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Date: Mon, 12 May 2014 15:41:17 +1000
Subject: Re: Using threads for audio computing?
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:71371

On Mon, May 12, 2014 at 3:33 PM, lgabiot <lgabiot@hotmail.com> wrote:
> But AFAIK the python GIL (and in smaller or older computers that have only
> one core) does not permit true paralell execution of two threads. I believe
> it is quite like the way multiple processes are handled by an OS on a single
> CPU computer: process A has x CPU cycles, then process B has y CPU cycles,
> etc...
> So in my case, I must have a way to make sure that:
> thread 1 (which gets audio from Pyaudio and put() it in the Queue) is not
> interrupted long enough to miss a sample.
> If I suppose a worst case scenario for the computer, like a raspberry-pi,
> the CPU speed is 700MHz, which gives approx 14 000 CPU cycles between each
> audio samples (at 48 kHz FS). I don't know if 14 000 CPU cycle is a lot or
> not for the tasks at hands.
>
> Well, at least, it is what I understand, but since I'm really both a
> beginner and an hobbyist, I might be totally wrong...

The GIL is almost completely insignificant here. One of your threads
will be blocked practically the whole time (waiting for more samples;
collecting them into a numpy array doesn't take long), and the other
is, if I understand correctly, spending most of its time inside numpy,
which releases the GIL. You should be able to thread just fine.

ChrisA