internal override void CheckInvariant(ILPhase phase)
{
base.CheckInvariant(phase);
int firstArgument = (OpCode != OpCode.NewObj && !Method.IsStatic) ? 1 : 0;
Debug.Assert(Method.Parameters.Count + firstArgument == Arguments.Count);
Debug.Assert(Method.Parameters.Count + firstArgument == ArgumentToParameterMap.Length);
if (firstArgument == 1)
{
Debug.Assert(Arguments[0].ResultType == ExpectedTypeForThisPointer(ConstrainedTo ?? Method.DeclaringType),
$"Stack type mismatch in 'this' argument in call to {Method.Name}()");
Debug.Assert(ArgumentToParameterMap[0] == -1, "'this' argument must always be mapped at position 0");
}
int paramCount = Method.Parameters.Count;
if (paramCount > 0)
{
BitSet bitSet = new BitSet(paramCount);
for (int i = 0; i < paramCount; ++i)
{
int mappedTo = ArgumentToParameterMap[firstArgument + i];
Debug.Assert(mappedTo >= 0 && mappedTo < paramCount, $"mapping out of [0..{paramCount}[, was: {mappedTo}");
Debug.Assert(!bitSet[mappedTo], $"argument {mappedTo} is already mapped to a different parameter");
bitSet.Set(mappedTo);
Debug.Assert(Arguments[firstArgument + i].ResultType == Method.Parameters[mappedTo].Type.GetStackType(),
$"Stack type mismatch in parameter {mappedTo} (argument {firstArgument + i}) in call to {Method.Name}()");
}
Debug.Assert(bitSet.All(0, paramCount - 1), "Not all arguments are mapped to a parameter");
}
}
public void AllInRange()
{
var bitset = new BitSet(300);
bitset.Set(1, 299);
Assert.IsTrue(bitset.All(1, 299));
Assert.IsTrue(bitset.All(10, 290));
Assert.IsTrue(bitset.All(100, 200));
Assert.IsFalse(bitset.All(0, 200));
Assert.IsFalse(bitset.All(0, 1));
Assert.IsFalse(bitset.All(1, 300));
bitset[200] = false;
Assert.IsFalse(bitset.All(1, 299));
}
/// <summary>
/// Tests if the graph can be separated with a safe separator of size 2. If so, the separator is saved in the "separator" member variable
/// </summary>
/// <returns>true iff a size 2 separator exists</returns>
public bool FindSize2Separator()
{
BitSet notIgnoredVertices = BitSet.All(graph.vertexCount);
// loop over every pair of vertices
for (int u = 0; u < graph.vertexCount; u++)
{
notIgnoredVertices[u] = false;
foreach (int a in ArticulationPoints(graph, notIgnoredVertices))
{
separator = new BitSet(graph.vertexCount);
separator[u] = true;
separator[a] = true;
separatorType = SeparatorType.Size2;
return(true);
}
notIgnoredVertices[u] = true;
}
return(false);
}
/// <summary>
/// lists all articulation points of the graph
/// This method can also be used to test for separators of size n by passing a set of n-1 vertices as
/// ignoredVertices. and combining the result with the ignoredVertices.
