CCL: QM codes NOT written in Fortran



Dear Jürgen,

Thank you, I intended to write Python/C but clearly my brain did not communicate that to my fingers! I appreciate you correcting me. Not that you can't write a QM program entirely in Python, but the performance would be too poor to use in any research context.

All the best,

Phil

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Dr Phil Hasnip                  Email: phil.hasnip(_)york.ac.uk
EPSRC RSE Fellow         Web:  www-users.york.ac.uk/~pjh503
Dept of Physics
University of York             Tel:     +44 (0)1904 322225
York YO10 5DD


On Thu, 10 Jun 2021 at 09:47, Jürgen Gräfenstein jurgen.grafenstein#%#chem.gu.se <owner-chemistry(_)ccl.net> wrote:
Dear Phil,

GPAW is actually written in a combination of C (for the hard-core part) and Python (for the high-level layer). You can find more information here:

https://www.sciencedirect.com/science/article/pii/S1877050911000615

Best regards,
Jürgen

_____________________________________
Jürgen Gräfenstein
University of Gothenburg
Dept of Chemistry and Molecular Biology
SE-412 96 Göteborg
Sweden

jurgen.grafenstein(_)chem.gu.se

On 10 Jun 2021, at 04:07, Phil Hasnip phil.hasnip[-]york.ac.uk <owner-chemistry(_)ccl.net> wrote:

Dear Joe,

Yes there are, for example GPAW is written in Python. However, the choice of many QM programs to use Fortran is not simply because they are "old" codes, many newer QM packages have deliberately chosen Fortran over alternatives (e.g. C++). QM simulations are computationally intensive, and Fortran is rather hard to beat performance-wise -- though modern C++ compilers are competitive these days (albeit with compiler development teams an order of magnitude larger than the corresponding Fortran ones). Fortran also has many modern features which are still lacking in most mainstream languages, for example partitioned global-address space (coarrays). 

I don't see much incentive to move the millions of lines of Fortran into another language, but what is becoming increasingly common is to develop a high-level software layer in something else, usually Python, which allows more rapid prototyping and development, whilst keeping all the numerically-intensive work in Fortran or C++.

I'm confused about your Mac M1 chipset reference; how does this relate to your Fortran question? There are good ARM Fortran compilers, if that's what you're worried about. 

All the best,

Phil Hasnip

------------------------------------------------------------------------------------
Dr Phil Hasnip                  Email: phil.hasnip**york.ac.uk
EPSRC RSE Fellow         Web:  www-users.york.ac.uk/~pjh503
Dept of Physics
University of York             Tel:     +44 (0)1904 322225
York YO10 5DD


On Thu, 10 Jun 2021 at 01:58, Joe Leonard jleonard42%x%gmail.com <owner-chemistry**ccl.net> wrote:
Folks, are there QM packages that have managed to “lose” all their fortran code or are new enough to have been developed in a different language or different languages?  I have not seen good comments re: the Mac M1 chipset and I’m curious whether there are alternatives…

I’m sure others would be interested as well.

Joe Leonard
"Peter Thiel was right, we just can't build cool sh*t anymore. I really did want a flying car, and all I have is 140 characters and promises of AI that never come true."