14 Nov
2010
14 Nov
'10
12:37 p.m.
On Sun, Nov 14, 2010 at 06:14:48AM +0100, Ralf Mardorf wrote:
Using sin/cos still is very time-consuming?
Define 'very time consuming'.
I do understand The Wiki on German better, but the
Wiki on English,
pardon:
"Die Tabellierung aller Werte ist angezeigt bei
geschwindigkeitskritischen Echtzeit-Anwendungen, wenn diese nur eine
recht kleine Winkelauflösung
benötigen." (http://de.wikipedia.org/wiki/Sinus_und_Kosinus#Berechnung)
Loosely translated: Tabulation for rt (when using sin/cos) for small
angles (what ever a small angle might be) is still faster.
This is not about small angles. More exactly: 'Tabulation is the proper
solution for RT applications when only low resolution of the angle is
required'.
You won't get a single simple answer to a question that has
no such answer. It all depends on:
* The platform. DSP chips don't usually have fast sin() and
cos() functions while on a modern PC these can be quite
fast.
* The application: which will define what is required in
terms of
- absolute accuracy
- relative accuracy
- resolution
- other numerical criteria
* How the calculation is used:
- for each sample
- for each N-th sample
- for each N-th sample but only when the input changes
and
- on one or a few channels, or
- maybe on hundreds of them.
Ciao,
--
FA
There are three of them, and Alleline.