New issue 697: when halo merger tree fails because it runs out of viable halos to track, give an appropriate error message https://bitbucket.org/yt_analysis/yt/issue/697/when-halo-merger-tree-fails-b... Cameron Hummels: right now, when the halo merger tree runs out of halos as it tracks back in time (usually in the z>20 regime), it gives a generic error: ========== Cycle 00006 (z=29.999961) ========== Traceback (most recent call last): File "enzo.py", line 33, in <module> mt.save_halo_evolution('halos.h5') 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 It would be nice to have this give an error saying what actually happened--it ran out of halos!