[racket] Perlin and simplex noise - optimizing Racket code

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Thu Apr 11 15:24:27 EDT 2013

Just based on past experience and not a careful look at your code, I think
that it is safe to say that TR is the way to go here. That's going to have
the best bang for your buck as a tradeoff of simple-to-do vs spedup-gained.


On Thu, Apr 11, 2013 at 12:07 PM, JP Verkamp <racket at jverkamp.com> wrote:

> Partially out of curiosity and partially in my ongoing quest to try out
> game development in Racket, I've implemented a pure Racket version each for
> Perlin and simplex noise. It's pretty much a direct translation of the code
> from this PDF, originally in C:
> http://webstaff.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
> Here is a blog post with some pretty pictures but little actual code:
> http://blog.jverkamp.com/2013/04/11/perlin-and-simplex-noise-in-racket/
> Here's just the code:
> https://github.com/jpverkamp/noise
> It's definitely not pure / functional, but I think it's relatively easy to
> read (or as easy as noise functions can be).
> What I'm wondering though is if someone with a bit more experience in
> optimizing Racket code could take a look at it. I know that it should be
> possible to get a bit more speed; it's almost all number crunching, mostly
> floating point math but with a few integer only bits (those are causing the
> most trouble...). At the moment, I can think of at least three routes for
> optimization although I'm probably missing something:
> - using (racket/floum) -- I've tried just blindly replacing * + - / with
> fl* fl+ fl- fl/ (and fixing the numerous errors that crop up), but it
> doesn't seem to result in much of a speedup at all. I think that this is a
> combination of still requiring runtime checks on the values and having to
> convert between exact/inexact, but I'm not sure.
> - using Typed Racket -- Theoretically this will allow the compiler to
> choose the correct functions as above and avoid having to do any runtime
> checks at all, although I'm not sure how much of that has been implemented.
> - using the FFI to bind to a native C interface -- This would probably be
> the fastest in the end, but I'd like to do as much in pure Racket as I can
> for the time being (although it would be interesting to learn how to do
> this). Not to mention that a part of me rejects that it wouldn't be
> possible for Racket to at least match C code in a perfect world.
> Right now the code takes about 1-2 seconds to generate a 256x256 image.
> Optimally, that should run in near realtime, although I would be happy just
> getting it into the tens or even hundreds of ms range. A part of that time
> is turning the noise into a color (for testing), but even without that it
> still takes about 1 second on my machine for simplex noise.
> Thanks for any feedback!
> JP
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