[Kstars-devel] Binary file format for NOMAD

[James Bowlin]

On Tue July 15 2008, Akarsh Simha wrote:
> Yes. What I plan is to check for NOMAD, just like how we check for
> Tycho-2 deepstars.dat currently. NOMAD could sit in a level-8 mesh
> while Tycho-2 remains in a level-5 mesh.

Brilliant!  I was hoping you would be able to implement multiple meshes
this summer.

A level-8 mesh might be overkill for NOMAD if it is all going on one 
mesh. 

 level  trixels
 -----  -------
   3       512
   4        2K
   5        8K
   6       32K
   7      128K
   8      512K
   9        2M
  10        8M

The downside to large meshes is the overhead for all the empty 
StarBlockLists and also the number of disk seeks required when the 
finer mesh first kicks in.

If you implement sparse indexes (using a QHash instead of a QVector
to hold the StarBLockLists) and put NOMAD itself on multiple meshes at, 
for example, 10e6, 100e6, and 1e9 stars, both these problems are 
solved.  You could probably get to one *billion* stars this summer 
[requisite pinky finger to side of mouth].

Tuning how many stars we put on what mesh levels is an interesting 
problem.  The answer might depend upon what star densities we expect
to be used most.  


-- 
Peace, James