double fitnessFunction(BitArray representation)
{
MinimalSpanningTree mst = dnaToMst(representation);
// This is the bottleneck, quite obviously.
mst.Span(startFrom: startNodes);
int usedNodes = mst.UsedNodeCount;
// TODO: Investigate fitness function
return(1500 - usedNodes);
}
/// <summary>
/// Tells the genetic algorithm to advance one generation and processes
/// the resulting (possibly) improved solution.
/// </summary>
public void EvolutionStep()
{
if (!_initialized)
{
throw new InvalidOperationException("Solver not initialized!");
}
ga.NewGeneration();
if ((_bestDNA == null) || (GeneticAnnealingAlgorithm.SetBits(ga.GetBestDNA().Xor(_bestDNA)) != 0))
{
_bestDNA = ga.GetBestDNA();
MinimalSpanningTree bestMst = dnaToMst(_bestDNA);
bestMst.Span(startFrom: startNodes);
// #DEBUG#: Pass true to show the used steiner nodes.
BestSolution = SpannedMstToSkillnodes(bestMst, false);
}
}
public void TestMST()
{
/// 0 -- 1 -- 2 -- 3
/// \ | /
/// \ | /
/// 4 -- 5 -- 6 -- 7
bool[,] graph1 = {
{ false, true, false, false, true, false, false, false },
{ true, false, true, false, false, false, false, false },
{ false, true, false, true, false, true, false, false },
{ false, false, true, false, false, true, false, false },
{ true, false, false, false, false, true, false, false },
{ false, false, true, true, true, false, true, false },
{ false, false, false, false, false, true, false, true },
{ false, false, false, false, false, false, true, false },
};
SearchGraph searchGraph1 = SearchGraphFromData(graph1);
Dictionary<int, GraphNode> graphNodes1 = GetGraphNodesIdIndex(searchGraph1);
DistanceLookup distanceLookup = new DistanceLookup();
HashSet<GraphNode> mstNodes1 = new HashSet<GraphNode>
{ graphNodes1[3], graphNodes1[5], graphNodes1[7] };
MinimalSpanningTree mst1 = new MinimalSpanningTree(mstNodes1);
mst1.Span(startFrom: graphNodes1[0]);
Assert.IsTrue(mst1.SpanningEdges.Count == 3, "Wrong amount of spanning edges");
/// This can fail even if the mst would be valid! The test only works for
/// the current implementation of the mst algorithm, but I can't find a
/// better way to do this with the current data structures...
Assert.IsTrue(mst1.SpanningEdges[0].inside.Id == 0 && mst1.SpanningEdges[0].outside.Id == 5,
"First edge is wrong");
Assert.IsTrue(mst1.SpanningEdges[1].inside.Id == 5 && mst1.SpanningEdges[1].outside.Id == 3,
"Second edge is wrong");
Assert.IsTrue(mst1.SpanningEdges[2].inside.Id == 5 && mst1.SpanningEdges[2].outside.Id == 7,
"Third edge is wrong");
Assert.IsTrue(mst1.UsedNodeCount == 5, "Wrong MST length");
/// Test unconnected graph
/// 0 -- 1 2 -- 3
/// | /
/// | /
/// 4 -- 5
bool[,] graph2 = {
{ false, true, false, false, false, false },
{ true, false, false, false, false, false },
{ false, false, false, true, false, true },
{ false, false, true, false, false, true },
{ false, false, false, false, false, true },
{ false, false, true, true, true, false },
};
SearchGraph searchGraph2 = SearchGraphFromData(graph2);
Dictionary<int, GraphNode> graphNodes2 = GetGraphNodesIdIndex(searchGraph2);
HashSet<GraphNode> mstNodes2 = new HashSet<GraphNode> { graphNodes2[0], graphNodes2[2], graphNodes2[4] };
bool pass = false;
try
{
MinimalSpanningTree mst = new MinimalSpanningTree(mstNodes2);
mst.Span(graphNodes2[3]);
}
catch (DistanceLookup.GraphNotConnectedException)
{
pass = true;
}
Assert.IsTrue(pass, "No exception thrown for disconnected graph");
}
/// <summary>
/// Finds the nodes in the search graph that can be potential steiner
/// nodes. Those form the search space base.
