[PD] Hunting denormals?

[Miller Puckette]

Hi all,

Looking into this once again (I've had this problem for 10 years or more
now) I just found out that gcc has a -ffast-math flag that prevents denormals
for slowing the code down, as long as the CPU has SSE instructions.  I
don't know if the geode does or not, though!

On linux, at any rate, you can type 
CFLAGS="-ffast-math -O6" ./configure

at the appropriate moment when compiling Pd.  I'm not sure how this will spin
out in Windows, though.

Pd code is shot through with special tests to try to catch floating point
operations to prevent them from making denormals, but apparently I haven't
found every possible way they can come up.

cheers
Miller

On Sun, Nov 02, 2008 at 10:07:13PM +0000, errordeveloper at gmail.com wrote:
> On Fri, Oct 31, 2008 at 04:27:08PM -0400, Bill Gribble wrote:
> > I have a patch of medium complexity, with a handful of instruments~ and
> > a bunch of sequencing and arranging-type message handling.  On my speedy
> > Intel laptop it has no problem and barely notches the CPU usage.
> > However, when I run this patch on my teeny Geode-based UMPC it pegs CPU
> > at 100%. 
> i wouldn't expect a lot from a geode machine ;))
> > 
> > I'm pretty sure this is a denormal issue.  There are a grand total of
> > maybe 5 noise~, 5 osc~, 10 vline~, 5 lop~, and 1 delay line in the whole
> > patch and not much else besides message processing... I wouldn't guess
> > this to run me out of compute power. 
> pardon, but what the word 'denormals' means? ..never heard it
> > 
> > Any hints on how to isolate where the denormals might be popping up?  I
> > have looked for signal processing loops, and the only ones I create are
> > around the delayline (feedback) and I suppose in the iir implementation
> > of the lop~.  
> > 
> > Any help appreciated, 
> > Bill Gribble
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
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