/// Code adapated from https://slideplayer.com/slide/12811727/
/// </summary>
/// <param name="availableVertices">a list of vertices to treat as existent</param>
/// <returns>an iterator over all articulation points</returns>
public static IEnumerable <int> ArticulationPoints(Graph graph, BitSet availableVertices = null)
{
if (graph.vertexCount == 0) // exit early if there are no vertices
{
yield break;
}
availableVertices = availableVertices ?? BitSet.All(graph.vertexCount); // create an empty list if the given one is null in order to prevent NullReferenceExceptions
int start = availableVertices.First();
int[] count = new int[graph.vertexCount]; // TODO: make member variable
int[] reachBack = new int[graph.vertexCount]; // TODO: make member variable
Queue <int>[] children = new Queue <int> [graph.vertexCount]; // TODO: make member variable
for (int i = 0; i < graph.vertexCount; i++)
{
count[i] = int.MaxValue;
reachBack[i] = int.MaxValue;
children[i] = new Queue <int>();
}
count[start] = 0;
int numSubtrees = 0;
for (int i = 0; i < graph.adjacencyList[start].Count; i++)
{
int rootNeighbor = graph.adjacencyList[start][i];
if (count[rootNeighbor] == int.MaxValue && availableVertices[rootNeighbor])
{
Stack <(int, int, int)> stack = new Stack <(int, int, int)>();
stack.Push((rootNeighbor, 1, start));
while (stack.Count > 0)
{
(int node, int timer, int fromNode) = stack.Peek();
if (count[node] == int.MaxValue)
{
count[node] = timer;
reachBack[node] = timer;
List <int> neighbors = graph.adjacencyList[node];
for (int j = 0; j < neighbors.Count; j++)
{
int neighbor = neighbors[j];
if (neighbor != fromNode && availableVertices[neighbor])
{
children[node].Enqueue(neighbor);
}
}
}
else if (children[node].Count > 0)
{
int child = children[node].Dequeue();
if (count[child] < int.MaxValue)
{
if (reachBack[node] > count[child])
{
reachBack[node] = count[child];
}
}
else
{
stack.Push((child, timer + 1, node));
}
}
else
{
if (node != rootNeighbor)
{
if (reachBack[node] >= count[fromNode])
{
yield return(fromNode);
}
if (reachBack[fromNode] > reachBack[node])
{
reachBack[fromNode] = reachBack[node];
}
}
stack.Pop();
}
}
numSubtrees++;
}
}
if (numSubtrees > 1)
{
yield return(start);
}
}
/// <summary>
/// finds candidate safe separators using a heuristic. This is Tamaki's code.
/// </summary>
/// <param name="mode"></param>
/// <returns></returns>
public static List <BitSet> Tamaki_HeuristicVerticesAndNeighbors(Graph graph, Heuristic mode)
{
// code adapted from https://github.com/TCS-Meiji/PACE2017-TrackA/blob/master/tw/exact/GreedyDecomposer.java
List <BitSet> separators = new List <BitSet>();
// ----- lines 62 to 64 -----
// copy fields so that we can change them locally
Graph copy = new Graph(graph);
List <BitSet> frontier = new List <BitSet>();
BitSet remaining = BitSet.All(graph.vertexCount);
// ----- lines 66 to 80 -----
while (!remaining.IsEmpty())
{
// ----- lines 67 to 80 -----
int vmin = FindMinCostVertex(remaining, copy, mode);
// ----- line 82 -----
List <BitSet> joined = new List <BitSet>();
// lines 84 and 85 -----
BitSet toBeAclique = new BitSet(graph.vertexCount);
toBeAclique[vmin] = true;
// ----- lines 87 to 93 -----
foreach (BitSet s in frontier)
{
if (s[vmin])
{
joined.Add(s);
toBeAclique.UnionWith(s);
}
}
// ----- lines 97 to 119 -----
if (joined.Count == 0)
{
toBeAclique[vmin] = true;
}
else if (joined.Count == 1)
{
BitSet uniqueSeparator = joined[0];
BitSet test = new BitSet(copy.openNeighborhood[vmin]);
test.IntersectWith(remaining);
if (uniqueSeparator.IsSupersetOf(test))
{
uniqueSeparator[vmin] = false;
if (uniqueSeparator.IsEmpty())
{
separators.Remove(uniqueSeparator);
frontier.Remove(uniqueSeparator);
}
remaining[vmin] = false;
continue;
}
}
// ----- line 121 -----
BitSet temp = new BitSet(copy.openNeighborhood[vmin]);
temp.IntersectWith(remaining);
toBeAclique.UnionWith(temp);
// ----- line 129 -----
copy.MakeIntoClique(toBeAclique.Elements());
// ----- lines 131 and 132 -----
BitSet sep = new BitSet(toBeAclique);
sep[vmin] = false;
// ----- lines 134 to 147 -----
if (!sep.IsEmpty())
{
BitSet separator = new BitSet(sep);
separators.Add(separator);
frontier.Add(separator);
}
// ----- lines 153 to 161 -----
foreach (BitSet s in joined)
{
Debug.Assert(!s.IsEmpty());
frontier.Remove(s);
}
remaining[vmin] = false;
}
return(separators);
}
