RE: Heisenberg and measurement intrusion....
- From: "Ted Coyle" <oracle-l@xxxxxxxxxxxx>
- To: <Mark.Bobak@xxxxxxxxxxxxxxx>, <niall.litchfield@xxxxxxxxx>
- Date: Wed, 1 Aug 2007 12:12:37 -0400
Mark, Niall et al., thanks for the great replies.
I think my response to the respondent is in line with the group.
My response was this simply this:
"I think you meant the ?Observer Effect?, not Heisenberg which deals with
observed precision." http://en.wikipedia.org/wiki/Observer_effect
Respondent: "Nope I meant what I meant look at the O?l formula. Slightly
different but really both apply"
So I did, and as seen here
http://en.wikipedia.org/wiki/Uncertainty_principle,
I fail to see how the formula makes the respondent's statement regarding
measurement elimination any clearer, particularly regarding Planck's
constant. I'm not a physicist or mathematician, so translating the formula
to something that equates to "don't intrude on your baseline with pesky
measurements" would require more effort that I'm willing to expend, but I do
have fondness for physics, know how to read, and can use web browsers, so I
did some research.
Here are two definitions, one from the link above and one from the American
Institute of Physics attributed to Heisenberg himself. Neither mandates
anything regarding measurement elimination, base-lines without measurement,
or anything of the sort.
A) "Heisenberg uncertainty principle gives a lower bound on the product of
the standard deviations of position and momentum for a system, implying that
it is impossible to have a particle that has an arbitrarily well-defined
position and momentum simultaneously"
B) The more precisely the position is determined, the less precisely the
momentum is known in this instant, and vice versa.
--Heisenberg, uncertainty paper, 1927
http://www.aip.org/history/heisenberg/p08.htm
Here's a third that appears closest to the respondents original intent.
C) "The very process of measuring one quantity alters a complimentary
property." http://spiff.rit.edu/classes/phys314/lectures/heis/heis.html
This does not state that we turn off measurements. In fact, reading the
entire post, it appears that without measurement, there can be no
uncertainty.
"If one wants to be clear about what is meant by "position of an object,"
for example of an electron..., then one has to specify definite experiments
by which the "position of an electron" can be measured; otherwise this term
has no meaning at all.
--Heisenberg, in uncertainty paper, 1927
Further exploration:
http://en.wikipedia.org/wiki/Heisenberg%27s_microscope
This link appears to validate my assertion that Heisenberg's uncertainty is
about precision and not the "observer effect" or measurement intrusion.
Here's a good paper:
http://www.cs.uoregon.edu/research/paracomp/papers/tpds92/tpds92.pdf
It mentions Heisenberg's Uncertainty by saying it defined the bounds of
measurement certainty. It then defines instrumentation uncertainty
principle as: "Simply put, performance instrumentation manifests an
Instrumentation Uncertainty Principle". It doesn't say that Heisenberg
mandates an unmeasured base line first.
I have most of the well known Oracle and quite a few other well respected
performance texts and I don't think I've seen any of them mention Heisenberg
in relation to not measuring. Cary Millsap and Jeff Holt's Optimizing
Oracle Performance (2003) does have a special boxed section devoted to
Heisenberg on p157 under the sub-heading "Measurement Resolution". In fact,
on p150, "measurement intrusion effect" is attributed to the tpds92.pdf
paper included above. But the Heisenberg references refer to precision
limits not intrusion.
I agree in base lining without, or with as little measurement intrusion as
possible, but I believe Heisenberg's Uncertainty is a derivation of the
measurement, not its abstinence. I've always thought it describes an
inversely proportional relationship by stating that the more I can know of
one element; the less I can know of another, or rather, observation level
affects knowledge.
If you've gotten this far, my point is, do not guess, do not make stuff up,
and do not say something is when it is not. More importantly, be precise in
reference, gracious in acceptance, and understand that we can't know
everything.
If I'm wrong, I'm wrong. Maybe my precision is off.
Again thanks for the replies.
Ted
Some more links:
http://van.physics.uiuc.edu/qa/listing.php?id=1228
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Bobak, Mark
Sent: Tuesday, July 31, 2007 4:54 PM
To: oracle-l@xxxxxxxxxxxx; oracle-l
Subject: RE: Heisenberg and measurement intrusion....
Hi Ted,
I see what the person is saying. Yes, there is a measurable effect on
performance, due to instrumentation. (This is really due to observer
effect, not the Uncertainty Principle.)
However, without instrumentation, you don't really have a system that can be
tuned or optimized. You NEED that data to understand the system and its
performance profile. Without it, you have no idea which way to turn when
performance becomes an issue. Therefore, system instrumentation is an
integral part of the system. It's not optional. So regardless of whether
measurement intrusion costs you 1% or 10% or whatever, in overall
performance, it's a necessary cost.
To borrow a thought from Tom Kyte: Overhead is something you can do
without. Instrumentation is NOT something you can do without. Therefore,
there is no overhead cost to instrumentation. It's not an overhead, it's a
requirement.
Finally, I'd say to the person making the objection: "Ok, what if we
eliminate all instrumentation from the system, and discover that the system
performs (for example) 10% better. So what? Are we going to remove all
instrumentation, in order to save that 10%? Of course not, we NEED
instrumentation so that we know what to do when something goes wrong! And,
if there is no circumstance where the instrumentation can be removed, then
why do we need a baseline without it? What will that accomplish, other than
demonstrating the performance improvement of a system configuration that
will never see the light of day?"
Just my two bits.....
-Mark
--
Mark J. Bobak
Senior Database Administrator, System & Product Technologies
ProQuest
789 E. Eisenhower, Parkway, P.O. Box 1346
Ann Arbor MI 48106-1346
+1.734.997.4059 or +1.800.521.0600 x 4059
mark.bobak@xxxxxxxxxxxxxxx
www.proquest.com
www.csa.com
ProQuest...Start here.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Ted Coyle
Sent: Tuesday, July 31, 2007 3:40 PM
To: 'oracle-l'
Subject: Heisenberg and measurement intrusion....
I'm on an Oracle performance project and a project participant made a
statement regarding measurement intrusion.
Is the statement below accurate?
"So the Heisenberg uncertainty principle mandates we run without monitoring
as a baseline."
I responded with a wikipedia link which I'll send later, but I'd like to get
opinions first. :)
Regards,
Ted
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