Computer Chess Club Archives




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

Author: Robert Hyatt

Date: 10:58:52 01/26/00

Go up one level in this thread

On January 26, 2000 at 12:58:07, Ed Schröder wrote:

>On January 26, 2000 at 10:03:47, Robert Hyatt wrote:
>>On January 26, 2000 at 03:07:42, Ed Schröder wrote:
>>>On January 25, 2000 at 23:57:33, Ernst A. Heinz wrote:
>>>>> In a one by one setting it does not matter at all.
>>>>Still not convinced: a quiescence node that produces a direct
>>>>"stand pat" cutoff obviously generates less work than one
>>>>which fails to do so -- even in hardware!  *** QED ***
>>>>Or am I missing something?
>>>Something else... I always wondered about this free 4-ply evaluation. I
>>>can understand that evaluation for the current position done in hardware
>>>is possible in a few cycles. I can't understand this also to be true for
>>>4 plies as it should involve: search, hash table, q-search etc. In other
>>>words a complete chess program.
>>They didn't do this as you describe.  The chess processor did a traditional
>>alpha/beta search to a depth of 4 (this was user-settable, but going deeper
>>in the hardware meant going shallower in software) followed by a traditional
>>quiescence search and _then_ the hardware evaluation.
>>This means that the 4 ply search is _not_ done in 10 clocks... only the
>>evaluation.  The 4 ply search takes a variable amount of time depending on
>>the position.
>So there is no free 4 ply evaluation at all. Makes sense. Must have
>misunderstood in the past.

Right.. the evaluation is "free" because it is so fast.  But the 4 ply search
runs just like any other 4 ply search, except it is far faster than any single
cpu today can run it (remember, 2 to 2.4M nodes per second search speed on a
single chip).  So the chess chip ends up looking like a "little computer" that
can do 4 ply searches, + extensions, + a q-search, + a complex eval, and it does
all of that at roughly 10 cycles per node, where a chess program typically takes
4000 cycles and up per node...  But the chip is very much like a 'mini chess
program complete with everything.'  They didn't do hashing, but they had a
hash interface built into them, but according to Hsu he didn't have time to
build a 16-way ported shared memory for the 16 processors on a single SP cpu.

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