Note that the MPID plugin used here carries along a full, anisotropic tensor representation of polarizability and a set of permanent multiples. Thus, we implement our simpler model zeroing the off-diagonal tensor elements and the permanent multipoles, but carrying along these more detailed terms necessarily slows the calculations. We are currently exploring how much further speedup can be attained with a more streamlined implementation. It is worth noting that the OpenMM implementation of iAMOEBA model achieved a speedup of simulations by a factor of 1.5 to 6 over full mutual polarization in the AMOEBA model, depending on the choices of convergence parameter in the SCF iterations. Therefore, we expect that greater speed of our direct polarization model will be achievable by further software engineering of the OpenMM polarizability plugin.