private static List<String> shortestCycle(DirectedGraph<String, DefaultEdge> graph) {
FloydWarshallShortestPaths<String, DefaultEdge> floyd = new FloydWarshallShortestPaths<>(graph);
int minDistance = Integer.MAX_VALUE;
String minSource = null;
String minDestination = null;
for (DefaultEdge edge : graph.edgeSet()) {
String src = graph.getEdgeSource(edge);
String dst = graph.getEdgeTarget(edge);
int dist = (int) Math.round(floyd.shortestDistance(dst, src)); // from dst to src
if (dist < 0) {
continue;
}
if (dist < minDistance) {
minDistance = dist;
minSource = src;
minDestination = dst;
}
}
if (minSource == null) {
return null;
}
GraphPath<String, DefaultEdge> shortestPath = floyd.getShortestPath(minDestination, minSource);
List<String> pathVertexList = Graphs.getPathVertexList(shortestPath);
// note: pathVertexList will be [a, a] instead of [a] when the shortest path is a loop edge
if (!Objects.equals(shortestPath.getStartVertex(), shortestPath.getEndVertex())) {
pathVertexList.add(pathVertexList.get(0));
}
return pathVertexList;
}
public static void main(String[] args) {
TAP tap = TAP.BRAESS(TADriver.class);
List<String> odpairs = new ArrayList<>(tap.getOdpairs().keySet());
Collections.sort(odpairs);
String header = "average_tt";
String results = "";
// calculate all-shortest-path
FloydWarshallShortestPaths fws = new FloydWarshallShortestPaths(tap.getGraph());
// update the edges cost
for (String odPair : odpairs) {
String origin = odPair.split("-")[0];
String destination = odPair.split("-")[1];
GraphPath path = fws.getShortestPath(origin, destination);
for (Object e : path.getEdgeList()) {
StandardEdge edge = (StandardEdge) e;
edge.incrementTotalFlow(tap.getOdpairs().get(odPair).demandSize());
}
}
// evaluate cost per OD pair
for (String odPair : odpairs) {
header += Params.COLUMN_SEPARATOR + odPair;
String origin = odPair.split("-")[0];
String destination = odPair.split("-")[1];
results += Params.COLUMN_SEPARATOR + fws.getShortestPath(origin, destination).getWeight();
}
// print Result
List<AbstractEdge> edges = new ArrayList<>(tap.getGraph().edgeSet());
Collections.sort(edges);
double cost = 0.0;
for (AbstractEdge e : edges) {
header += Params.COLUMN_SEPARATOR + e.getName();
results += Params.COLUMN_SEPARATOR + e.getTotalFlow();
cost += (e.getCost() * e.getTotalFlow()) / tap.getDrivers().size();
}
System.out.println(header);
System.out.println(cost + results);
}