Path Sum I I Algorithm

Another advantage is that it is in practice easier to guess the correct form of the Lagrangian of a theory, which naturally enters the path integrals (for interactions of a certain type, these are coordinate space or Feynman path integrals), than the Hamiltonian. The path integral formulation is a description in quantum mechanics that generalizes the action principle of classical mechanics.

Path Sum I I source code, pseudocode and analysis