[PD] [bob~] denormals issue?

[Christof Ressi]

Hi Katja, 

> Even if your test reveals a beneficial effect from compiler flags, 
> it is better when denormals are detected and flushed in the C code.

definitely! Maybe using the PD_BIGORSMALL macro on each filter state at the end of the DSP routine does the trick, just like in all the other recursive filters in Pd.



> Von: katja <katjavetter at gmail.com>
> An: "Christof Ressi" <christof.ressi at gmx.at>
> Cc: pd-list <pd-list at iem.at>, "Miller Puckette" <msp at ucsd.edu>
> Betreff: Re: [PD] [bob~] denormals issue?
>
> Hi Christof,
> 
> Makefile.pdlibbuilder passes flags '-march=pentium4 -msse -msse2
> -mfpmath=sse' for optimization to the compiler on Windows. You could
> try compiling without (some of) these flags to see if they are
> responsible for the different behavior. Makefile-defined optimization
> flags can be overriden with argument CFLAGS given on command line.
> 
> The effect of optimization flags on denormals varies per processor
> type, unfortunately. When we had denormals on Raspberry Pi ARMv6 they
> wouldn't go away no matter what flags, is what I remember. Even if
> your test reveals a beneficial effect from compiler flags, it is
> better when denormals are detected and flushed in the C code. Anyway,
> it is still interesting to know what makes the difference.
> 
> Katja
> 
> On Wed, Sep 21, 2016 at 12:32 AM, Christof Ressi <christof.ressi at gmx.at> wrote:
> > Hmmm... I compiled [bob~] myself with MinGW and pd-lib-builder and I noticed two things:
> > 1) the CPU rise is gone
> > 2) it needs only half the CPU. I put 20 [bob~] objects in a switched subpatch and measured the CPU load. The DLL which comes with the Windows binaries needs 15%, while my own DLL needs only 7%! That's quite a deal...
> >
> > Christof
> >
> > PS: I attached the DLL in case you wanna try it yourself.
> >
> >
> >> Gesendet: Samstag, 17. September 2016 um 22:58 Uhr
> >> Von: "Christof Ressi" <christof.ressi at gmx.at>
> >> An: pd-list at iem.at, "Miller Puckette" <msp at ucsd.edu>
> >> Betreff: [PD] [bob~] denormals issue?
> >>
> >> Hi Miller,
> >>
> >> feeding audio into [bob~] and then going to zero will increase the CPU load by ca. 6%. Clearing the filter or adding a tiny amount of noise brings the CPU load back to its usual level immediately, so I guess it's a problem with denormals.
> >> My Pd load meter won't really show the increase, but it's clearly visibly on Process Explorer.
> >>
> >> See my attached patch. Tried with Pd 0.47.1, Lenovo Thinkpad L440, Windows 7.
> >>
> >> Christof_______________________________________________
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> >>
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