The limitation of force constants results in a narrower range of feasible solutions for the optimal parameters. In Swarm-CG, the match between coarse-grained and atomistic distributions is evaluated via the so-called Earth Mover's distance (EMD) . The similarity of the distributions can serve as an indicator of how accurately the coarse-grained model reproduces the dynamics of the grouped (mapped) atoms. In other words, a closer alignment between the two distributions corresponds to a smaller EMD value (for details about the EMD, please refer to Section S5 in the Supporting Information).