Re: [avr-libc-dev] Some question regarding FP-math

[Dmitry]

18.06.2012 18:53, Dr. Alexander Klein:
[...]
> 1. Most if not all transcendental functions are implemented as power
> series approximations, but no hints are given as to their properties
> of approximation. Are the polynomials or maybe their derivatives
> optimal in any L_p-sense? Can a description be found anywhere?
Main reason was the flash usage minimization. Minor reason was a
fast multiplication: avoid division.

> 2. All we have for the time being is single precision float. Are the
> functions for power series evaluation optimised so as to minimise
> summation error?
A part of internal calculations is more precision: 32-wide mantissa is
used.

> 3. In an old post
> (http://lists.nongnu.org/archive/html/avr-libc-dev/2006-04/msg00068.html)
> someone benchmarked basic arithmetic operations, but only for one
> platform. How do other platforms perform? Especially, would it be
> worthwhile to try to speed up multiplication?
The avr-libc documention contains a good set of benchmarks. The big
difference between avr2 and avr4 is due to multiplication.

Regards,
Dmitry.