Stephen Skory has added the Friends-of-friends halo finder to the yt trunk (not yt-1.0) and we've now enabled it as a possibility for finding halos in a simulation. Because there are now two mechanisms for finding halos, we've also changed the API a little bit and made the halo finders available through yt.mods. So to run the HOP halo finder you would do the following:
from yt.mods import * pf = load("data0001") halo_list = HaloFinder(pf)
and to run FOF you have to call it slightly differently:
from yt.mods import * pf = load("data0001") halo_list = FOFHaloFinder(pf)
To get FOF to compile, you'll have to rerun "python setup.py develop" or "python setup.py install" depending on how yt was installed initially. (The install_script does the former, but most hand-installs do the latter.) With this new API, both halo finders run in parallel. I'll save any discussion of that for Stephen, however, as there are some caveats to running HOP in parallel. Additionally, as of right now they dont scale as well as we'd like -- but we're working on it.
Additionally, as a result of this change we have intentionally broken compatibility by removing the import of the 'hop' module in yt/mods.py. Hopefully this has not caused too many problems; all of the old, largely duplicated-in-multiple-places classes and interfaces have now been consolidated and placed in yt/lagos/HaloFinding.py.
Thanks to Stephen for his hard work adding in FOF and working with the parallel interface!
Best wishes, and let us know if there are any problems,