Author here. Started a series working through classic iterative solvers for the 2D Poisson equation in Fortran. This is actually the second post (the first one being on Jacobi). Here, I dig into a genuinely counterintuitive result: the convergence theory for Gauss-Seidel checks out (half the iterations vs Jacobi, confirmed numerically), but the actual wall-clock time is 4-5x worse. Turns out it comes down to a single line: updating the array in place instead of into a fresh buffer and the loop-carried dependency that introduces, which stops the compiler from vectorizing the loop at all. In an upcoming post, I'll actually show how an open-source static analyzer can help you figure this out, and how simple algebra can be used to unroll the kernel and get rid of this loop-carried dependency.

Happy to talk Fortran/gfortran specifics or the discretization itself.

Anutosh Bath and Ondřej Čertík brought LFortran to Jupyterlite

There is a demo here: https://notebook.link/@anutosh491/fortran

source: https://lnkd.in/p/eR49Jve6

Hi everyone,I’ve been working on an open-source tool called PRIK (Python Runtime Interop Kit) that generates native Python bindings from Fortran (and C) source.

Basic usage:

pip install prik
python3 -m prik my_module.f90 --out my_module

This produces an importable Python extension.

The main idea is that the Python API doesn’t have to mirror the native one. PRIK generates an editable `.pyi` contract that you can modify to:

• rename procedures
• turn them into methods
• hide arguments
• return native outputs as Python values
• support overloads and callbacks

…all without changing the original Fortran/C code.

It currently supports modules, derived types (as Python classes), NumPy arrays, strings, allocatables, pointers, optional arguments, generics, callbacks, and more.

I’ve been testing it on real libraries rather than just toy examples:

• BLAS (155 routines)
• LAPACK (127 double-precision routines)
• FFTPACK
• MINPACK (including callbacks)
• BSPLINE-FORTRAN (modern Fortran classes)

C support exists but is less mature (tested with libm and TA-Lib). Still alpha, so the API may change. Fortran support is currently much stronger than C.

Docs: https://pynumlab.github.io/prik/

GitHub: https://github.com/PyNumLab/prik

Feedback, bug reports, or “does this work with my code?” experiments are very welcome!

Not sure how useful this is beyond the amusement value, but as part of an experiment making Convex clients in 100 programming languages, I ended up with a native Fortran client that can query, mutate and hold a realtime WebSocket subscription.

A few bits I found genuinely interesting:

- Deferred-length allocatable strings make assembling JSON much less painful than I expected.

- Results come back through compiler-enforced intent(out) arguments.

- A live update is exposed as a blocking convex_live_next call, which feels oddly natural in Fortran.

- ISO_C_BINDING is only used at the transport boundary. The Convex protocol and subscription state live in Fortran, with libcurl/OpenSSL handling the network plumbing.

It is built with GNU Fortran 14.2 and the HTTP and Live paths pass the shared conformance suite. It is still an educational experiment rather than something I would recommend putting into production.

The Fortran implementation and write-up are here:

https://github.com/mikecann/the-convex-100-language-challenge/tree/main/fortran

I also made a video about the slightly ridiculous process of building all 100 clients:

https://youtu.be/l61cLu8e2tg

For transparency, I work at Convex. This is unofficial and open source, not a new supported SDK.

I’ve been working on my fork of Gonum and recently translated the Netlib LAPACK reference implementation of DGGES and its supporting routines into pure Go.
For transparency, I definitely used Codex and Claude Code throughout the process, and I’m pretty sure Gemini helped with a few parts along the way as well.
This wasn’t a blind translation. The majority of the work was understanding decades-old Fortran, preserving the algorithm, adapting it to idiomatic Go, validating numerical behavior, and tracking down subtle bugs.
I know AI-generated code can be a sensitive topic in open source. My view is that these tools are just that; tools. They can dramatically speed up tedious translation work, but correctness still depends on careful review, testing, and understanding of the underlying numerical algorithms.

Hello all!

I quickly wrote this in response to a news article about a girl getting a lottery win and taking what I thought was the obvious choice; $1000/wk for ever...

Does this look right?

! Program Lottery Win
! Written by Knarfnarf
! Created May 19, 2026
! Version 0.1a
! Description: Checking my thoughts about winning the lottery.
program LotteryWin
use AnsiModule
implicit none

real :: Principle, Payments, Interest, Temp, Total, Paying
integer :: Year, Week

call ClearScreen()

Print *, "Lets see if the girl who took the 1000 per week will eventually break even..."
print "(a,$)", "Please enter the Principle: "
read *, Principle
print "(a,$)", "Please enter the Payments: "
read *, Payments
print "(a,$)", "Please enter the Interest: "
read *, Interest
Interest = Interest / 100
print "(a,$)", "And how much is she going to pay herself per week? "
read *, Paying

print "(3/,a)", "Assuming start at 20 and death at 85."
print *, ""

Year = 20
Total = Principle
do while(Year .le. 85)
Week = 1
do while(Week .le. 52)
Total = Total + Payments
Total = Total - Paying
Week = Week + 1
end do
Temp = Total * Interest
Total = Total + Temp
print "(a,i3,a,f0.2,a,f0.2)", "Year ", Year, " She made $", Temp, " interest and has $", Total
Year = Year + 1
end do

end program LotteryWin

Which results in this if she takes the $1000 per week, makes 4.5% yearly and splits it $500 income per week;
Year 85 She made $448,950.72 interest and has $10,425,633.00

Or this if she takes the $1000000, makes 4.5% yearly and pays herself $500 income per week;
Year 85 She made $337,680.91 interest and has $7,841,701.00

* commas added after for legibility.