/// </summary>
private void buildSearchSpaceBase()
{
searchSpaceBase = new List<GraphNode>();
MinimalSpanningTree leastSolution = new MinimalSpanningTree(targetNodes, distances);
leastSolution.Span(startFrom: startNodes);
int maxEdgeDistance = 0;
foreach (GraphEdge edge in leastSolution.SpanningEdges)
{
int edgeDistance = distances.GetDistance(edge);
if (edgeDistance > maxEdgeDistance)
maxEdgeDistance = edgeDistance;
}
/*
int maxTargetDistance = 0;
foreach (GraphNode targetNode in targetNodes)
{
int targetDistance = distances.GetDistance(targetNode, startNodes);
if (targetDistance > maxTargetDistance)
maxTargetDistance = targetDistance;
}*/
// Find potential steiner points that are in reasonable vicinity.
/// TODO: This can surely be improved in some shape or form, but I
/// can't figure it out right now. Since the GA also has to work well
/// with larger input sizes, I won't investigate this right now.
foreach (GraphNode node in searchGraph.nodeDict.Values)
{
// This can be a steiner node only if it has more than 2 neighbors.
if (node.Adjacent.Count > 2)
{
/*
* While this would mathematically be correct, it's not a
* good criterium for the skill tree. I don't think the
* relevant cases can appear and this permits way too many
* nodes to be considered that will never be included in an
* actual solution.
*
/// If every target node is closer to the start than to a certain
/// steiner node, that node can't be needed for the steiner tree.
bool add = false;
foreach (GraphNode targetNode in targetNodes)
if (distances.GetDistance(targetNode, node) < distances.GetDistance(targetNode, startNodes))
add = true;
if (add)
searchSpaceBase.Add(node);
*/
/*
/// This is a pretty handwavy approach... If anybody figures
/// out a case that causes this to fail, let me know please!
if (distances.GetDistance(node, startNodes) < 1.2 * maxTargetDistance)
searchSpaceBase.Add(node);
*/
// This should be a reasonable approach.
bool add = false;
foreach (GraphNode targetNode in targetNodes)
if (distances.GetDistance(targetNode, node) < maxEdgeDistance)
add = true;
if (add)
searchSpaceBase.Add(node);
}
}
/* ONLY FOR WHEN NODES HAVE INDIVIDUAL WEIGHTS
* foreach (ushort nodeId in targetSkillnodes)
{
searchSpaceBase.Add(SkillTree.Skillnodes[nodeId]);
}*/
}
/// <summary>
/// Converts an MST spanning a set of GraphNodes back into its equivalent
/// as a HashSet of SkillNode IDs.
/// </summary>
/// <param name="mst">The spanned MinimalSpanningTree.</param>
/// <param name="visualize">A debug parameter that highlights all used
/// GraphNodes' SkillNode equivalents in the tree.</param>
/// <returns>A HashSet containing the node IDs of all SkillNodes spanned
/// by the MST.</returns>
HashSet <ushort> SpannedMstToSkillnodes(MinimalSpanningTree mst, bool visualize)
{
if (!mst.IsSpanned)
{
throw new Exception("The passed MST is not spanned!");
}
HashSet <ushort> newSkilledNodes = new HashSet <ushort>();
foreach (GraphEdge edge in mst.SpanningEdges)
{
ushort target = edge.outside.Id;
HashSet <ushort> start;
if (edge.inside is Supernode)
{
start = tree.SkilledNodes;
}
else
{
start = new HashSet <ushort>()
{
edge.inside.Id
}
};
var path = tree.GetShortestPathTo(target, start);
newSkilledNodes = new HashSet <ushort>(newSkilledNodes.Concat(path));
}
if (visualize)
{
tree._nodeHighlighter.UnhighlightAllNodes(NodeHighlighter.HighlightState.FromAttrib);
foreach (GraphNode steinerNode in mst.mstNodes)
{
tree._nodeHighlighter.HighlightNode(SkillTree.Skillnodes[steinerNode.Id], NodeHighlighter.HighlightState.FromAttrib);
}
}
//tree.DrawHighlights(tree._nodeHighlighter);
return(newSkilledNodes);
}
MinimalSpanningTree dnaToMst(BitArray dna)
{
List <GraphNode> usedSteinerPoints = new List <GraphNode>();
for (int i = 0; i < dna.Length; i++)
{
if (dna[i])
{
usedSteinerPoints.Add(searchSpaceBase[i]);
}
}
HashSet <GraphNode> mstNodes = new HashSet <GraphNode>(usedSteinerPoints);
mstNodes.Add(startNodes);
foreach (GraphNode targetNode in targetNodes)
{
mstNodes.Add(targetNode);
}
return(new MinimalSpanningTree(mstNodes, distances));
}
double fitnessFunction(BitArray representation)
{
MinimalSpanningTree mst = dnaToMst(representation);
// This is the bottleneck, quite obviously.
