Computer Chess Club Archives




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

Author: Ernst A. Heinz

Date: 11:02:02 01/26/00

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On January 26, 2000 at 00:31:06, Peter W. Gillgasch 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 ***
>Which is the same as saying that EVAL is faster than EVAL plus
>some other work.
>>Or am I missing something?
>Yes. A "stand pat" cutoff does not interact with the behaviour
>of the parent with regard to spinning off siblings since it is
>from the view of the parent just a fail low, which is the reason
>why you can safely prune away that move. Maybe you should read
>a book about futility pruning 8^)

Unfortunately, futility pruning is unable to lift *all* possible
"stand pat" cutoffs to the parent nodes.

>If you do not analyze the timing behaviour of both the parent and the
>child you do not analyze the timing behaviour of moves and
>hence you do not even analyze nodes. Your view reduced the
>object of your analysis (a tree) to one node.  From a node no tree
>can be constructed hence nothing can be concluded about a tree search
>or their nodal rate...

I thought we were talking about "nodes per second" here, right?!
Your seem to measure something else, IMO.

The gross percentage of cheap nodes definitely influences the
overall search speed as measured in "nodes per second" -- even in
hardware! This gross percentage certainly varies in different
positions. Thus, the overall search speed as measured in "nodes
per second" ought to vary too unless the speed variance was totally
offset by an according speed variance in other nodes -- which is
highly unlikely and unproven as of yet.

But I happily await your proof while maybe writing some more stuff
about futility pruning. :-)


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