Hi Cameron,
Thanks, You are very right.  Indeed, the problem was coming from the fact that it could not parent halo at higher redshift (i.e., z= 40). It was misleading to some other error which confused me.  It might be good to put a check statement in the code that halofinder is unable to find parents or some thing similar.

On Tue, Oct 29, 2013 at 2:19 PM, Cameron Hummels <chummels@gmail.com> wrote:
Hi Latif,

Thanks for the detailed information including the yt version and the output!

What you're experiencing here looks like normal behavior actually, at least in my experience.  When the merger tree tracks halos back in time, it goes from timestep output to earlier timestep output, looking for the halo at a previous timestep which contains the largest number of the particles in the current timestep.  Unfortunately, at early times, like z=30, very few halos have actually formed because they just haven't had enough time for gravitational collapse to take over.  Thus, the merger tree fails because it cannot find a parent halo at that timestep.

However, it might be worthwhile for us to make the error message more explanatory so that it's obvious what is happening.  I'll make an issue for this to be corrected in the future.


On Tue, Oct 29, 2013 at 4:12 AM, Latif <latifne@gmail.com> wrote:
Hi all,
I am running merger tree on Enzo simulations following the recipe given in YT documentation. YT crashes by producing the following error. I am using yt version "b118390aa42c".  Any ideas what is going on here?

FOF CPU TIME: 2.408634 secs
========== Cycle 00009 (z=9.999997) ==========
Parent halo = 0
--> Most massive progenitor == Halo -1
========== Cycle 00008 (z=14.999989) ==========
========== Cycle 00007 (z=19.999992) ==========
========== Cycle 00006 (z=29.999961) ==========
Traceback (most recent call last):
  File "enzo.py", line 33, in <module>
  File "/home/uni05/mlatif/ytnew/yt-x86_64/src/yt-hg/yt/analysis_modules/halo_merger_tree/enzofof_merger_tree.py", line 507, in save_halo_evolution
    halo_id = self.levels[cycle_fin][0].halo_id
IndexError: list index out of range

Thanks in advance,

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Cameron Hummels
Postdoctoral Researcher
Steward Observatory
University of Arizona

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