Hi, I'm getting an error when trying to run MergerTree: amods.halo_merger_tree.MergerTree(restart_files=files, database='/home/molly-ucla/halos.db') It looks like it runs fine for the first two outputs and then stops: yt INFO 2010-12-16 09:59:59,440 Parameters: current_redshift = 85.4105867817 yt INFO 2010-12-16 09:59:59,440 Parameters: omega_lambda = 0.721 yt INFO 2010-12-16 09:59:59,440 Parameters: omega_matter = 0.279 yt INFO 2010-12-16 09:59:59,440 Parameters: hubble_constant = 0.701 Traceback (most recent call last): File "merger.py", line 10, in <module> amods.halo_merger_tree.MergerTree(restart_files=files, database='/home/molly-ucla/halos.db') File "/home/molly-ucla/yt-x86_64/lib/python2.6/site-packages/yt-2.0dev-py2.6-linux-x86_64.egg/yt/analysis_modules/halo_merger_tree/merger_tree.py", line 186, in __init__ self._run_halo_finder_add_to_db() File "/home/molly-ucla/yt-x86_64/lib/python2.6/site-packages/yt-2.0dev-py2.6-linux-x86_64.egg/yt/analysis_modules/halo_merger_tree/merger_tree.py", line 220, in _run_halo_finder_add_to_db if self.period == -1: ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() Nodes: tcc-2-0 Ideas? --Molly