[sdiy] Raspberry Pi 2 Synthesizer Project

[Barry Klein]

Warning... I don't know DSP or what I'm talking about but dspconcepts.com's Audioweaver uses Neon on rpi. You might just call them for tips....

Sent from my iPhone

> On Feb 10, 2016, at 4:32 PM, Scott Gravenhorst <music.maker at gte.net> wrote:
> 
> Regarding NEON...
> 
> I'm using gcc version 5.3.0 (and I'm compiling on the Rpi2 itself).
> 
> The configuration is set --with-float=hard.
> 
> I did some experiments and noticed that when gcc is used with -S (and no -o) it will generate a .s file with assembly instructions.  One can see NEON instructions in the output file (such as vadd.f32).  Apparently, this installation of gcc (on my Rpi2) is configured to default to using hardware floating point since without any special or additional switches it will generate NEON instructions.  I also tried to use the NEON intrinsics which worked, but was somewhat slower than letting the compiler vectorize and implement the algorithm.  I tested using a simple single pole low pass IIR filter.  I managed to turn off NEON and the output code was about 5 times slower.
> 
> --ScottG
> 
> 
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