[sdiy] Raspberry Pi 2 Synthesizer Project

[ASSI]

On Sunday 07 February 2016, 08:27:14, Scott Gravenhorst wrote:
> Achim wrote this:
>  >For that kind of code it should be beneficial to use VFPv4 and NEONv2,
>  >which is available on the Pi2.
> 
> Yes, I saw that NEON is in the IC, but I need to research how to turn it
> on with gcc as I believe it is not used by default.

You need something like
 -mcpu=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard
for this.

> It would be interesting to see if there's much of a difference.

The point of the exercise is to use the NEON engine in parallel to the rest 
of your code.  If you do this right, you suddenly have lots of free cycles 
for other things.

> In the past, all of
> my synth designs (such as for dsPIC and FPGA) have used fixed point
> format.  This particular synth uses the sin() function with uses double
> float arithmetic.  Voice summing is done with fixed pt.  A future KS
> synth will be float or double at first and then converted to fixed point
> just to see if there's a significant difference.

Unless you manage to use both fixed-point and floating-point in parallel, 
you're likely going to be disappointed.  Again, to wring out the most 
performance, you need to make simultaneous use of all function units (and 
keep them fed with data).


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Waldorf MIDI Implementation & additional documentation:
http://Synth.Stromeko.net/Downloads.html#WaldorfDocs