Re: [fluid-dev] problems with fluidsynth 1.1.6 on a raspberry pi

[David Henningsson]

On 11/18/2012 07:56 PM, Pedro Lopez-Cabanillas wrote:
> El Domingo, 18 de noviembre de 2012 12:51:58 David Henningsson escribió:
> > I'll do some experiments with it when I have some more time.
>
> My bet is floating point exceptions.

I tried to verify this theory on my Nexus 7 device. I've tried to 
compile with -ffast-math, with according to documentation should 
activate flush-to-zero mode, as well as activating it explicitly with 
this code:

  asm(
    "vmrs r10, FPSCR \n"
    "orr r10, r10, #0x01000000 \n"
    "vmsr FPSCR, r10 \n"
  );

...but this did not give a notable performance difference.

I also compared double vs single precision floats, and singles were 
somewhat faster.

My test scenario was this command line:

time fluidsynth -F /tmp/result.wav -z 4096 
/usr/share/sounds/sf2/FluidR3_GM.sf2 ~/Downloads/NIGHTSIN.KAR

Doubles: 81 seconds
Singles: 65 seconds
...so about 20% faster.

I also ran it with perf. Here are the top five results:

Doubles:
    31.86%      24682     fluid_rvoice_dsp_interpolate_4th_order
    29.41%      22568     fluid_rvoice_buffers_mix
    14.81%      11418     fluid_iir_filter_apply
     9.01%       6952     fluid_revmodel_processmix
     3.31%       2568     fluid_rvoice_write

Singles:
    34.70%      21826     fluid_rvoice_dsp_interpolate_4th_order
    24.55%      15519     fluid_rvoice_buffers_mix
    15.00%       9506     fluid_iir_filter_apply
     9.21%       5837     fluid_revmodel_processmix
     3.76%       2297     fluid_rvoice_write

// David