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Comment: Re:Q: Why Are Scientists Still Using FORTRAN in 20 (Score 5, Insightful) 634

by poodlediagram (#46964951) Attached to: Why Scientists Are Still Using FORTRAN in 2014
My previous supervisor decided to fork our Fortran code for performing quantum mechanical calculations. We'd worked on it for more than half a decade and it was world-class.

He handed it over to a computer science graduate (i.e. a non-physicist) who really liked all the modern trends in CS. Now, five years later:

1. the tarball is an order of magnitude larger
2. the input files are now all impenetrable .xml
3. the code requires access to the outside (not possible on many superclusters)
4. he re-indented everything for no apparent reason
5. the variable names were changed, made into combined types and are much longer
6. as a result, the code is basically unreadable and nearly impossible to compare to the original formulae
7. code is duplicated all over the place
8. it now depends on unnecessary libraries (like the ones required to parse .xml), and it only compiles after a lot of work
9. it's about four times slower and crashes randomly
10. it generates wrong results in basic cases

To quote Linus Torvalds: "I've come to the conclusion that any programmer that would prefer the project to be in C++ over C is likely a programmer that I really *would* prefer to piss off, so that he doesn't come and screw up any project I'm involved with." ... and I feel the same way about CS graduates and Fortran. They have no idea about the physics or maths involved (which is the difficult part), so the do the only thing they know which is to 'modernize' everything, making it into an incomprehensible, ungodly mess.

Fortran, apart from being a brilliant language for numerical math, has the added benefit of keeping CS graduates at bay. I'd rather have a physicist who can't program, than a CS type who can.

(Apologies to any mathematically competent computer scientists out there)

Comment: Re:Wrong interpretation of energy (Score 5, Informative) 135

by poodlediagram (#46912037) Attached to: Is There a Limit To a Laser's Energy?
Exactly.

This is the usual muddle up between energy and intensity.

There is no apparent upper limit to the energy of a photon. The galaxy Markarian 501 emits photons in the teraelectronvolt (TeV) range.

The question here is about intensity. The relativistic energy-moment dispersion, E^2=(mc^2)^2+(pc)^2, which applies to all on-shell particles, has a gap when m>0. This gap, which is about 1 MeV for electrons and positrons, can be overcome when the electric field (generated by a sufficient number of photons, irrespective of their energy) approaches the Schwinger limit of about 1.3 x 10^18 V/m. At this point, virtual electron-positron pairs can be created in abundance because the mass gap has been overcome, and electromagnetism then becomes non-linear. Pumping in more photons after this simply creates more virtual e-p pairs.

Hope that helps.

(IAAP working on this topic).

Comment: Re:And what good would that have done? (Score 5, Insightful) 504

by poodlediagram (#45323793) Attached to: Feinstein and Rogers: No Clemency For Snowden

Quite agree.

Given that James Clapper was perfectly willing to lie to Congress, what would the NSA administration have done to a 29 year old system administrator, had he aired his views to them? He would have been sidelined, fired or arrested, that's what. And we would be none the wiser.

It is amusing that politicians will express the need for public discussion about NSA surveillance and then condemn Snowden in the next sentence. You can't have one without the other.

In my opinion, he is the definitive whistle-blower. He had only one way to reveal the NSA/GCHQ excesses and revealed them in the right way. Further, he gained nothing personally from all this: no money and he seems to dislike the attention. And spending a month in a Russian airport can't be much fun.

He has my gratitude and admiration, and I wish him well.

Comment: Fortran works fine with MPI (Score 5, Informative) 157

by poodlediagram (#44912825) Attached to: A C++ Library That Brings Legacy Fortran Codes To Supercomputers

...and has done for years.

We write a scientific code for solving quantum mechanics for solids and use both OpenMP and MPI in hybrid. Typically we run it on a few hundred processors across a cluster. A colleague extended our code to run on 260 000 cores sustaining 1.2 petaflops and won a supercomputer prize for this. All in Fortran -- and this is not unusual.

Fortran gets a lot of bad press, but when you have a set of highly complex equations that you have to codify, it's a good friend. The main reason is that (when well written) it's very easy to read. It also has lot's of libraries, it's damn fast, the numerics are great and the parallelism is all worked out. The bad press is largely due to the earlier versions of Fortran (66 and 77), which were limited and clunky.

In short, the MPI parallelism in Fortran90 is mature and used extensively for scientific codes.

Comment: 1988 Toyota Olympic Ideas winner (Score 5, Informative) 104

by poodlediagram (#36703002) Attached to: Novel Drive Wheel System Based On Spinning Sphere

This has already been turned into a personal vehicle some years ago. It won the 1988 Toyota Olympic Ideas competition and ran on perpetually spinning Chinese woks. The best link I can find is

http://books.google.com/books?id=1M3e82yGmZMC&pg=PA27&lpg=PA27#v=onepage&q&f=false

Perhaps someone can find a better picture or video.

Comment: Duplicitous encryption scheme (Score 1) 484

by poodlediagram (#34290200) Attached to: Whitehat Hacker Moxie Marlinspike's Laptop, Cellphones Seized

I had an idea for a duplicitous encryption scheme. Not sure if it's already been done.

It's very simple: you can use one of two keys A and B. If you use key A, then you get the plain-text you wish to keep private. If key B is used, then you get some diversionary data (something innocuous, but for which encryption is plausible). The encrypted files would be larger, but the scheme could be made so that you would never know if there are two sets of data or only one.

Thus if you encounter nosey border guards, you type in key B and show them your soft-core pron collection ("I didn't want the wife to see it, Officer...")

fortune: not found

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