/// <summary>Contrived example to test blossoming.</summary>
[TestMethod()] public void Blossom()
{
Graph g = Graph.FromSmiles("CCCCCC1CCCC1CC");
Matching m = Matching.CreateEmpty(g);
// initial matching from double-bonds (size = 5)
m.Match(1, 2);
m.Match(3, 4);
m.Match(5, 6);
m.Match(7, 8);
m.Match(9, 10);
MaximumMatching.Maximise(g, m, 10);
// once maximised the matching has been augmented such that there
// are now six disjoint edges (only possibly by contracting blossom)
Assert.AreEqual(6, m.GetMatches().Count());
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] {
Tuple.Of(0, 1),
Tuple.Of(2, 3),
Tuple.Of(4, 5),
Tuple.Of(6, 7),
Tuple.Of(8, 9),
Tuple.Of(10, 11),
},
m.GetMatches()));
}
/// <summary>
/// An edge was found which connects two 'even' vertices in the forest. If
/// the vertices have the same root we have a blossom otherwise we have
/// identified an augmenting path. This method checks for these cases and
/// responds accordingly.
/// <para>
/// If an augmenting path was found - then it's edges are alternated and the
/// method returns true. Otherwise if a blossom was found - it is contracted
/// and the search continues.
/// </para>
/// </summary>
/// <param name="v">endpoint of an edge</param>
/// <param name="w">another endpoint of an edge</param>
/// <returns>a path was augmented</returns>
private bool Check(int v, int w)
{
// self-loop (within blossom) ignored
if (uf.Connected(v, w))
{
return(false);
}
vAncestors.SetAll(false);
wAncestors.SetAll(false);
int vCurr = v;
int wCurr = w;
// walk back along the trees filling up 'vAncestors' and 'wAncestors'
// with the vertices in the tree - vCurr and wCurr are the 'even' parents
// from v/w along the tree
while (true)
{
vCurr = Parent(vAncestors, vCurr);
wCurr = Parent(wAncestors, wCurr);
// v and w lead to the same root - we have found a blossom. We
// travelled all the way down the tree thus vCurr (and wCurr) are
// the base of the blossom
if (vCurr == wCurr)
{
Blossom(v, w, vCurr);
return(false);
}
// we are at the root of each tree and the roots are different, we
// have found and augmenting path
if (uf.Find(even[vCurr]) == vCurr && uf.Find(even[wCurr]) == wCurr)
{
Augment(v);
Augment(w);
matching.Match(v, w);
return(true);
}
// the current vertex in 'v' can be found in w's ancestors they must
// share a root - we have found a blossom whose base is 'vCurr'
if (wAncestors[vCurr])
{
Blossom(v, w, vCurr);
return(false);
}
// the current vertex in 'w' can be found in v's ancestors they must
// share a root, we have found a blossom whose base is 'wCurr'
if (vAncestors[wCurr])
{
Blossom(v, w, wCurr);
return(false);
}
}
}
public void Adjusted_other_invalid()
{
Matching matching = Matching.CreateEmpty(Graph.FromSmiles("CCCCC"));
matching.Match(0, 1);
matching.Match(2, 3);
matching.Match(1, 2); // 0-1 and 2-3 should not be
matching.Other(0);
}
[TestMethod()] public void Adjusted_other()
{
Matching matching = Matching.CreateEmpty(Graph.FromSmiles("CCCCC"));
matching.Match(0, 1);
matching.Match(2, 3);
matching.Match(1, 2); // 0-1 and 2-3 should not be
Assert.AreEqual(matching.Other(1), 2);
Assert.AreEqual(matching.Other(2), 1);
}
[TestMethod()] public void Basic()
{
Matching matching = Matching.CreateEmpty(Graph.FromSmiles("CCCCC"));
matching.Match(0, 1);
matching.Match(2, 3);
Assert.AreEqual(2, matching.GetMatches().Count());
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] { Tuple.Of(0, 1), Tuple.Of(2, 3) },
matching.GetMatches()));
}
[TestMethod()] public void Adjusted_contains()
{
Matching matching = Matching.CreateEmpty(Graph.FromSmiles("CCCCC"));
matching.Match(0, 1);
matching.Match(2, 3);
matching.Match(1, 2); // 0-1 and 2-3 should not be
Assert.IsFalse(matching.Unmatched(1));
Assert.IsFalse(matching.Unmatched(2));
Assert.IsTrue(matching.Unmatched(0));
Assert.IsTrue(matching.Unmatched(3));
}
public void Adjusted()
{
Matching matching = Matching.CreateEmpty(Graph.FromSmiles("CCCCC"));
matching.Match(0, 1);
matching.Match(2, 3);
matching.Match(1, 2); // 0-1 and 2-3 should not be
Assert.IsFalse(Compares.AreOrderLessDeepEqual(
new[] { Tuple.Of(0, 1), Tuple.Of(2, 3) },
matching.GetMatches()));
Assert.AreEqual(1, matching.GetMatches().Count());
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] { Tuple.Of(1, 2) },
matching.GetMatches()));
}
/// <summary>
/// Create an arbitrary matching on the subset of vertices ('s') of provided
/// graph. The provided matching should be empty.
