dijkstra_fast (rubygems): Native implementation of Dijkstra algorithm for finding the shortest path between two vertices in a large, sparse graphs. Underlying algorithm is implemented in C using a priority queue.  Edges are represented using linked lists rather than an adjacency matrix to reduce memory footprint when operating on very large graphs where the average number of edges between nodes is relatively small (e.g. < 1/10 the number of nodes). See https://en.wikipedia.org/wiki/Dijkstra's_algorithm for additional information. 
Keywords: algorithm|dijkstra|native|ruby