 This free energy map is also known as a "potential of mean force" or PMF.Free energy perturbation calculations only converge properly when the difference
between the two states is small enough; therefore it is usually necessary to divide a
perturbation into a series of smaller "windows", which are computed independently.Since there is no need for constant communication between the simulation for one
window and the next, the process can be trivially parallelized by running each window on
a different CPU, in what is known as an "embarrassingly parallel" setup.