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");
}
/// <summary>
/// Creates a test graph.
/// There are light edges between nodes 0 - 1, 1 - 2, and 2 - 0.
/// There are heavy edges between 0 - 1 and 1 - 3
/// </summary>
private static void CreateGraphWithLightEdges(out MutableDirectedGraph graph, out NodeId[] nodes)
{
graph = new MutableDirectedGraph();
XAssert.AreEqual(graph.NodeCount, 0);
XAssert.AreEqual(graph.EdgeCount, 0);
// Test creation.
nodes = new NodeId[4];
for (int i = 0; i < nodes.Length; ++i)
{
nodes[i] = graph.CreateNode();
}
XAssert.AreEqual(graph.NodeCount, nodes.Length);
XAssert.AreEqual(graph.EdgeCount, 0);
foreach (NodeId t in nodes)
{
XAssert.IsTrue(graph.ContainsNode(t));
XAssert.IsTrue(graph.IsSourceNode(t));
XAssert.IsTrue(graph.IsSinkNode(t));
}
graph.AddEdge(nodes[0], nodes[1], isLight: true);
graph.AddEdge(nodes[1], nodes[2], isLight: true);
graph.AddEdge(nodes[2], nodes[0], isLight: true);
graph.AddEdge(nodes[0], nodes[1], isLight: false);
graph.AddEdge(nodes[1], nodes[3], isLight: false);
}
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 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 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");
}
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));
}
private static IReadonlyDirectedGraph CreateRandomAcyclicGraph(Random rng, int nodeCount)
{
var graph = new MutableDirectedGraph();
var nodes = new NodeId[nodeCount];
for (int i = 0; i < nodeCount; i++)
{
nodes[i] = graph.CreateNode();
}
for (int i = 0; i < nodeCount; i++)
{
int toIndex = i;
while ((toIndex = rng.Next(toIndex + 1, nodeCount)) < nodeCount)
{
graph.AddEdge(nodes[i], nodes[toIndex]);
}
}
return(graph);
}
/// <summary>
/// Creates a test graph.
/// </summary>
private static void CreateGraph(out MutableDirectedGraph graph, out NodeId[] nodes)
{
graph = new MutableDirectedGraph();
XAssert.AreEqual(graph.NodeCount, 0);
XAssert.AreEqual(graph.EdgeCount, 0);
// Test creation.
nodes = new NodeId[12];
for (int i = 0; i < nodes.Length; ++i)
{
nodes[i] = graph.CreateNode();
}
XAssert.AreEqual(graph.NodeCount, nodes.Length);
XAssert.AreEqual(graph.EdgeCount, 0);
foreach (NodeId t in nodes)
{
XAssert.IsTrue(graph.ContainsNode(t));
XAssert.IsTrue(graph.IsSourceNode(t));
XAssert.IsTrue(graph.IsSinkNode(t));
}
graph.AddEdge(nodes[5], nodes[0]);
graph.AddEdge(nodes[5], nodes[1]);
graph.AddEdge(nodes[6], nodes[1]);
graph.AddEdge(nodes[6], nodes[2]);
graph.AddEdge(nodes[7], nodes[5]);
graph.AddEdge(nodes[8], nodes[5]);
graph.AddEdge(nodes[9], nodes[6]);
graph.AddEdge(nodes[9], nodes[3]);
graph.AddEdge(nodes[9], nodes[4]);
graph.AddEdge(nodes[10], nodes[8]);
graph.AddEdge(nodes[11], nodes[8]);
graph.AddEdge(nodes[11], nodes[9]);
}
