Options: - [x] Extrapolation via static PDE ([ref](https://www.math.uci.edu/~zhao/homepage/Publication_files/SISCR3.pdf)) such as extrap_LS in examples/PeriodicSoftSlab. Might apply `extend_velocities` function in [skfmm](https://pythonhosted.org/scikit-fmm/). - [ ] speedup the above method - [ ] Implement least square extrapolation in python ([ref](https://www.sciencedirect.com/science/article/pii/S0021999119306278)).
Options:
extend_velocitiesfunction in skfmm.