The new features of Fortran 2018 [pdf] | Hacker News Reader

The new features of Fortran 2018 [pdf]

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Modern FORTRAN looks more like Matlab than FORTRAN 77. The syntax has been completely overhauled since at least ‘95.

For a while I was translating my Matlab codes to FORTRAN; it was surprisingly easy. But I was being too naive with array resizings in Matlab and most of the speed gain (which was like 2-3 orders of magnitude) could be achieved in Matlab itself by preallocating memory.

To this day I have the nervous tick of initializing arrays with zeros even in numpy.

> To this day I have the nervous tick of initializing arrays with zeros even in numpy.

I dunno - I wouldn’t call that a nervous tick. If you know or have a good idea of how much memory you need, then it only seems polite to let the runtime/OS know ahead of time.

I think of it like RSVP’ing to a dinner party. Host is very appreciative when they know how many people they’re serving.

It is a tic — if you plan to fill the array anyway there’s no need to set its values on initialization

No but in dynamic languages just making the array before hand can greatly increase efficiency.

Just a mild FYI: That word is 'tic' without the 'k'. Pronounced the same, but a different word.

>To this day I have the nervous tick of initializing arrays with zeros even in numpy.

The typical way to create arrays in Numpy is with `np.zeros(size)`. What is it that you're doing?

Note there's also `np.empty(size)` if you know you're going to initialize all the values in a later step, in which case it can skip assigning zeros to every element.

Or you can create them as outputs from your computations.

Fortran users of HN - what are the best resources (online / books / ...) to pick up Fortran in 2019? Are there any open source codebases you'd consider as good to read through?

Modern Fortran by Milan Curcic seems to be a pretty good book.

https://www.manning.com/books/modern-fortran

Most other ‘modern fortran’ books assume you have knowledge of older fortran versions.

Thanks! "Publication in Fall 2019 (estimated)" at the moment: "8 of 13 chapters available"

Table of Contents and samples on the author's site:

https://milancurcic.com/book/

Here's author's recent series of articles "Analyzing stock price time series with modern Fortran":

https://milancurcic.com/2018/11/06/analyzing-stock-price-tim...

I have the book Modern Fortran Explained by Metcalf. It does a great job of providing modern examples of traditional code as well as examples of the new features.

I second that. The book by Metcalf is the holy bible of Fortran.

This could help someone get started https://learnxinyminutes.com/docs/fortran95/

Ahhh... FORTRAN -- my first language: CDC 3100, 1965. What magic.

FORTRAN77 on a VAXCluster in 1986.

Still have my copy of "FORTRAN 77 For Engineers and Scientists" just in case.

It was very easy to pick up for someone who had only used AppleII or TRS-80 BASIC.

I used to have Fortran77 notepad for hand writing code — later I would type it in. Always began in the 8th column if I remember right?

Yep -- old-school fixed-format Fortran had one column for the "c"(omment) marker, seven for the statement number (maybe 5 plus spaces on either side?), then 72 for the code before you fell off the end of the punch card.

No, you get all 7 spaces for the statement number; live it up a little!

Don't know if it's still the case, but in FORTRAN IV you don't need spaces between keywords and variable names. So when the compiler sees "FORI=2" it has to look still further ahead to decide if this is a for-loop (FORI=2TO9DO) or an assignment to a variable named FORI. Decidedly not a context-free grammar; you can't even figure out the tokens without the ad-hoc parser getting involved.

No. In fixed format form, statement numbers are columns 1-5. "FORI=2TO9DO" is an unclassifiable statement; try "DOII=...".

You’re right! I was remembering columns 73-80 reserved for “card number”.

Oops, on the obvious typo, too late to edit. Aye, aye.

I'm still using a program and occasionally updating it that's mostly in FORTRAN 77. Originally written in FORTRAN IV. Ah, gotta love the nuclear industry. Good code though.

I borrowed this from someone at work once. I never got a chance to write a Fortran app, but the book wasn't bad.

FORTRAN IV Running on DEC PDP11 (11/40, 11/03 and PDT 150)

WAs told in my first week after a hours quick instruction on our 11/40 - to get the book on Fortran from the company library and learn it.

Cool. The WATFIV (Waterloo FORTRAN IV) was what I used in my first college programming class, on a pair of Amdahl 470 (IBM 370 compatible) mainframes, but as a high school kid I had taught myself BASIC and Pascal on the Apple II. At the time, I felt like FORTRAN was a step back in time, but I have more appreciation for it now.

The most notable thing I spotted is they have deleted the arithmetic IF from the language, which must be one of the more characteristic features of classic FORTRAN.

I agree. The non intuitive reason stated is that there is a standard that specifies a sign for zero, and numeric IF doesn't distinguish between them, and it depends upon labels which are hard to optimize.

Another notable capability is that procedures default to recursive and there is a way to state they are non_recursive.

For non Fortran programmers this is what they looked like.

IF ( N ) 6020, 6030, 6999

Basically GOTO 3 different labels, depending whether if N is -ve 0 or +ve

I have used my first jobs standard for statement labeling - which was fairly common, 6000's for goto's 7000 and 8000 for FORMAT statements

What's the degree of backward compatibility with FORTRAN releases? I imagine most FORTRAN codebases as being huge and old, so it makes me wonder how many can adopt the latest versions.

