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Subject: Node counting confusion.

Author: Don Dailey

Date: 13:43:39 01/17/98


In a message from Ed Schroder we run across this statement:

> It depends of course how you count NPS.
> I remember yours is different then mine.


I have long suspected the  lack of a "standard" way  of doing this.  I
think most of us  use a similar method but  it's not so clear.  I have
always used the method of  counting strictly legal moves and requiring
that they be  fully executed by the program  but  I can think  of good
arguments for counting in other ways.

For example, most good programs  will evaluate a position that  hasn't
occured yet to save a significant amount of  time.  An example of this
is in quies where you know in advance a  capture move will be punished
brutally.   I do  not   count count these  as  nodes  but it  could be
strongly argued that I should.

I believe some programs count "moves generated."  This is not an issue
if  you   are using a   purely incremental  move generation  but would
inflate (or deflate  depending on your point  of view) the node counts
since most of these moves get cut off before they are even considered.

Another method  is to count end  nodes  only, which will  deflate your
node counts    over  my method  but   probably  not  by large  amounts
(depending on a lot of factors like the shape of the tree.)

Some programs generate and "make" illegal moves as part of the testing
for legality.  I view this as inefficient but leads to the question of
whether these should be counted as nodes.   When I do check testing to
determine if  a move is  legal should I count this  as a node since in
some sense I'm definitely evaluating it?  I don't, but maybe I should?
This adds a significant number of nodes to the nodes/second count.

I am always  reluctant to attach  any significance  to big  (or small)
node count claims.  Until you can actually compare apples to apples it
can be quite misleading.  Also this is  certainly not the true measure
of  a   chess program but   nevertheless  it's  an  interesting topic.
Certain programs claim such high node counts that it's  hard for me to
believe they are counting  nodes the same way  that some others  might
be.

What is known about the various programs and how they  count nodes?  I
am quite interested in this since  it can give  some insights into how
each program works.


P.S.

Please  forgive me if this discussion  has already made the rounds but
I've never heard any of it myself.


- Don




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