Hi all, If you've been using unitrefactor, updating to the latest version should come with a big performance boost for nearly all yt operations. More details here: https://bitbucket.org/MatthewTurk/yt/pull-request/67/refactor-the-unit-syste... To update: $ hg pull -r yt-3.0 https://bitbucket.org/MatthewTurk/yt $ hg up $ python setup.py develop Be sure to save any uncommitted changes with hg shelve first. -Nathan