What other programming projects teach me about performance

By Serdar Yegulalp | 2016/07/07 08:00

MeTal is far from my only programming project, although it's probably the most significant. One of the other things I've been dabbling in is a recreation of a classic 1980s arcade game, also in Python. Working on it has provided me with some perspectives about the much-discussed issue of Python performance.

Some things become plain when you write games or other performance-intensive applications in Python vs., say, C/C++:

  1. You inevitably trade performance across the board for convenience.
  2. You can gain back a lot of that performance, but not all of it.
  3. How much you gain back is largely a matter of what you, the programmer, are comfortable with, and not necessarily a technical barrier.

The last of these three is, I think, the most important issue and also the most underappreciated one. While working on Robotron, I was able to get performance that was pretty respectable on modern hardware -- between 1% and 2%, sometimes a tot more, on my 8-core desktop, and between 5-8% on my quad-core notebook (vintage 2012). On my slow-as-frozen-molasses HP Stream 11, with a whopping TWO cores, I got 25-30% -- but at least it ran, and it even maintained framerate.

For perspective, Crossy Road runs on the desktop at about 3-6% CPU.

For additional perspective, Robotron originally ran at something like 25% CPU, sometimes even more than that, on the notebook. I was able to shave it down not by doing any one thing, but by way of a whole mess of things:

There's only so much speedup you can get from these tricks, before the overhead of the Python interpreter itself starts becoming the real barrier.

Now, for all I know, there may well be other things that provide even more speedup. I haven't tried PyPy, for instance, if only because it doesn't work very well with this project (yet), and when I tried an earlier build of Nuitka, it gave me results that were far worse than my own hand-optimized build. All of those avenues may well yield better results in the future.

If I had written the whole thing in C/C++, with something like Allegro or SDL2, I would easily have seen a 10x boost in speed, if not more. But that, too would have come at multiple costs:

All programming is about choosing between tradeoffs. For me, development comfort matters; I don't like C/C++ syntax, and Python is just easier for me to work with and reason about. I do plan on getting more C/C++ under my belt over time, though -- just as a way to see where knowing all that takes me. But for now, Python and I are tightly knit.

Tags: Python performance programming

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