[Numpy-discussion] Comment published in Nature Astronomy about The ecological impact of computing with Python

PIERRE AUGIER pierre.augier at univ-grenoble-alpes.fr
Tue Jan 26 09:59:33 EST 2021


Here are some preliminary results of an experiment on energy consumption measurement at Grid'5000 (https://www.grid5000.fr/w/Energy_consumption_monitoring_tutorial). The goal is to have enough to be able to submit a serious comment to a recent article published in Nature Astronomy (Zwart, 2020) which recommends to stop using and teaching Python because of the ecological impact of computing.

On the attached figure: it represents the CO2 production as a function of elapsed time for different implementations (https://github.com/paugier/nbabel). It can be compared with https://raw.githubusercontent.com/paugier/nbabel/master/py/fig/fig_ecolo_impact_transonic.png taken from Zwart (2020).

The implementations labeled "nbabel.org" have been found on https://www.nbabel.org/ and have recently been used in the article by Zwart (2020). Note that these C++, Fortran and Julia implementations are not well optimized. However, I think they are representative of many C++, Fortran and Julia codes written by scientists.

There is one simple Pythran implementation which is really fast (slightly slower than the fastest implementation in Julia but it is not a big deal).

Note that of course these results do not show that Python is faster that C++!! We just show here that it's easy to write in Python **very** efficient implementations of numerically intensive problems.

I think soon I'm going to have enough materials to contact the editors to ask how we can publicly answer to this comment published in their journal. With this work https://github.com/paugier/nbabel (proper energy consumption measurements), I clearly demonstrate that the basis of Zwart's comment is factually wrong (its benchmark and Figure 3), so that most of its conclusions are also wrong.

I'd like to know if some people involved in the community are willing to be co-authors of this potential reply.


Pierre Augier - CR CNRS                 http://www.legi.grenoble-inp.fr
LEGI (UMR 5519) Laboratoire des Ecoulements Geophysiques et Industriels
BP53, 38041 Grenoble Cedex, France                tel:+

----- Mail original -----
> De: "PIERRE AUGIER" <pierre.augier at univ-grenoble-alpes.fr>
> À: "numpy-discussion" <numpy-discussion at python.org>
> Envoyé: Mardi 24 Novembre 2020 16:47:05
> Objet: [Numpy-discussion] Comment published in Nature Astronomy about The ecological impact of computing with Python

> Hi,
> I recently took a bit of time to study the comment "The ecological impact of
> high-performance computing in astrophysics" published in Nature Astronomy
> (Zwart, 2020, https://www.nature.com/articles/s41550-020-1208-y,
> https://arxiv.org/pdf/2009.11295.pdf), where it is stated that "Best however,
> for the environment is to abandon Python for a more environmentally friendly
> (compiled) programming language.".
> I wrote a simple Python-Numpy implementation of the problem used for this study
> (https://www.nbabel.org) and, accelerated by Transonic-Pythran, it's very
> efficient. Here are some numbers (elapsed times in s, smaller is better):
>| # particles |  Py | C++ | Fortran | Julia |
>|     1024    |  29 |  55 |   41    |   45  |
>|     2048    | 123 | 231 |  166    |  173  |
> The code and a modified figure are here: https://github.com/paugier/nbabel
> (There is no check on the results for https://www.nbabel.org, so one still has
> to be very careful.)
> I think that the Numpy community should spend a bit of energy to show what can
> be done with the existing tools to get very high performance (and low CO2
> production) with Python. This work could be the basis of a serious reply to the
> comment by Zwart (2020).
> Unfortunately the Python solution in https://www.nbabel.org is very bad in terms
> of performance (and therefore CO2 production). It is also true for most of the
> Python solutions for the Computer Language Benchmarks Game in
> https://benchmarksgame-team.pages.debian.net/benchmarksgame/ (codes here
> https://salsa.debian.org/benchmarksgame-team/benchmarksgame#what-else).
> We could try to fix this so that people see that in many cases, it is not
> necessary to "abandon Python for a more environmentally friendly (compiled)
> programming language". One of the longest and hardest task would be to
> implement the different cases of the Computer Language Benchmarks Game in
> standard and modern Python-Numpy. Then, optimizing and accelerating such code
> should be doable and we should be able to get very good performance at least
> for some cases. Good news for this project, (i) the first point can be done by
> anyone with good knowledge in Python-Numpy (many potential workers), (ii) for
> some cases, there are already good Python implementations and (iii) the work
> can easily be parallelized.
> It is not a criticism, but the (beautiful and very nice) new Numpy website
> https://numpy.org/ is not very convincing in terms of performance. It's written
> "Performant The core of NumPy is well-optimized C code. Enjoy the flexibility
> of Python with the speed of compiled code." It's true that the core of Numpy is
> well-optimized C code but to seriously compete with C++, Fortran or Julia in
> terms of numerical performance, one needs to use other tools to move the
> compiled-interpreted boundary outside the hot loops. So it could be reasonable
> to mention such tools (in particular Numba, Pythran, Cython and Transonic).
> Is there already something planned to answer to Zwart (2020)?
> Any opinions or suggestions on this potential project?
> Pierre
> PS: Of course, alternative Python interpreters (PyPy, GraalPython, Pyjion,
> Pyston, etc.) could also be used, especially if HPy
> (https://github.com/hpyproject/hpy) is successful (C core of Numpy written in
> HPy, Cython able to produce HPy code, etc.). However, I tend to be a bit
> skeptical in the ability of such technologies to reach very high performance
> for low-level Numpy code (performance that can be reached by replacing whole
> Python functions with optimized compiled code). Of course, I hope I'm wrong!
> IMHO, it does not remove the need for a successful HPy!
> --
> Pierre Augier - CR CNRS                 http://www.legi.grenoble-inp.fr
> LEGI (UMR 5519) Laboratoire des Ecoulements Geophysiques et Industriels
> BP53, 38041 Grenoble Cedex, France                tel:+
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> NumPy-Discussion mailing list
> NumPy-Discussion at python.org
> https://mail.python.org/mailman/listinfo/numpy-discussion
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