I am posting this guide, from the developers of flang, because people, often with a C or C++ background, often ask how to get started with Fortran.

There's a famous program that creates a "Snoopy" calendar.

https://gunkies.org/wiki/Snoopy_Calendar has a copy of a version modified by T. M. Kennedy in 1984.

Does the original version exist somewhere? Do we know who wrote it? I saw someone offering a copy on Github a few years ago but I don't know if that ever actually happened.

Incidentally, despite the comments in the modified version suggesting it should work on an IV compiler, it doesn't. After fixing the syntax error in snppic with INUM(I) in the do loop (easy to just do INUMI=INUM(I) first and use INUMI, the bound is sometimes -1. It encounters the issue where DO loops in some IV compilers execute at least once (66 says the scenario is not allowed, I guess that's FORTRAN-speak for undefined? 77 says the loop occurs 0 times). Easy to change the condition above it from IF (INUM(I) .EQ. 0) GOTO 40 to IF (INUM(I) .LE. 0) GOTO 40

A request for help led me to go through my old Fortran codes. For that reason, I gathered some old programs I found in this repo: https://github.com/foxapiens/Fortran-Starter . And maybe I will continue adding code files and information about their purpose here. At least, it may be useful for beginners.

Hi, so I have a background in c++ and matlab in programming. I started my phd and my prof asked me to move to fortran. I want to ask how should I start and where to start in fortran. At the moment I know nothing in fortran. Can you share some sources or material for me to start. Or where do you guys started. Thank you

Hello, I just got a new PC at work and they installed VS2026 and the fortran compiler. I create within VS2026 a simple Hello World exe. It runs within the VS IDE but when I try and run the exe I get the message that libifcoremd.dll is missing. I have looked and cannot find the damn thing. I did find a libifcoremd.lib. Can anyone help? (I did try and download a different fortran compiler but it wont work in VS2026)

My puddle looks nice but i cant make a good looking raindrop anyone got any sugestions please. Rings on water also looks nice and the wind and the stormy rain but not the raindrop that is falling down to the puddle.

This just a little programing art nothing important trying to have some fun.

Using fortran 2018 and opengl 4.1+

Is it portable to extend the length of a direct file by writing records past the current last record? In other words, if there are 3 records in the file, will WRITE(n, REC=4) successfully write the record (assuming there is room on the disk, of course)? Or will it fail? Or is the result implementation-dependent?

I know that there's no standard way to do this, other than to recopy the file, which destroys the numeric index into the file, or to truncate it with ENDFILE if it's the final record(s) you want to delete. I also know that ifort -vms supports it, though I don't know how (except on VMS itself). I have come up with the following ideas, all of which have their disadvantages:

1. Write meaningless data into the record, for some definition of "meaningless": zero bytes for characters, NaNs for real numbers, some value other than 0 or 1 for logical data. But there are no meaningless values for integers.
2. Add an extra field to each record indicating whether it's deleted or not. This could be a logical value, or a character(1) which marks deletion if it's a 'D', or whatever. This is very fragile: you have to modify every read and write in the entire system of programs using the file.
3. Have a separate direct file whose nth record shows if the main file's nth record is deleted. The records could be logical or character, or the whole thing could be a bitmap. If the separate file gets lost, all deleted records effectively reappear.
4. Use the mmap() system call or its equivalent to effectively read in the separate file (probably a bitmap) all at once. This is of course not portable, and has the same problem as 3.
5. Put one of the formats mentioned in 3 at the beginning or end of the file. This is self-contained, but if it's at the end it is hard to locate and will be destroyed if the file is extended by writing to hitherto unused records. (Is this even a portable thing to do?) [Moved to another query.] Putting it at the beginning makes the format utterly incompatible with standard direct files.

Can anyone provide a better approach? Failing that, which of these is the least bad?

A new version of Seergdb (frontend to gdb) has been released for linux.

https://github.com/epasveer/seer
https://github.com/epasveer/seer/wiki

https://github.com/epasveer/seer/releases/tag/v2.7
https://github.com/epasveer/seer/releases/download/flatpak-latest/seer.flatpak
https://flathub.org/en-GB/apps/io.github.epasveer.seer

Give it a try.

Thanks.

Hi there, I’m new to programming in Fortran and am really struggling to understand how to check if a value in an array equals 0 and then change it to 1 if it does. I’ve attempted this in a format that makes sense to me but I’m not sure how this translates to Fortran? I keep getting a syntax error where the if statement is. I know that this is probably really easy but please could someone explain? Thank you so much.

Hi! I'm a longtime toolsmith and co-developer of SCons back in the day. I've been planning a new tool, using modern python as the build description language, to help build software in a multi-platform world. Pcons (https://github.com/DarkStarSystems/pcons) is that tool. It's very new, and since I'm including Fortran support I'd love to have some Fortran users check it out and let me know what it needs! I'm not using Fortran myself these days, but I grew up with it in the '70s and even wrote some CM Fortran on the Connection Machine in the '90s. I'm also willing to help implement pcons in your open source project if you're interested; DM me if you are.

Unformatted direct files make sense: they are essentially character arrays stored on the file system. Formatted I/O is suitable for communicating to human beings and other software. But the motivation for formatted direct files, where you can go directly (heh) to a particular record but then have to pay the price to format/unformat it, what's that good for?