# Flat histogram¶

Flat histogram Monte Carlo methods bias the system along a macrostate, or order parameter, to observe uniform sampling and recover the free energy as a function of this order parameter.

FlatHistogram contains a Macrostate and a Bias. The Macrostate could be the number of particles or some other quantity such as the energy or a parameter of a model. The method of Bias includes Wang-Landau and Transition-Matrix. Importantly, the Bias computes the probability distribution of the macrostate on the fly, which is related to the free energy.

## Tools¶

For restarting multicore simulations, see /path/to/feasst/plugin/flat_histogram/tools/restart.cpp