[Kstars-devel] Plans for threading in KStars

[Alexey Khudyakov]

On 30.10.2011 23:30, Akarsh Simha wrote:
> So the idea is that DeepStarComponent::draw() will trigger the worker
> thread to start recalculating positions (EquatorialToHorizontal() is
> the slowest call),

I didn't read your mail thoroughly. But there is one thing that caught 
my attention:

EquatorialToHorizontal call contains 3 sincos calls and 1 cos, asin and 
acos call each. It's looks quite costly. But effectively it is just 
transformation between different reference frames and simply a rotation.

I suppose that representation of point on sphere as two angles doesn't 
admit effificent rotation. But this is the case where quaternions should 
shine. In this case rotation is just multiplication by another quaternion.

There is a lot food for thoughts. What is best representation of point 
on sphere? Are quaternions right solution? If they are how should we 
deal with addition degeneracy? (We have 2 degrees of freedom and unit 
quaternions which could represesent rotations have 3). Do we have class 
set up right? (I think we are not)


Could you put your profiling results somewhere? I'd like to look at them.