[PlanetCCRMA] Pentium-4 and denormal numbers on planetccrma

andersvi@extern.uio.no andersvi@extern.uio.no
Wed Jan 12 02:59:01 2005

I see in the list-archives there has been issues around denormal
numbers, but it seems limitied to the ladspa tap-plugin.

Recently found that planetccrma's dist of pd & externals gave
some trouble related to "denormal numbers" on a pentium-4 based
laptop here.

Problem was it went up to 90+% cpu, and stayed there, while same
patch on athlon-based machine (half the speed) ran at 20%.

It seems that these numbers - very small numbers - are optimized
to zero automatically on some cpu's, while others, like my
P4-based here, need special handling when compiling apps.

The fix was to recompile pd and the percolate-lib with

  -mcpu=pentium4 -mfpmath=sse -msse

included in CFLAGS (not sure whether "-mcpu=pentium4" actually
was necessary).

Ive started recompiling various externals and other things with
the flags included.  Im not sure, but wouldnt this be a problem
with all apps running loops calculating numbers around zero
somewhere.  Would it be a solution to compile coming upgrades at
planetccrma with these same flags?