Wang-Landau Density of States

The Wang-Landau algorithm is a flat-histogram Monte Carlo method that estimates the density of states g(E) of a statistical system in a single random walk — replacing separate Metropolis simulations at every temperature with one run whose output gives the full thermodynamics of the system at any temperature by direct summation. This simulator runs the algorithm live on a 2D Ising spin lattice: a 3D grid of red/blue spins shows the current microstate while an adjoining bar chart builds up ln g(E) in real time, the modification factor ln f halving each time the visit histogram becomes flat enough, exactly as in the original 2001 Wang-Landau paper.