[yt-users] HaloProfiler help

Britton Smith brittonsmith at gmail.com
Sat Mar 21 13:08:08 PDT 2009

Hi Stephen,

I have noticed this happening from time to time as well.  I have found that
you can often tell from looking at the radial profiles where the nan is
coming from.  I noticed just yesterday that I was getting some from halos
that had Overdensity profiles that were exactly flat for the two values
nearest to the critical overdensity, which are used for the interpolation to
calculate the virial quantities.  Many of these halos had max overdensities
that were less than the critical overdensity, and therefore, their virial
properties should be zeroes.  I made a couple updates in this regard to the
HaloProfiler just yesterday, so you may want to do an svn up.  Now, those
halos will be rejected from the virial quantities list intead of being
allowed in with nan values.

There may be other reasons the virial quantities are coming up nan.  If you
check out the radial profiles, it should be clear.  There may be something
that needs addressed that I didn't think of, so let us know if you find
anything strange.


On Sat, Mar 21, 2009 at 1:37 PM, Stephen Skory <stephenskory at yahoo.com>wrote:

> Hi,
> (this question refers to code in the trunk version of yt, not the 1.0
> version.)
> I am trying to calculate the virial mass for about 70,000 haloes in a
> fairly large cosmology simulation. Out of those, I'm only getting about
> 61,000 lines in VirialQuantities.out, and of those, 20,000 are actually
> nans. So out of 70,000 haloes from HOP, I have only about 40,000 virial
> masses.
> I don't imagine many people have run the HaloProfiler on a dataset this
> large, but is a 40% error rate typical? Can you suggest any strategies to
> minimize the number of nans and missing haloes? Is it likely I'm doing
> something wrong (which is a strong possibility)?
> Thanks!
>  _______________________________________________________
> sskory at physics.ucsd.edu           o__  Stephen Skory
> http://physics.ucsd.edu/~sskory/ <http://physics.ucsd.edu/%7Esskory/> _.>/
> _Graduate Student
> ________________________________(_)_\(_)_______________
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