RE: Heisenberg and measurement intrusion....

From: Ted Coyle <oracle-l_at_webthere.com>
Date: Wed, 1 Aug 2007 12:12:37 -0400
Message-ID: <000c01c7d456$c7641750$3921a8c0@medecision.com>

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.

"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"
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_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Bobak, Mark
Sent: Tuesday, July 31, 2007 4:54 PM
To: oracle-l_at_webthere.com; 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

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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_at_il.proquest.com
www.proquest.com
www.csa.com

ProQuest...Start here.

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] 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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http://www.freelists.org/webpage/oracle-l

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http://www.freelists.org/webpage/oracle-l Received on Wed Aug 01 2007 - 11:12:37 CDT