/26/00

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On January 26, 2000 at 20:03:56, Peter W. Gillgasch wrote:

>
>This is what I think too. Even if they have still significant clock
>cycle difference between "cheap" and "expensive" nodes they can overlap
>the first FIND-AGGRESSOR / FIND-VICTIM operation with the slow eval
>cycle. Anyone cares to post the actual cycle counts given in IEEE micro ?
>
>Anyway, I still believe that the argument regarding the fail low q nodes
>is bogus because it assumes that the rate of fail low q nodes after a 10
>ply full width search plus extensions and a 4 ply hardware search (is this
>a q search only?)

No.  This is a full-width search with extensions, + q-search.  It was
basically the same idea as done in the belle machine, except collapsed to
one chip.



> multiplied with the clock cycle difference between the
>slow and the fast eval can differ so greatly that it is not washed out
>by the overhead move generation and tree traversal cycles which are
>probably in the order of 1,1,2,2,2 = 8 cycles for each "cheap" cutoff.

also remember that this is synchronous logic.  The fast eval can give a quick
exit, but it still takes 10 cycles to exit as I understand it.  As he was very
specific to say 24mhz processors searched 2.4 M nodes per second exactly.  And
his 20mhz procssors searched 2M nodes per second exactly.  That tends to say
that the fast eval/slow eval/other stuff are done in parallel and used as
needed...  It would be harder to design a piece of hardware that had a variable
number of cycles per node without microprogramming the thing...






>
>The whole proposition by Ernst implies implicitly that their on chip
>move ordering is all messed up and their slow eval is painfully slow
>compared with the move generation and tree traversal clock cycles.
>
>I donīt buy that.
>
>-- Peter
>
>>This would change if some of this stuff backs up into the software part of
>>the search, of course...  But we seem to be talking only about the q-search
>>as implemented in hardware, and every node saved is N nanoseconds saved, period.
>
>Bob I really hate it when we share the same opinion 8^)
>
>>(N is roughly 500, exactly 500 for the 20mhz processors, a little less for the
>>24mhz processors).



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