Version 1.0b2.dev0 seems slower than 1.0b1.dev0

[Qcellaris]

I have installed the latest version of PySPH (1.0b2.dev0) in a new virtual environment. On the same machine I already had 1.0b1.dev0 installed in an older virtual environment. Now when I run the exact same simulation in both environments it turns out that the 1.0b2.dev0 version is about 10% slower. I didn't recognize this difference on short runs but on longer simulations it becomes more clear. Any idea how this is possible?