On Sun, 2 Jan 2011, Stephen Tetley wrote:
Un-optimized, with a head-strict stream (basically Wouter Swierstra's Stream with a bang on the element), rendering currently takes minutes to generate seconds. But as well as the Stream representation, I've plenty of room to optimize the WAV file generation.
Using stream-fusion:Stream rendered to a low-level list representation you get relatively efficient computation. I used my signal generator type and StorableVector.Lazy in order to perform this one in real-time: http://www.youtube.com/watch?v=KA6DE9jlpSY (see packages synthesizer-core and synthesizer-alsa) That is, even interactive realtime processing is possible, but not very complex one. It requires very disciplined programming and after a small change to your program the GHC optimizer may decide to compile it completely different and the program becomes five times slower. I have also written an overview of what data structures are useful for what signal processing purpose: http://hackage.haskell.org/packages/archive/synthesizer/0.2.0.1/doc/html/Syn...
Probably I can live without definitions like @ ones = 1 <:> ones @, I would like to know whether of not this is impossible with Stream-Fusion anyway.
The recursive style allows for elegant writing of feedback, solution of differential (e.g. oscillation) equations. It's sad, but I think you cannot have it with stream-fusion. Maybe in future GHC or JHC get more cleverness to eliminate even more lazy values. For feedback with longer and constant delay, you might buffer the data in a chunky storable vector and then get efficient recursive computation.