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

From: David Henningsson
Subject: Re: [fluid-dev] problems with fluidsynth 1.1.6 on a raspberry pi
Date: Mon, 19 Nov 2012 06:42:38 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2

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:

    "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:

    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

    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

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