SNAFU

I have hit a bump in the road, metaphorically speaking. A really big bump, such that even though my car might have lost a wheel, I am hoping it will still drive me to the thesis defense. So it is simple. The blue and the red curve should be the same. As much as you might squint, look at the graph askew or jump up and down, there is no way those two curves are going to match. The red curve is the simulation and the blue curve is physics. It becomes a moment of concern when your simulations do not obey the laws of physics. Consequently, the many, many hours I have spent baby-sitting computers have been for nothing, nada, zilch. That's right, worthless.

I am not a happy camper. Luckily, I am not the person who wrote the simulation code, which shall remain nameless - so thankfully, the self-loathing has been kept to a minimum. I have alerted them to the problem and I am told "code development" is now in progress (read: in 6 months we might have an answer). I am just bummed that I didn't find the mistake earlier, ideally before I started writing my thesis. My advisor gave me a pep talk: "We are in the business of experiment, not simulation. The data is good, regardless. That and it's sunny outside." So I am feeling a little better, a little less panicky, but still bummed, totally bummed.

Misery loves company ... even if it is a cartoon character. Since it doesn't look like I am graduating anytime soon: an excellent time sink - www.phdcomics.com

Comments

[Dave Bacon]

> It becomes a moment of concern when your simulations do not
> obey the laws of physics.

Any chance it's new physics?

As a theorist I get to be dillusional all the time thinking that I've discovered something new. Usually lasts about a day until I think about the details real hard and then "whoops, I was wrong!" So maybe you can just be dillusional for a while, believing that the simulation is working correctly, but that there is some new physics here?

[Aaron]

Maybe you should just restrict your thesis to the domain 3 < x < 4. ;)

Seriously, I can't imagine how horrible this must feel. :'( May your luck turn around soon!!!

p.s. If Dave is right, send us plenty of pictures from Stockholm. ^_^

p.p.s. PhD?! I guess it *is* a small world after all! Yes, it's frightening how easy Cecilia is to relate to...

[xoxo]

"Maybe you should just restrict your thesis to the domain 3 < x < 4."

Ah, yes...a mathematician no less! Make your own physics. That was very funny. Thank you.

So is your SNAFU because the simulation software isn't accurate with regard to the laws of physics or is it because of some conceptual mistake or bad assumptions that you made in your theory?

Good luck. :)

[Caolionn]

Yeah, I immediately assumed I did something wrong. I had three people check the blue curve and they all agreed with me. Leaves the simulation as the only recipient for blame. I'm trying to now find some other code which actually obeys the laws of physics (the well-known established laws, as opposed to the potentially "new" version).

[Stephan Mertin]

Never believe an experiment until it's been confirmed by theory.

[Caolionn]

Stephan -

I can only believe a theorist would be believe such things or, at least, I hope only a theorist would say that out loud.

[Sparks]

If it makes you feel any better, it doesn't feel as bad as sitting in a conference room a few years into the PhD, watching someone else present your thesis as a complete piece of work because you were both working on the same topic and they beat you to it...

[Paul O'Connor]

"As much as you might squint, look at the graph askew or jump up and down"

Hmmmmm..... no jumping up and down required.If you tilt the graph on the Z-axis just so, a head-down view shows both lines (no longer icky non conforming 'curves')sitting happily atop one another.

Voila !

I expect a credit.

[Caolionn]

Sparks: You totally win. And I am a bad person for saying it, but it does kinda make me feel a little better. Thanks.

Paul: I wonder if MATLAB is willing to tilt a 2D graph in 3D space ... hmmm.

[Sparks]

"Sparks: You totally win."

Huzzah!
:-)

And if it eases the "oh, *bugger*!" sensation, excellent. Besides, the moral of my particular story was that the PhD topic I moved onto afterwards was one I actually felt to be "better" in that it was more to do with the basic mathematical theory and less to do with implementation as many robotics PhDs tend to be. So it's a combination of "This too, shall pass" and "These things always work out for the best". Cheesy or what? :-)

[mark jamison]

Hi All:

You are wasting your time trying to break down matter into the smallest elements, even at the quantum level you will see everything is working in pairs to give form, and eventually leads to emptiness. You will see that matter and energy are always combining together with other elements to give form. The reason physics is completely wrong, nowadays is because the underlying philosophy is based on seeing the world as objective particles.Both Einstein and the Buddha, especially Nagarjuna have elaborated that sense based reality-experience is totally unreliable. You cannot seperate your mind from matter. Mind really is energy-awareness and beyond that I don't know what it is. That's the great thing about the mystery of the Universe you will never find the god-particle because it's an illusion. God is really having a good laugh.

[panos]

really sorry about your sim...But a great comic strip!

[arvind]

Sorry to hear about the simulations.

Been there, done that. Not an expert by any means of simulations, but it took a while for me to realize that I can generate anything from simulations. I remember 3 years ago when I started my grad studies and simulated something using a commercial tool. I showed results to my boss (realizing very little that result was totally unphysical). He laughed and said if your simulations are correct, I suggest you quit your PhD and start a company, you will be a billionaire for sure. Needless to say I was new in the game of simulations and believed that the code somehow magically dumps the truth on the screen.

A year later I was working with some complicated code which had more rigorous physics and convergence methods. I adored the people who wrote the code (one of the best in their field) yet it didn't take me long to get strange results. There is only so much truth to the binary digits in the code.

Cheer up ... :) things could be worse.
-a