Fast search algorithms for two metric characteristics problems on weighted graphs

Two problems are considered of metric characteristics search on weighted undirected graphs with non-negative edge weights. The first problem is to find the radius, diameter, at least one center, and one pair of peripheral vertices of an undirected graph with non-negative edge weights. In the second problem one also has the pre-calculated distances matrix. For these problems we propose fast search algorithms, which use only small fraction of graph vertices for metric characteristics search. The proposed algorithms are tested on various inputs against the other popular methods.