[Kstars-devel] profiling KStars

[James Bowlin]

On Tuesday 23 May 2006 12:27 pm, Jason Harris wrote:
> I've begun to work on trying to speed KStars up a bit.

Both projects sound very exciting.  In addition to HTM and kd-trees
there are other spatial indexes such as r-trees but I think that HTM
will be the way to go because it is optimized for the special case
where all the objects are on the surface of a sphere.  The beauty of
HTM is that the index of each object is fixed and totally independent
of the other objects in the data set.  With kd-trees and r-trees the
resulting index is data-dependent which can slow things down.  The
HTM is like a generalization of kd-trees applied to the special case
of the surface of a sphere.  It is a generalization because it is not
exactly a "binary space partitioning"  because it is not binary but
it is a space (surface) partitioning.

This leads to my first question:  I know there are parameters in the
HIP files that deal with the drift of stars on the celestial sphere.
How often are the positions of the stars recalculated?  The spatial
index will have to be recalculated/re-adjusted whenever these positions
are updated so the frequency of these updates will affect design decisions.


On Tuesday 23 May 2006 12:27 pm, Jason Harris wrote:
> Maybe we  could also store objects in a hierarchical list structure
> that mimics the HTM, which would allow us to skip entire sections of
> objects based on their position within the tree.

Yes.  The main benefit of HTM and other spatial indexes is achieved by
storing the objects in the index.


I am interested in working on both projects suggested.  The indexing
project is the most exciting to me but getting rid of unneeded
transcendental function calls is always a good/fun thing too.

I'm trying to install qt4, kde4, etc. now.  I found Jason's "QT4 Pep
Talk" in this mailing list but I still don't know how to install
kdelibs4_snapshot.  I found the kdelibs4_snapshot section of the KDE
source repository but even the INSTALL and README files there did not
discuss downloading and where I should put things and how not to break
my current KDE, etc.

If I can get kstars-4 up and running, I would like to try putting the
HIP stars into an HTM, unless someone else is already working on this
or there is something better for me to be doing.


-- 
Peace, James