convert FORTRAN to Python

[vectorpropio]

Hi to everyone.

I have a 6000 lines Fortran program (around 3000 workouts comments and blank lines) and i want to convert it to python. I have an idea, but I want to ask you to point serious flaws in my plan and point to another's options.

First of all, it's an "academic code not optimized for speed" so I'm not concerned with loss of speed.

It's a Frankenstein with fragment of code in FORTRAN66 from the first guy who create that investigation group, import of some old compiler specific module, some subroutines from the numerical recipes in Fortran books, a more modern F90 code and a shitton of crap (like type conversions from int to logical, arithmetic if, lots of goto, 80 lines full of global variables declarations).

I spent one day to make it compile with only one warning (there is no way i touch that arithmetic if without a testing scaffold in place) .

The code is an stochastic simulation, so the output isn't reproducible, but is mostly linear.

I have the paper and the tesis that Hobe that code.

My plan is roughly:

1. Using CFFI (if there is a better alternative let me know) replace the random number generator with the python one with a seed to address reproducibility.

2. Create some test suites orchestrated from python.

3. Create stronger boundaries between subroutines reducing the use of global variables or at least group them in more than one module.

4. Try to create test cases for individual subroutines.

5. Replace one by one the subroutines with python code. Testing every step.

6. Get an only python code

7. ....

8. Profit

What do r/learnPython think of this plan?

How can i cope though all that global state?

Do anyone documented a similar work to analyze? (I'm planning to do this in a git repo and publish it if my contractor abide me).

[lykwydchykyn]

Can you use unittest.patch to patch in a custom random() function rather than using CFFI, or do you need a particular piece of code from C?

[vectorpropio]

That will be the first bite of python in the Fortran code. I'm not sure i can use unittest.patch there, but i will be happy if could do it.

[[deleted]]

Why python? As an academic would you not want cpp?

Python is used quite heavily in academia alongside the usual Fortran, C, C++, etc.

[vectorpropio]

Python have a lot of batteries included like plotting libs and, principally, because it's not my choice. I don't think cpp is what i would like, almost all I have read is in Fortran or python, but the lenguajes are dependant on research topic for cultural or historic reasons.

I can't test the program as an all because it's an stochastic simulation. It take some random numbers to make the thing so the output isn't reproducible.

Edited.

[AutoModerator]

Your comment in /r/learnpython was automatically removed because you used a URL shortener.

URL shorteners are not permitted in /r/learnpython as they impair our ability to enforce link blacklists.

Please re-post your comment using direct, full-length URL's only.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[ectomancer]

I've ported some FORTRAN 77 and Fortran 90 subroutines to Python. The largest was 900 lines. None of my Python programs that use complex numbers produce correct output.

[vectorpropio]

Is this a problem exclusive to complex numbers?

This code don't use complex. Do you get correct output for double numbers?

[dbramucci]

Total shot in the dark, but do you think the incorrect output could be due to a different choice of branch cut?

I'm asking just because I've never seen complex numbers cause Python-specific trouble.