Test performance impact of masses in VelocityVerlet and Langevin
The handling of masses in VelocityVerlet has changed. Check impact of this, in particular it may be better to use per-atom masses instead of per-Z masses.
Also, in Langevin there is a possibility that two copies of the masses are copied around in parallel simulations, one for the atoms and one for the dynamics. This may also affect other kinds of dynamics, check this.