Each new standard usually removes a very small number of features, but Fortran 2018 is mostly a superset of Fortran 77. Most compilers retain absolute backward compatibility, so they can compile a superset of Fortran 66 to 2018, and often some custom language extensions on top.

Only some of the real ancient pre FORTRAN IV stuff has been removed.

I’ve compiled fortran code from approx 1965. Works the same today. I don’t know of anything that is as compatible as standard Fortran code. That being said, quite a few vendor extensions are floating around, and often old codebases rely on a few of these.

You can start with an awesome-fortran list: https://github.com/rabbiabram/awesome-fortran

In my experience nearly all standard old code will still compile just fine, except code which relied on compiler-specific extensions and directives. Unfortunately, there does tend to be a lot of code out there using these proprietary directives.

Things like metacommands [0] will need to be converted to something standard (or removed) to work with modern compilers.

[0] http://www.ousob.com/ng/fortran/ng4e22.php

This will be of help as well:

https://github.com/CodethinkLabs/fortrantools/blob/master/RE...

Most of the patches are upstreamed, but their gcc repo contains the patched versions on top of the latest gcc releases.

I've been really interested in learning Fortran for a while- I work doing a lot of computational stats/ML and typically my tools are python, R, or Golang. Is there any use-case for Fortran in production settings or should I just accept it would be purely a personal satisfaction project?

IMO if you're working with large, multi-dimensional arrays and seamless parallelization (shared or distributed memory) is a plus, I've yet to see a language or framework do it with less effort. Speaking as a long-time numpy user and fan here. :)

For an example of use in production, my business [0] is built around running ~1M lines of parallel Fortran (public domain code) in the cloud. There are many many other uses but tend to be less visible -- under the hood of other software, banking systems, many DOE and DOD projects etc.

[0] https://cloudrun.co

It's very fast and there is a new Manning book about to come out on Modern Fortran that is all about parallel Fortran.

In addition to being fast, I find it considerably easier to read than C++ as it isn't as low level and doesn't have as much noise (at least the later versions like Fortran 90).

It also makes writing numerical code easy as it was truly built for high performance scientific computing.

A lot of older scientific projects run on Fortran and although I know some projects that were migrated to C++, it wasn't due to any defect from the language besides it not being taught very often in colleges now outside of some astrophysics classes where it was once a mainstay in engineering and science curriculums.

There are several compilers available, but a lot of them are commercial and some are expensive. There are free versions as well of course.

Though the main reason (for a while) that Fortran compilers could produce faster code was that they were allowed to assume that variables (including arguments to your functions) don't alias each other.

See http://beza1e1.tuxen.de/articles/faster_than_C.html

I don't understand the "Though" part of this. The only reason any compiled language may be faster than another is because a compiler knows/assumes more about the code (either through users specification, or restrictions of the language).

Yes. That's the remaining reason when compilers for the languages in question have gotten as good as they can get.

The advantages of the proprietary compilers are quite over-sold. GNU Fortran is pretty good, and distinctly more reliable than some. (I don't have experience of the LLVM-based ones.)

WATFOR anyone? My first programming language in college. Spring 1969. https://dl.acm.org/citation.cfm?id=363059

I used WATFIV in 1982.

Fortran 77 was the language I used in my first job in 92 on DOS and Unix. Can't see the benefits over other languages like C, Go, Python though. Unless you've got some specific high performance floating point ops requirements?

Quite a few scientists and engineers have those requirements. I wouldn't choose it for writing a web server or text processing, but Fortran is actually a pretty nice language for dealing with numbers and arrays. It also has decades' worth of well-tested numerical libraries, which can be very subtle and hard to get right.

Thanks to the magic of computer science, we can package up a lot of those libraries for use with other languages as well.

Sort of, but we haven't figured out how to make language boundaries disappear. For example, row- vs. column-major ordering of arrays is an eternal pain when communicating between C and Fortran.

Numpy, R, Matlab, etc. are good scripting languages for a lot of Fortran, but if you ever need to peek under the hood...

Not in C++, thanks to the power of user defined types.

From:

https://scicomp.stackexchange.com/questions/304/c-vs-fortran...

"Sorry for digging up an old thread but it seems that even in 2015, Fortran is being used a lot.

I just came across this (alternate link) list which basically is a list of 13 codes approved by DOE's OCLF facility to run on the 300-petaFLOPS Summit machine which will be made available to researchers in 2018. I tried to find the main language used for the code (based on a quick google search) and here is what I found:

XGC Fortran

SPECFEM Fortran

ACME Fortran (Bunch of climate codes)

DIRAC Fortran (Mostly)

FLASH Fortran

GTC Fortran

HACC C/C++

LS-DALTON Fortran (some C)

NAMD C/C++

NUCCOR Fortran

NWCHEM Fortran

QMCPACK C++

RAPTOR Fortran"

Note: QMCPACK is written in C++ but depends on LAPACK which is again Fortran.

Another example I've given before is the usage statistics for the UK "tier 1" system: //www.archer.ac.uk/status/codes/. Six of the top ten are Fortran that month (I think -- I'm not positive about NEMO). That's probably vaguely representative of typical general purpose HPC systems.

I just love it that Fortran is #1 on the front page.

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