public void SimpleCycle()
{
var graph = new MutableDirectedGraph();
NodeId a = graph.CreateNode();
NodeId b = graph.CreateNode();
NodeId c = graph.CreateNode();
NodeId d = graph.CreateNode();
NodeId e = graph.CreateNode();
NodeId f = graph.CreateNode();
graph.AddEdge(a, b);
graph.AddEdge(b, c);
graph.AddEdge(c, b); // Cycle-forming backedge (violates topo order).
graph.AddEdge(d, e);
graph.AddEdge(e, f);
XAssert.IsTrue(graph.IsReachableFrom(a, b), "Shouldn't visit the backedge");
XAssert.IsTrue(graph.IsReachableFrom(a, c), "Shouldn't visit the backedge");
try
{
// Note that to fail, we need a > e here due to a fast-path for 'unreachable'
// that doesn't look at any edges.
graph.IsReachableFrom(a, f); // Fails since it should find the backedge c -> b
}
catch (BuildXLException)
{
return;
}
XAssert.Fail("Expected a failure due to a topological order violation");
}
public void DisconnectedNodes()
{
var graph = new MutableDirectedGraph();
NodeId a = graph.CreateNode();
NodeId b = graph.CreateNode();
XAssert.IsFalse(graph.IsReachableFrom(a, b));
XAssert.IsFalse(graph.IsReachableFrom(b, a));
}
public void TriviallyConnectedNodes()
{
var graph = new MutableDirectedGraph();
NodeId a = graph.CreateNode();
NodeId b = graph.CreateNode();
graph.AddEdge(a, b);
XAssert.IsTrue(graph.IsReachableFrom(a, b));
XAssert.IsFalse(graph.IsReachableFrom(b, a));
}
public void TopologicalOrderViolationsIgnoredIfRequested()
{
var graph = new MutableDirectedGraph();
NodeId a = graph.CreateNode();
NodeId b = graph.CreateNode();
NodeId c = graph.CreateNode();
NodeId d = graph.CreateNode();
graph.AddEdge(a, b);
graph.AddEdge(d, c); // This edge breaks the topological labelling.
XAssert.IsFalse(graph.IsReachableFrom(a, c, skipOutOfOrderNodes: true));
}
public void MultipleLevels()
{
var graph = new MutableDirectedGraph();
NodeId l0 = graph.CreateNode();
NodeId l1_n1 = graph.CreateNode();
NodeId l1_n2 = graph.CreateNode();
graph.AddEdge(l0, l1_n1);
graph.AddEdge(l0, l1_n2);
graph.AddEdge(l1_n1, l1_n2);
NodeId l2_n1 = graph.CreateNode();
NodeId l2_n2 = graph.CreateNode();
graph.AddEdge(l1_n1, l2_n1);
graph.AddEdge(l1_n2, l2_n2);
NodeId l3_n1 = graph.CreateNode();
NodeId l3_n2 = graph.CreateNode();
graph.AddEdge(l2_n1, l3_n1);
graph.AddEdge(l2_n2, l3_n2);
NodeId l4 = graph.CreateNode();
graph.AddEdge(l3_n1, l4);
graph.AddEdge(l3_n2, l4);
XAssert.IsTrue(graph.IsReachableFrom(l1_n1, l3_n2));
XAssert.IsTrue(graph.IsReachableFrom(l0, l4));
XAssert.IsFalse(graph.IsReachableFrom(l3_n2, l1_n1));
XAssert.IsFalse(graph.IsReachableFrom(l4, l0));
}
public void TrivialViolationOfTopologicalOrder()
{
var graph = new MutableDirectedGraph();
NodeId a = graph.CreateNode();
NodeId b = graph.CreateNode();
NodeId c = graph.CreateNode();
NodeId d = graph.CreateNode();
graph.AddEdge(a, b);
graph.AddEdge(d, c); // This edge breaks the topological labelling.
try
{
// Note that to fail, we need c > a here due to a fast-path for 'unreachable'
// that doesn't look at any edges.
graph.IsReachableFrom(a, c);
}
catch (BuildXLException)
{
return;
}
XAssert.Fail("Expected a failure due to a topological order violation");
}
