saturation vector is of same size as velocity. Therefore, we need to use
a mapping from configuration indices to velocity indices.
A constructor taking such an object has been added. For backward
compatibility, the default constructor builds a trivial mapping.
saturation vector is of same size as velocity. Therefore, we need to use a mapping from configuration indices to velocity indices. A constructor taking such an object has been added. For backward compatibility, the default constructor builds a trivial mapping.