Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why physicists still use Fortran (2015)

moreisdifferent.com

Post reply on HN
Print view View original

161–170 of 300 posts

Re: Why physicists still use Fortran (2015)

#161

Post by noobermin »

solidsnack9000 wrote: post #158
noobermin wrote: post #124

Some of the points brought up here are in fact correct, mainly legacy, testing, and awesome compilers tuned for supercomputers. However, a lot of these "why fortran" articles (on both sides) I find are written by people who don't dabble enough on both sides of the fence, and are ignorant of what either side offers. For example, numpy implements a lot of the stuff from fortran the author listed, like broadcasting oper…

> ...not to mention the scipy library that contains leagues of the famous fortran codes... This doesn't actually make Python an alternative to Fortran, though -- what it's saying is that no one writes the performant code in Python.

Indeed! But stuff like parsing input files and plotting are tons easier to code in Python than in Fortran. The point is the performant parts are not in Python, but the parts we don't want the difficult baggage can be written in a much easier and kinder language like Python.

Re: Why physicists still use Fortran (2015)

#162

Post by cknight »

dsacco wrote: post #157
ptero wrote: post #150

Earlier quoted context omitted.

Yes, C++ does not buy you that much. Sure, it is a more modern language, but when used by scientists (not software engineers) the advantages are hardly earth shattering. Much of complexity is hidden (as it should be) into libraries. IMO, Python stands a better chance of breaking the Fortran's lock on physics related computing. Give it a few more years and enough numpy-based libraries might make Python a real competit…

I have to be honest with you, as someone who writes in both C++ and Python, I really do not see Python being more of a candidate than C++ for displacing Fortran. Can you clarify why you think Python might be able to do it? For scientific computation with high performance requirements, Python is not competitive with Fortan or C++. For work that continues to happen in Fortran due to "academic inertia", my impression (a…

I worked as a programmer in a molecular dynamics research group for a while. I was asked to work in Python because it was what the boss was familiar with - so there's some of the same inertia happening again, just with a new(er) language, I guess.

Speed is not a huge issue if you're happy to leave your simulation running overnight anyway, or if you have the option to just throw more and more cores at the problem (or in our case, both). The goal is to get your papers published. Code developing/interpreting/debugging time is generally far more serious an obstacle to that goal than simulation speed. I was the only developer there. Everyone else in the group coded on an almost daily basis, but none of them considered themselves programmers, and very few of them actually learn about good programming practices. They're biophysics researchers.

Having not worked in Python much before I was also pretty pleased to find that, having determined that I needed to use Dijkstra's algorithm for path-finding and then working out the smallest Standard Deviation between certain sets of data points, Python came with libraries to do both of those things off the cuff. It's just so easy, I can see why it has a favoured place in this field.

Re: Why physicists still use Fortran (2015)

#164

Post by LeifCarrotson »

osteele wrote: post #112
thicknavyrain wrote: post #24

"Professors usually have this legacy code on hand (often code they wrote themselves decades ago) and pass this code on to their students. This saves their students time, and also takes uncertainty out of the debugging process." This is so true. I'm a PhD student in physics using Fortran for pretty much that reason. At the start of my PhD, in response to my supervisor telling me I should learn Fortran to modify our cu…

"Within a month of his arrival, Randy solved some trivial computer problems for one of the other grad students. A week later, the chairman of the astronomy department called him over and said, “So, you’re the UNIX guru.” "At the time, Randy was still stupid enough to be flattered by this attention, when he should have recognized them as bone-chilling words. Three years later, he left the Astronomy Department without…

I am unfamiliar with the passage.

But it describes two options:

1. "A staggeringly comprehensive knowledge of UNIX", three years of domain-specific education, and a network of people who trust you to--no, who depend on you to be able to get things done with that knowledge

2. A piece of paper just like everyone else in the department.

And while the former might be more difficult to make use of, I think it could be much more valuable in the long run.

Re: Why physicists still use Fortran (2015)

#165

Post by harigov »

dsacco wrote: post #157
ptero wrote: post #150

Earlier quoted context omitted.

Yes, C++ does not buy you that much. Sure, it is a more modern language, but when used by scientists (not software engineers) the advantages are hardly earth shattering. Much of complexity is hidden (as it should be) into libraries. IMO, Python stands a better chance of breaking the Fortran's lock on physics related computing. Give it a few more years and enough numpy-based libraries might make Python a real competit…

I have to be honest with you, as someone who writes in both C++ and Python, I really do not see Python being more of a candidate than C++ for displacing Fortran. Can you clarify why you think Python might be able to do it? For scientific computation with high performance requirements, Python is not competitive with Fortan or C++. For work that continues to happen in Fortran due to "academic inertia", my impression (a…

Just because python is slow doesn't necessarily mean that every library is also slow. With numpy/scipy, which are written in C with python bindings, scientific computation is pretty fast. Python is fast becoming standard language for data science with so many tools like notebooks that make it extremely easy to do many things. I am not sure how well it compares to Fortran but it is no brainer to use it over C++, especially for research needs.

