@Test
public void testFlagFeedbackEdgesOnSimpleLoop() {
DirectedGraph<String, StringEdge> dcg = DirectedGraph.createStringDirectedGraph();
dcg.addEdge("A", "B", 3).addEdge("B", "A", 1);
CycleDetector<String> cycleDetector = new CycleDetector<String>(dcg);
cycleDetector.detectCycles();
MinimumFeedbackEdgeSetSolver solver =
new MinimumFeedbackEdgeSetSolver(cycleDetector.getCycles());
Set<Edge> feedbackEdges = solver.getEdges();
assertTrue(feedbackEdges.contains(dcg.getEdge("B", "A")));
}
@Test
public void testGetFeedbackEdgesOnComplexGraph() {
DirectedGraph<String, StringEdge> dcg = DirectedGraph.createStringDirectedGraph();
dcg.addEdge("A", "B", 7).addEdge("B", "C", 3).addEdge("C", "D", 1).addEdge("D", "A", 3);
dcg.addEdge("B", "A", 12);
CycleDetector<String> cycleDetector = new CycleDetector<String>(dcg);
cycleDetector.detectCycles();
MinimumFeedbackEdgeSetSolver solver =
new MinimumFeedbackEdgeSetSolver(cycleDetector.getCycles());
Set<Edge> feedbackEdges = solver.getEdges();
assertThat(feedbackEdges.size(), is(1));
assertTrue(feedbackEdges.contains(dcg.getEdge("A", "B")));
}
@Test
public void testApproximateMinimumFeedbackEdges() {
DirectedGraph<String, StringEdge> dcg = DirectedGraph.createStringDirectedGraph();
dcg.addEdge("A", "B", 5).addEdge("B", "C", 9).addEdge("C", "A", 1);
dcg.addEdge("D", "B", 5).addEdge("C", "D", 7);
dcg.addEdge("F", "B", 5).addEdge("C", "F", 4);
CycleDetector<String> cycleDetector = new CycleDetector<String>(dcg);
cycleDetector.detectCycles();
MinimumFeedbackEdgeSetSolver minimumSolver =
new MinimumFeedbackEdgeSetSolver(cycleDetector.getCycles());
assertThat(minimumSolver.getEdges().size(), is(1));
assertTrue(minimumSolver.getEdges().contains(dcg.getEdge("B", "C")));
MinimumFeedbackEdgeSetSolver approximateSolver =
new MinimumFeedbackEdgeSetSolver(cycleDetector.getCycles(), 2);
assertThat(approximateSolver.getEdges().size(), is(2));
assertTrue(approximateSolver.getEdges().contains(dcg.getEdge("B", "C")));
assertTrue(approximateSolver.getEdges().contains(dcg.getEdge("C", "A")));
}
@Test
public void testFlagFeedbackEdgesOnUnrelatedCycles() {
DirectedGraph<String, StringEdge> dcg = DirectedGraph.createStringDirectedGraph();
dcg.addEdge("A", "B", 7).addEdge("B", "C", 3).addEdge("C", "A", 2);
dcg.addEdge("D", "E", 3).addEdge("E", "D", 5);
dcg.addEdge("F", "G", 1).addEdge("G", "H", 4).addEdge("H", "F", 7);
CycleDetector<String> cycleDetector = new CycleDetector<String>(dcg);
cycleDetector.detectCycles();
MinimumFeedbackEdgeSetSolver solver =
new MinimumFeedbackEdgeSetSolver(cycleDetector.getCycles());
Set<Edge> feedbackEdges = solver.getEdges();
assertThat(feedbackEdges.size(), is(3));
assertTrue(feedbackEdges.contains(dcg.getEdge("C", "A")));
assertTrue(feedbackEdges.contains(dcg.getEdge("D", "E")));
assertTrue(feedbackEdges.contains(dcg.getEdge("F", "G")));
}