Updates to IC generation routines in utils/ICs

[The9Cat]

Summary of changes

• Added a new routine, addring to generate a phase-space torus of material with a Gaussian velocity dispersion given a spherical halo model
• Fixed an error in the AxiSymModel:gen_point routine for particles at a given radius. This was not previously used by gensph.
• Updated AxiSymModel::gen_point routines to support new quiet-start methods implemented in gensph. These include distributing particles on a spherical position 'grid', distributing particles on a spherical position and velocity grid, Sellwood's quiet-start orbital plane algorithm, the same algorithm where orbital planes are simultaneously distributed on the sphere using a Fibonacci sequence
• Updated internal code in the model realization routines to use const values for algorithm constants rather than preprocessor values.

Comments

None of these changes affect existing EXP or pyEXP behavior. Perhaps addring might be dropped from this PR as too specific and idiosyncratic?

[michael-petersen]

All changes look good here -- but do we want to wait and do all IC updates simultaneously? Or we can merge this and start a new PR.

[The9Cat]

Maybe it's cleaner to add the gendisk quiet-start changes to this PR? The only advantage to merging now is the availability of the gensph quieter start. So do you want/need that any time soon? These things are rather specialized. E.g. the IC relaxation typically used for disk + halo will wipe out the quiet-start advantage.

[The9Cat]

This PR is going to get orphaned. I propose that I merge it with devel and close the PR.

[michael-petersen]

To make sure I understand: if the user does nothing, there will be no changes to the IC generation procedure (i.e. no 'quiet start'). Is that right?

I agree this should go in devel. It might make sense to open an issue with the enhancement for gendisk, since (at least for me) that's the reason this has remained open.

[The9Cat]

The problem with gendisk is: we almost always use some sort of IC relaxation. And that will wipe out any of the spatial arrangement that provides quiet-start benefit. So, not sure that this is worth the effort.

[The9Cat]

So, yes, I will open an Issue on gendisk and merge this branch to devel. Looks like I'll need to do this from the command line...

[The9Cat]

Sorry, forgot to answer the question: yes, the default behavior is the same as the original. There are new flags for quiet start: --Nrepl is the number of replicates of the orbit on the orbital plane, --Nfib is the number of orbital plane replicates spread on the sphere with a Fibonacci spiral.