Re: Calling conventions (particularly 32-bit ARM)

On Tue, 14 Jan 2025 19:39:06 +0100
Terje Mathisen <terje.mathisen@tmsw.no> wrote:

 
It is much more likely that we will simply switch to quad/f128 (or
even arbitrary precision) for those few computations that could need
it.
 
Terje
 

I had one of those computations that can benefit from quad and, may be,
from octal precision yesterday/today.
Design of equiripple symmetric FIR filter with ~2000 coefficients (more
commonly called taps) using Parks-McClellan method. Implemented by
Matlab/Octave function that traditionally was called remez and now
called firpm. I suppose, the new name was invented, because the
algorithm is only similar to Remez exchange, but differs in details.

Octave failed to do it claiming of limited precision of arithmetic as a
reason.

In Matlab implementation is better, and it was able to create filter
with ~1800 taps, which happened to be sufficient for my today's needs.
But even Matlab was unable to cope with 2000 taps.

If I had more time, I'd try to implement Parks-McClellan algorithm
myself, to see bottlenecks and see whether higher precision helps a
lot, or just a little. Unfortunately, right now I am too busy with work.