public void TarjanStronglyConnected_Smoke_Test()
{
var graph = new DiGraph <char>();
graph.AddVertex('A');
graph.AddVertex('B');
graph.AddVertex('C');
graph.AddVertex('D');
graph.AddVertex('E');
graph.AddVertex('F');
graph.AddVertex('G');
graph.AddVertex('H');
graph.AddEdge('A', 'B');
graph.AddEdge('B', 'C');
graph.AddEdge('C', 'A');
graph.AddEdge('C', 'D');
graph.AddEdge('D', 'E');
graph.AddEdge('E', 'F');
graph.AddEdge('F', 'G');
graph.AddEdge('G', 'E');
graph.AddEdge('F', 'H');
var algorithm = new TarjansStronglyConnected <char>();
var result = algorithm.FindStronglyConnectedComponents(graph);
Assert.AreEqual(4, result.Count);
var expectedResult = new List <List <char> >()
{
new char[] { 'H' }.ToList(),
new char[] { 'E', 'F', 'G' }.ToList(),
new char[] { 'D' }.ToList(),
new char[] { 'A', 'B', 'C' }.ToList()
};
for (int i = 0; i < expectedResult.Count; i++)
{
var expectation = expectedResult[i];
var actual = result[i];
Assert.IsTrue(expectation.Count == actual.Count);
foreach (var vertex in expectation)
{
Assert.IsTrue(actual.Contains(vertex));
}
}
}
/// <summary>
/// Breaks cycles in the graph, returning all edges that changed their orientation.
/// </summary>
/// <param name="graph"></param>
/// <returns></returns>
public List <(Operation Operation1, Operation Operation2)> BreakCycles(DiGraph <Operation> graph)
{
var changedOrientationEdges = new List <(Operation Operation1, Operation Operation2)>();
var algorithm = new TarjansStronglyConnected <Operation>();
List <List <Operation> > components;
do
{
// find strongly connected components
components = algorithm.FindStronglyConnectedComponents(graph).Where(x => x.Count > 1).ToList();
foreach (List <Operation> component in components.AsShuffledEnumerable())
{
var componentHashSet = component.ToHashSet();
foreach (var operation1 in component.AsShuffledEnumerable())
{
// get all neighbor operations that are in the same component
var neighborOperations = GetNeighborComponentOperations(graph, operation1, componentHashSet);
foreach (var operation2 in neighborOperations.AsShuffledEnumerable())
{
// two operations are not on the same job
// but are on the same machines (=> can switch their edge orientation if I need to)
if (operation1.JobId != operation2.JobId &&
operation1.MachineId == operation2.MachineId)
{
double probability = RandomizationProvider.Current.GetDouble();
// switch directions of edge with prob for back edge, forward edge or same level edge
if ((operation1.Order > operation2.Order && probability <= backEdgeBreakProbability) ||
(operation1.Order < operation2.Order && probability <= forwardEdgeBreakProbability) ||
(operation1.Order == operation2.Order && probability <= sameLevelEdgeBreakProbability))
{
// switch edge orientation
graph.RemoveEdge(operation1, operation2);
graph.AddEdge(operation2, operation1);
changedOrientationEdges.Add((operation1, operation2));
goto cycleOut;
}
}
}
}
}
cycleOut :;
} while (components.Count > 0);
return(changedOrientationEdges);
}