mst.Span(startFrom: startNodes);
int usedNodes = mst.UsedNodeCount;
// TODO: Investigate fitness function
return(1500 - usedNodes);
}
}
/// <summary>
/// Finds the nodes in the search graph that can be potential steiner
/// nodes. Those form the search space base.
/// </summary>
private void buildSearchSpaceBase()
{
searchSpaceBase = new List <GraphNode>();
MinimalSpanningTree leastSolution = new MinimalSpanningTree(targetNodes, distances);
leastSolution.Span(startFrom: startNodes);
int maxEdgeDistance = 0;
foreach (GraphEdge edge in leastSolution.SpanningEdges)
{
int edgeDistance = distances.GetDistance(edge);
if (edgeDistance > maxEdgeDistance)
{
maxEdgeDistance = edgeDistance;
}
}
/*
* int maxTargetDistance = 0;
* foreach (GraphNode targetNode in targetNodes)
* {
* int targetDistance = distances.GetDistance(targetNode, startNodes);
* if (targetDistance > maxTargetDistance)
* maxTargetDistance = targetDistance;
* }*/
// Find potential steiner points that are in reasonable vicinity.
/// TODO: This can surely be improved in some shape or form, but I
/// can't figure it out right now. Since the GA also has to work well
/// with larger input sizes, I won't investigate this right now.
foreach (GraphNode node in searchGraph.nodeDict.Values)
{
// This can be a steiner node only if it has more than 2 neighbors.
if (node.Adjacent.Count > 2)
{
/*
* While this would mathematically be correct, it's not a
* good criterium for the skill tree. I don't think the
* relevant cases can appear and this permits way too many
* nodes to be considered that will never be included in an
* actual solution.
*
* /// If every target node is closer to the start than to a certain
* /// steiner node, that node can't be needed for the steiner tree.
* bool add = false;
* foreach (GraphNode targetNode in targetNodes)
* if (distances.GetDistance(targetNode, node) < distances.GetDistance(targetNode, startNodes))
* add = true;
* if (add)
* searchSpaceBase.Add(node);
*/
/*
* /// This is a pretty handwavy approach... If anybody figures
* /// out a case that causes this to fail, let me know please!
* if (distances.GetDistance(node, startNodes) < 1.2 * maxTargetDistance)
* searchSpaceBase.Add(node);
*/
// This should be a reasonable approach.
bool add = false;
foreach (GraphNode targetNode in targetNodes)
{
if (distances.GetDistance(targetNode, node) < maxEdgeDistance)
{
add = true;
}
}
if (add)
{
searchSpaceBase.Add(node);
}
}
}
/* ONLY FOR WHEN NODES HAVE INDIVIDUAL WEIGHTS
* foreach (ushort nodeId in targetSkillnodes)
* {
* searchSpaceBase.Add(SkillTree.Skillnodes[nodeId]);
* }*/
}