protected override void PerformMutation(IGraphChromosome graph, float probability)
{
if (RandomizationProvider.Current.GetDouble() >= probability)
{
return;
}
// No edges to add
if (graph.EdgeCount == graph.VertexCount * graph.VertexCount)
{
return;
}
// Shuffle
var allIDs = graph.Vertices.Select(v => v.ID);
uint[] fromVerts = MutationService.Shuffle(allIDs, RandomizationProvider.Current).ToArray();
uint[] toVerts = MutationService.Shuffle(allIDs, RandomizationProvider.Current).ToArray();
// Find the first that does not exist
foreach (var v1 in fromVerts)
{
foreach (var v2 in toVerts)
{
if (!graph.ContainsEdge(v1, v2))
{
graph.AddEdge(v1, v2, graph.CreateNewEdge());
return;
}
}
}
}
/// <summary>
/// Calculates the total distance between two graphs, only
/// accounting for edges.
/// </summary>
/// <param name="g1"></param>
/// <param name="g2"></param>
/// <returns></returns>
protected double TotalEdgeDistance(IGraphChromosome g1, IGraphChromosome g2)
{
double totalDist = 0;
double nMismatch = 0;
double nMatch = 0;
foreach (var edge in g1.Edges)
{
if (g2.ContainsEdge(edge.IDFrom, edge.IDTo))
{
totalDist += EdgeDistance(g2[edge.IDFrom, edge.IDTo], edge.Value);
nMatch++;
}
else
{
nMismatch++;
}
}
foreach (var edge in g2.Edges)
{
if (!g1.ContainsEdge(edge.IDFrom, edge.IDTo))
{
nMismatch++;
}
}
int N = Math.Max(g1.EdgeCount, g2.EdgeCount);
return((EdgeMismatchWeight * nMismatch / N) + (EdgeMatchWeight * totalDist / nMatch));
}
protected override IGraphChromosome PerformCrossover(IGraphChromosome p1, IGraphChromosome p2)
{
IList <IChromosome> parents = new IChromosome[2];
// "Disjoint genes are inherited from the more fit parent."
var child = p1.Clone() as IGraphChromosome;
foreach (var vert in p1.Vertices)
{
if (p2.ContainsVertex(vert.ID))
{
parents[0] = vert.Value;
parents[1] = p2[vert.ID];
child[vert.ID] = VertexCrossover.Cross(parents)[0];
}
}
foreach (var edge in p1.Edges)
{
if (p2.ContainsEdge(edge.IDFrom, edge.IDTo))
{
parents[0] = edge.Value;
parents[1] = p2[edge.IDFrom, edge.IDTo];
child[edge.IDFrom, edge.IDTo] = EdgeCrossover.Cross(parents)[0];
}
}
return(child);
}