3.Algorithm analysisRecall known properties of relaxation-based algorithms: that have initialized by Initialization as above and changing values of d in calls to Relax only. If vertex v is reachable from s, we denote by opt(v) the (finite) cost of a shortest path from s to v in G , if a shortest path to v is well-defined, or , otherwise. We set opt(v) if v is not reachable from s. We say that opt(v) is the distance to v .Fact 3.1. Consider an arbitrary (properly initialized) sequence of Relax executions.