Fortran was a requirement for my undergrad. There are often times thousands of lines of legacy Fortran in national laboratories.
Why physicists still use Fortran (2015)
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Re: Why physicists still use Fortran (2015)
#72Earlier quoted context omitted.
Pretty much just size! There was about 20,000 lines of it, it's legacy code that has been gradually added to since the 1980s, so it would have taken a while to rewrite all the parts to work with each other. Perhaps some day though.
What's the code do? [physics grad level description would be fine] It must surely be generic equipment management, you're not running experiments in physics that are > 30 years old, surely?
Started in the 80s doesn't mean the code is 30 years old, as they keep adding to it and modifying it in Fortran. Plus most of the analysis part is probably just math routines that don't need modification ever after.
Re: Why physicists still use Fortran (2015)
#73Earlier quoted context omitted.
Pretty much just size! There was about 20,000 lines of it, it's legacy code that has been gradually added to since the 1980s, so it would have taken a while to rewrite all the parts to work with each other. Perhaps some day though.
20,000 lines of code really doesn't seem like that much. I probably output that much in about 2-3 months of biomedical research so there has to be more to it than that.
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...
Re: Why physicists still use Fortran (2015)
#74"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…
Yep. Most of my programming classes were either in pascal or c when I was in undergrad, but in my physics courses, all the way through my graduate education, I used FORTRAN. It's because physics doesn't change that much over the years, FORTRAN code that is time-tested and that works exists and there's no need to re-invent the wheel in another language when more interesting and important problems exist to solve.
David Baker's Rosetta code, which made him a pile of money, is IMO a spectacular example of craptastic C++ written by people who really didn't understand C++ but didn't let that deter them from using every single feature of the language, badly. Some years back we tried to port it to CUDA but there were so many levels of indirection, dereferencing, and virtual functions that it was nearly impossible to make any progress.
In contrast, porting the 30+ year old molecular Dynamics package AMBER to CUDA took about 3 months and probably established me as a CUDA expert. In my opinion its well-maintained Fortran 90 code was far easier to understand and refactor.
While my primary languages today are C++ and CUDA, there is something clean about Fortran when it comes to understanding underlying algorithms. I have a similar opinion about well written C code.
Re: Why physicists still use Fortran (2015)
#75A lot of the arguments in this post can simply be rebutted with basic abstractions. Things like "Dynamically allocating and deallocating ... 2D array" is easy in C++. You could easily have someone define a MathArray class and turn this messy fortran code: real, dimension(:,:), allocatable :: name_of_array allocate(name_of_array(xdim, ydim)) Into something that looks like auto *my_matrix = new MathArray (); The code t…
MPI is availabe for C too. It even had C++ bindings but there were deprecated since not even boost used them.
Re: Why physicists still use Fortran (2015)
#76"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…
His response was "You could do that and it would probably be enough to earn your PhD, since it'll take you at least three years. But I suspect you'll want to work on something else during that time". as someone who had contact with that codebase, do you have any insights as to why that is? Was it the sheer size of the thing? Was it some nuance that Fortran had as an advantage over other languages? was the math just d…
I'm taking (educated) guess, because people involved estimating rewrite where all physicists and not developers. And certainly not developers with 5+ years of experience. Which is minimum I'd trust with archtechting major rewrite.
Re: Why physicists still use Fortran (2015)
#77Earlier quoted context omitted.
Sounds like your IT department botched the wrapper. Wouldn't a more successful candidate likely just have used an abstraction layer between the .net conventions you were expecting and whatever the native code was doing?
Nope, the library itself is sold that way. See the documentation: https://www.nag.co.uk/numeric/DT/nagdotnet_dtw02/html/conten...
Ah I see, makes more sense. It would be a massive undertaking to abstract that API into something else.
Re: Why physicists still use Fortran (2015)
#78"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.
Note that the SPICE Toolkit[1] is still written in Fortran today, translated to C using f2c, and the C version used as the base for other language support. The Fortran part is unlikely to ever go away, since support for processing past missions is crucially important and all that processing code was written in Fortran. Also, talk about your stable, backward compatible APIs...
Re: Why physicists still use Fortran (2015)
#79Earlier quoted context omitted.
Some of the Numpy code is coming from 1970s: it uses BLAS that originates from 1979. https://en.wikipedia.org/wiki/Basic_Linear_Algebra_Subprogra... Immense amount of effort was put in performance, correctness, feature set, and numerical stability of such widely used libraries. Replacing the without a very good reason is hardly feasible.
I needed a .net math library. My IT department insisted on my trying a wrapper around a Fortran library (I believe purely because they had a license already). All the classes and variables names are short hexadecimals strings. None of the interface is idiomatic to .net (the library only has void returning methods which pass error codes as byref arguments instead of using exceptions, requesting a parameter for the len…
Your .NET wrapper doesn't need to expose the same name or calling convention. That's why you use a wrapper: to abstract away distasteful non-idiomatic decisions in the wrapped API.
Re: Why physicists still use Fortran (2015)
#80Earlier quoted context omitted.
Potentially your "rival groups" will have a long term advantage now though. This might be bad for the graduate students that did the work, but could be good for the professor and group over the next decade. Graduate students need to think in terms of 4-6 years while forward looking professors might want to think in terms of 5-15 years.
That was without a doubt pretty bad for those grad students' careers. That kind of work shouldn't have been done by anyone without tenure.
I don't know. Having "rewrote X kloc of scientific Fortran to modern idiomatic C++" on your CV should get you to the head of the line in many places when looking for a job.