//public IEnumerable<List<int>> EnumerateMIS(Graph graph)
//{
// var primaryGraph = new GraphFast(graph);
// var complementaryGraph = new GraphFast(graph);
// var ignoredVertex = new bool[graph.VerticesKVPs.Length];
// var verticesAlreadyInMIS = new List<int>();
// foreach (var mis in FindMIS(primaryGraph, complementaryGraph, verticesAlreadyInMIS, ignoredVertex, 0))
// {
// yield return mis.vertices;
// }
//}
private Solution Recurse(int n, GraphFast primaryGraph, GraphFast complementaryGraph, Solution currentSolution, Solution bestSolution, int latestMisSize = int.MaxValue, int lastMisId = int.MaxValue)
{
if (complementaryGraph.vertexCount == 0)
{
if (currentSolution.colourCount < bestSolution.colourCount)
{
bestSolution = currentSolution.DeepClone();
NewBestSolutionFound?.Invoke(null, new PerformanceReport()
{
minimalNumberOfColoursUsed = bestSolution.colourCount,
elapsedProcessorTime = stopwatch.Elapsed
});
}
}
else if (currentSolution.colourCount + 1 < bestSolution.colourCount) // could improve this bound by finding a clique
{
// get MIS get and complimentary graph
// compute subsolution
var verticesAlreadyInMIS = new List <int>();
currentSolution.colourCount += 1;
var ignoredVertex = new bool[n];
FindMIS(primaryGraph, complementaryGraph, verticesAlreadyInMIS, ignoredVertex, 0, mis =>
{
// optionally check for cliques to delete
if (mis.vertices.Count < latestMisSize || (mis.vertices.Count == latestMisSize && mis.vertices[0] > lastMisId))// pre-optimization
{
currentSolution.colourLayer.Push(mis.vertices);
bestSolution = Recurse(n, complementaryGraph, complementaryGraph.DeepIrreversibleClone(), currentSolution, bestSolution, mis.vertices.Count, mis.vertices[0]);
currentSolution.colourLayer.Pop();
}
// need to fix the enumerator to ensure breakability
return(currentSolution.colourCount < bestSolution.colourCount);
});
currentSolution.colourCount -= 1;
}
return(bestSolution);
}
private Solution Recurse(Graph graphToColour, Solution currentSolution, Solution bestSolution, ref int upperBoundOnNumberOfSteps, double alphaRatio, int maxDepth)
{
if (upperBoundOnNumberOfSteps != -1 && bestSolution.colourCount < int.MaxValue)
{
if (upperBoundOnNumberOfSteps == 0)
{
return(bestSolution);
}
else
{
upperBoundOnNumberOfSteps -= 1;
}
}
if (currentSolution.solvedCount < graphToColour.VerticesKVPs.Length)
{
// choose a vertex to colour
var vertexToColour = ChooseSuitableVertex(graphToColour, currentSolution, bestSolution, out var colouringPossibilities, maxDepth);
// for in possible colours
foreach (var colour in colouringPossibilities)
{
var increasedColourCount = false;
if (colour >= currentSolution.colourCount)
{
if (colour > currentSolution.colourCount)
{
throw new Exception("New colour is too large");
}
currentSolution.colourCount += 1;
increasedColourCount = true;
}
if (currentSolution.colourCount * alphaRatio < bestSolution.colourCount)
{
currentSolution.vertexToColour[vertexToColour] = colour;
currentSolution.solvedCount += 1;
// recurse and update best statistics
bestSolution = Recurse(graphToColour, currentSolution, bestSolution, ref upperBoundOnNumberOfSteps, alphaRatio, maxDepth);
currentSolution.solvedCount -= 1;
currentSolution.vertexToColour[vertexToColour] = -1;
}
if (increasedColourCount)
{
currentSolution.colourCount -= 1;
}
}
}
else
{
// no more vertices to colour
// if the solution is indeed better...
if (currentSolution.colourCount >= bestSolution.colourCount)
{
throw new Exception("Proposed solution is not better");
}
// warning! there may be vertices with negative colourings!
bestSolution = currentSolution.DeepClone();
NewBestSolutionFound?.Invoke(null, new PerformanceReport()
{
minimalNumberOfColoursUsed = bestSolution.colourCount,
elapsedProcessorTime = stopwatch.Elapsed
});
}
return(bestSolution);
}
