3 Jan
2012
3 Jan
'12
3:51 a.m.
On Mon, Jan 02, 2012 at 09:30:56PM -0500, Paul Davis wrote:
On Mon, Jan 2, 2012 at 9:17 PM, Fons Adriaensen
<fons(a)linuxaudio.org> wrote:
Again I don't agree these are two different issues.
'Taking care of (2)' may avoid the slowdown, but it may also
hide the real problem, which is that you are trying to do a
computation that is beyond the limits of what the FPU can do.
And that problem is *not* solved by ensuring there will be
no slowdown. In some cases replacing small values (of which
denormals are just one form) by zero or adding a small bias
may help. In other cases it doesn't and it just produces new
problems. Such a method is no substitute for analysis, not any
more than blindly changing floats into doubles and hoping for
the best.
Ciao,
--
FA
Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.
I don't agree with blaming the Intel
architecture. Denormals are
just one tiny aspect of a much wider issue which is numerical
precision and stability, and that affects all architectures.
Anyone writing numerical or DSP code should be aware of this
and be able to analyse the algorithm. You don't produce good
numerical or DSP code by blindly implementing textbook equations.
absolutely.
but there are two aspects to this issue:
(1) good numerical or DSP code
(2) not slowing the processor down by a factor of 10 or more
non-Intel architectures took care of (2), while leaving (1) for the
programmer to tackle.