Where simulation time t runs from [0, τ ], F (t) is a monodimensional FES obtained with data gathered up to time t, F (τ ) is the same quantity computed with all the data available. This quantity represents the average free energy difference per histogram bin in any of the D monodimensional free energy surfaces. Figure displays an example of δF M (t) computed for ϕ and ψ torsional angles of alanine dipeptide during concurrent metadynamics. The flattening of these differences as the fraction of utilized trajectory increases indicates that the simulation has been run for long enough that these torsions have been ergodically sampled.