Re: Python for Fortran programmers
- From: Paul Van Delst <Paul.vanDelst@xxxxxxxx>
- Date: Wed, 15 Feb 2006 15:00:58 -0500
Michael Tobis has posted an essay in comp.lang.python regarding "the
proposition for Python in the Fortran community", which I am reposting
here. He said he wants feeback.
I think a scripting language such as Python is a good complement to a
compiled language such as Fortran or C++, but I would still prefer to
have the "guts" of a computationally intensive program in Fortran,
because of speed, finer control (Fortran KIND's for example), and the
greater number of programming errors that are typically detected by a
good compiler vs. an interpreter.
Here is his essay.
What's his point? "Python is great so let's all use it" ?
He mentioned the things that Fortran is ill-suited for (not actually describing them for non-CS folks. "distributed control and ensemble management" ?? What does that mean?) but I didn't see much in his list that is particularly Fortran-specific. I mean, "source and version control"? What does that have to do with Fortran? You'd have the same issue with Python; or <insert language of choice>. My experience with source control has been that the biggest weakness is the people using it (or not as the case may be), not the method employed.
And there was no analysis of the balance between his mentioned pros (high performance and
flexibility in dealing with regular arrays, backward compatibility with the existing code base, and the familiarity with the language among the modeling community) and cons (source and version control and audit trails for runs, build system management, test specification,etc..) Should we weight them all equally? Should all involved disciplines weight them the same way?
As to the ad hoc deployment - when you (figuratively) throw 1000's of people together to work on something (such as a climate model) and those people are spread across the globe, work for instituitions that typically have very different goals (even *within* agencies), and are funded based on who-knows-what criteria, and -- assuming the grand master plan poobah is prescient enough to forsee all the issues that will crop up along the way -- then good luck trying to come up with a plan for "ad-hoc deployment prevention" upon which everybody involved can agree. More often than not single viewpoints will dominate (Did somebody say security?)
I absolutely agree with his comments about unit and integration testing. But no real info was put forth on how Python can help solve this problem. Will python help design the test parameters and write the test code?
A rather bland series of paragraphs, IMO. It reads like either a) a funding proposal [hence all the interspersed buzzwords and jargon to make managers get all excited] or b) an undergraduate CS assignment.
Now, you'll have to excuse me while I go back to studying PHP/MySQL. It's going to solve all my problems I'm told.... :o)
The established use of Fortran in continuum models such as climate
models has some benefits, including very high performance and
flexibility in dealing with regular arrays, backward compatibility with
the existing code base, and the familiarity with the language among the
modeling community. Fortran 90 and later versions have taken many of
the lessons of object oriented programming and adapted them so that
logical separation of modules is supported, allowing for more effective
development of large systems. However, there are many purposes to which
Fortran is ill-suited which are increasingly part of the modeling
These include: source and version control and audit trails for runs,
build system management, test specification, deployment testing (across
multiple platforms), post-processing analysis, run-time and
asynchronous visualization, distributed control and ensemble
management. To achieve these goals, a combination of shell scripts,
specialized build tools, specialized applications written in several
object-oriented languages, and various web and network deployment
strategies have been deployed in an ad hoc manner. Not only has much
duplication of effort occurred, a great deal of struggling up the
learning curves of various technologies has been required as one need
or another has been addressed in various ad hoc ways.
A new need arises as the ambitions of physical modeling increase; this
is the rapid prototyping and testing of new model components. As the
number of possible configurations of a model increases, the expense and
difficulty of both unit testing and integration testing becomes more
Fortunately, there is Python. Python is a very flexible language that
has captured the enthusiasm of commercial and scientific programmers
alike. The perception of Python programmers coming from almost any
other language is that they are suddenly dramatically several times
more productive than previously, in terms of functionality delivered
per unit of programmer time.
One slogan of the Python community is that the language "fits your
brain". Why this might be the case is an interesting question. There
are no startling computer science breakthroughs original to the
language, Rather, Python afficionados will claim that the language
combines the best features of such various languages as Lisp, Perl,
Java, and Matlab. Eschewing allegiance to a specific theory of how to
program, Python's design instead offers the best practices from many
other software cultures.
The synergies among these programming modes is in some ways harder to
explain than to experience. The Python novice may nevertheless observe
that a single language can take the place of shell scripts, makefiles,
desktop computation environments, compiled languages to build GUIs, and
scripting languages to build web interfaces. In addition, Python is
useful as a wrapper for Fortran modules, facilitating the
implementation of true test-driven design processes in Fortran models.
Another Python advocacy slogan is "batteries included". The point here
is that (in part because Python is dramatically easier to write than
other languages) there is a very broad range of very powerful standard
libraries that make many tasks which are difficult in other languages
astonishingly easy in Python. For instance, drawing upon the standard
libraries (no additional download required) a portable webserver
(runnable on both Microsoft and Unix-based platforms) can be
implemented in seven lines of code. (See
http://effbot.org/librarybook/simplehttpserver.htm ) Installation of
pure python packages is also very easy, and installation of mixed
language products with a Python component is generally not
significantly harder than a comparable product with no Python
Among the Python components and Python bindings of special interest to
scientists are the elegant and powerful matplotlib plotting package,
which began by emulating and now surpasses the plotting features of
Matlab, SWIG, which allows for runtime interoperability with various
languages, f2py which specifically interoperates with Fortran, NetCDF
libraries (which cope with NetCDF files with dramatically less fuss
than the standard C or Fortran bindings), statistics packages including
bindings to the R language, linear algebra packages, various
platform-specific and portable GUI libraries, genetic algorithms,
optimization libraries, and bindings for high performance differential
equation solvers (notably, using the Argonne National Laboratory
package PetSC). An especially interesting Python trick for runtime
visualization in models that were not designed to support it, pioneered
by David Beazley's SWILL, embeds a web server in your model code.
See especially http://starship.python.net/~hinsen/ScientificPython/ and
http://scipy.org as good starting points to learn about scientific uses
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
- Python for Fortran programmers
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