///
/// <param name="g">graph to match</param>
/// <param name="m">empty matching (presumed)</param>
/// <param name="s">subset of vertices</param>
/// <returns>number of vertices matched</returns>
/// </summary>
public static int Initial(Graph g, Matching m, BitArray s)
{
int nMatched = 0;
for (int v = BitArrays.NextSetBit(s, 0); v >= 0; v = BitArrays.NextSetBit(s, v + 1))
{
// skip if already matched
if (m.Matched(v))
{
continue;
}
// find a single edge which is not matched and match it
int d = g.Degree(v);
for (int j = 0; j < d; ++j)
{
Edge e = g.EdgeAt(v, j);
int w = e.Other(v);
if ((e.Bond != Bond.Single) && m.Unmatched(w) && s[w])
{
m.Match(v, w);
nMatched += 2;
break;
}
}
}
return(nMatched);
}
[TestMethod()] public void Simple_augment()
{
Graph g = Graph.FromSmiles("cccc");
Matching m = Matching.CreateEmpty(g);
m.Match(1, 2);
MaximumMatching.Maximise(g, m, 2);
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] { Tuple.Of(0, 1), Tuple.Of(2, 3) },
m.GetMatches()));
}
public void Napthalene_augment()
{
Graph g = Graph.FromSmiles("C1C=CC2=CCC=CC2=C1");
Matching m = Matching.CreateEmpty(g);
m.Match(1, 2);
m.Match(3, 4);
m.Match(6, 7);
m.Match(8, 9);
MaximumMatching.Maximise(g, m, 8);
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] {
Tuple.Of(0, 1),
Tuple.Of(2, 3),
Tuple.Of(4, 5),
Tuple.Of(6, 7),
Tuple.Of(8, 9),
},
m.GetMatches()));
}
[TestMethod()] public void Furan_augment()
{
Graph g = Graph.FromSmiles("o1cccc1");
IntSet s = IntSet.AllOf(1, 2, 3, 4); // exclude the oxygen
Matching m = Matching.CreateEmpty(g);
m.Match(2, 3);
MaximumMatching.Maximise(g, m, 2, s);
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] { Tuple.Of(1, 2), Tuple.Of(3, 4) },
m.GetMatches()));
}
[TestMethod()] public void Simple_augment_subset()
{
Graph g = Graph.FromSmiles("cccc");
Matching m = Matching.CreateEmpty(g);
m.Match(1, 2);
// no vertex '3' matching can not be improved
MaximumMatching.Maximise(g, m, 2, IntSet.AllOf(0, 1, 2));
Assert.IsTrue(Compares.AreOrderLessDeepEqual(
new[] { Tuple.Of(1, 2) },
m.GetMatches()));
}
/// <summary>
/// When precisely two vertices are unmatched we only need to find a single
/// augmenting path. Rather than run through edmonds with blossoms etc we
/// simple do a targest DFS for the path.
///
/// <param name="g">graph</param>
/// <param name="m">matching</param>
/// <param name="nMatched">current matching cardinality must be |s|-nMathced == 2</param>
/// <param name="s">subset size</param>
/// <returns>new match cardinality</returns>
/// </summary>
public static int AugmentOnce(Graph g, Matching m, int nMatched, BitArray s)
{
int vStart = BitArrays.NextSetBit(s, 0);
while (vStart >= 0)
{
if (!m.Matched(vStart))
{
break;
}
vStart = BitArrays.NextSetBit(s, vStart + 1);
}
int vEnd = BitArrays.NextSetBit(s, vStart + 1);
while (vEnd >= 0)
{
if (!m.Matched(vEnd))
{
break;
}
vEnd = BitArrays.NextSetBit(s, vEnd + 1);
}
// find an augmenting path between vStart and vEnd
int[] path = new int[g.Order];
int len = FindPath(g, vStart, vEnd, s, path, 0, m, false);
if (len > 0)
{
// augment
for (int i = 0; i < len; i += 2)
{
m.Match(path[i], path[i + 1]);
}
nMatched += 2;
}
return(nMatched);
}
public static int DfsVisit(Graph g, int v, Matching m, BitArray unvisited, bool match)
{
unvisited.Set(v, false);
int nMatched = 0;
int d = g.Degree(v);
while (--d >= 0)
{
int w = g.EdgeAt(v, d).Other(v);
if (unvisited[w])
{
if (match)
{
m.Match(v, w);
return(2 + DfsVisit(g, w, m, unvisited, false));
}
else
{
nMatched += DfsVisit(g, w, m, unvisited, true);
}
}
}
return(nMatched);
}