Re: Why physicists still use Fortran (2015)

#166

Post by aleph_naught »

dwc wrote: post #78
thicknavyrain wrote: post #24

"Professors usually have this legacy code on hand (often code they wrote themselves decades ago) and pass this code on to their students. This saves their students time, and also takes uncertainty out of the debugging process." This is so true. I'm a PhD student in physics using Fortran for pretty much that reason. At the start of my PhD, in response to my supervisor telling me I should learn Fortran to modify our cu…

When I was working for LROC, most of the planetary geologists used IDL (Fortran-ish in many ways) but there was still plenty of actual FORTRAN floating around. Oh, look, in the last couple of years this legend of photometry worked up this new method and here's the associated Fortran code. That kind of thing. I did actually rewrite both IDL and Fortran, but it was always smallish, single-purpose programs or functions.…

Just before I left JPL, the SPICE team had announced a plan for a complete rewrite in C++. The SPICE team is exceptionally small (especially considereing how widely used and impactful the software has been). IIRC since the team’s inception, to the time I left, it has been about 4-5 people. Their primary goal has always been stability and correctness over speed. Recalling a conversation with Boris, they have something like 2.5 million lines of test code. So it would take some time to port over. The codebase is probably the most documented I have ever seen, every mathematical deduction is described in great detail.

That being said, as someone who has integrated CSPICE into several C++ and python projects, the modernization would be a very welcome change. The current arch depends far too much on global state, and none of it is threadsafe.

https://naif.jpl.nasa.gov/naif/Toolkit_evolution_R2

Re: Why physicists still use Fortran (2015)

#167

Post by robotresearcher »

LeifCarrotson wrote: post #164
osteele wrote: post #112

Earlier quoted context omitted.

"Within a month of his arrival, Randy solved some trivial computer problems for one of the other grad students. A week later, the chairman of the astronomy department called him over and said, “So, you’re the UNIX guru.” "At the time, Randy was still stupid enough to be flattered by this attention, when he should have recognized them as bone-chilling words. Three years later, he left the Astronomy Department without…

I am unfamiliar with the passage. But it describes two options: 1. "A staggeringly comprehensive knowledge of UNIX", three years of domain-specific education, and a network of people who trust you to--no, who depend on you to be able to get things done with that knowledge 2. A piece of paper just like everyone else in the department. And while the former might be more difficult to make use of, I think it could be muc…

No, he left without a degree.

Re: Why physicists still use Fortran (2015)

#168

Post by rxhernandez »

cocoablazing wrote: post #118
coldtea wrote: post #73

Earlier quoted context omitted.

20,000 lines of code casually churned out in 2-3 months will be a nightmare to a) understand, b) maintain, much less to rewrite...

It sounds like he’s talking about scripts generated for research, rather than code for components intended to be persistent.

Precisely this.

Re: Why physicists still use Fortran (2015)

#169

Post by ptero »

dsacco wrote: post #157
ptero wrote: post #150

Earlier quoted context omitted.

Yes, C++ does not buy you that much. Sure, it is a more modern language, but when used by scientists (not software engineers) the advantages are hardly earth shattering. Much of complexity is hidden (as it should be) into libraries. IMO, Python stands a better chance of breaking the Fortran's lock on physics related computing. Give it a few more years and enough numpy-based libraries might make Python a real competit…

I have to be honest with you, as someone who writes in both C++ and Python, I really do not see Python being more of a candidate than C++ for displacing Fortran. Can you clarify why you think Python might be able to do it? For scientific computation with high performance requirements, Python is not competitive with Fortan or C++. For work that continues to happen in Fortran due to "academic inertia", my impression (a…

A disclaimer -- I do not work in physics, however a couple of recent physics Ph.D. that I work with expressed similar views.

Speed is not nearly as important now as it was 10-15 years ago. A typical scientist's worstation has 20 CPU cores. If I want to use 100 CPUs for a few days, it is trivial and 1000 is easy to get. Thus the fact that Python is slow(er) does not bother me unless I am setting up something major.

What matters though, is the availability of libraries that let me reliably run my experiments. If there is a bug, it must be in my code, not the library -- a "discovery" caused by a software bug is humiliating. This is where Fortran shines and Python is not quite there yet -- the decades of beating on those libraries made them very well understood and trusted.

Re: Why physicists still use Fortran (2015)

#170

Post by CardenB »

harigov wrote: post #165
dsacco wrote: post #157

Earlier quoted context omitted.

I have to be honest with you, as someone who writes in both C++ and Python, I really do not see Python being more of a candidate than C++ for displacing Fortran. Can you clarify why you think Python might be able to do it? For scientific computation with high performance requirements, Python is not competitive with Fortan or C++. For work that continues to happen in Fortran due to "academic inertia", my impression (a…

Just because python is slow doesn't necessarily mean that every library is also slow. With numpy/scipy, which are written in C with python bindings, scientific computation is pretty fast. Python is fast becoming standard language for data science with so many tools like notebooks that make it extremely easy to do many things. I am not sure how well it compares to Fortran but it is no brainer to use it over C++, espec…

Isn’t numpy written in Fortran?
Post reply on HN