public QapAntAlgorithm(int pheromoneInc, int extraPheromoneInc, int nAnts, int maxIterations, int maxIterationsNoChanges)
{
NAnts = nAnts;
PheromoneInc = pheromoneInc;
ExtraPheromoneInc = extraPheromoneInc;
MaxIterations = maxIterations;
MaxIterationsNoChanges = maxIterationsNoChanges;
BestAnt = new QapAnt {PathCost = int.MaxValue, VisitedVetecies = new List<IVertex>()};
}
public void Run()
{
_currentAnt = new QapAnt();
_currentIteration = 0;
_currentIterationNoChanges = 0;
BestAnt = new QapAnt {PathCost = Int32.MaxValue, VisitedVetecies = new List<IVertex>()};
_resultBuilder = new StringBuilder();
_resultBuilder.Append("Start\n");
while (!IsFinished())
{
CreateAnts();
IList<IVertex> newPath = AntsTravel();
_currentAnt = new QapAnt {VisitedVetecies = newPath, PathCost = 0};
ComputePathCost(_currentAnt);
LocalSearch(_currentAnt);
if (!IsNewBestPath(_currentAnt))
{
_currentIterationNoChanges++;
}
else _currentIterationNoChanges = 0;
UpdateGeneration();
_currentIteration++;
Ants.Clear();
}
}
public void LocalSearch(QapAnt ant)
{
// set of moves, numbered from 0 to index
int[] move = new int[Ants.Count * (Ants.Count - 1) / 2];
int nMoves = 0;
for (int i = 0; i < Ants.Count - 1; i++)
{
for (int j = i + 1; j < Ants.Count; j++)
{
move[nMoves++] = Ants.Count * i + j;
}
}
bool isImproved = true;
for (int scan = 0; scan < 2 && isImproved; scan++)
{
isImproved = false;
for (int i = 0; i < nMoves - 1; i++)
{
int x = GetPermutationalIndex(i + 1, nMoves - 1);
int y = move[i];
move[i] = move[x];
move[x] = y;
}
for (int i = 0; i < nMoves; i++)
{
int r = move[i] / Ants.Count;
int s = move[i] % Ants.Count;
int moveCost = ComputeMoveCost(r, s, ant.VisitedVetecies);
if (moveCost < 0)
{
ant.PathCost += moveCost;
int y = ant.VisitedVetecies[r].Number;
ant.VisitedVetecies[r].Number = ant.VisitedVetecies[s].Number;
ant.VisitedVetecies[s].Number = y;
isImproved = true;
}
}
}
}
public bool IsNewBestPath(QapAnt ant)
{
int bestOne = BestAnt.PathCost;
int newOne = ant.PathCost;
if (newOne < bestOne)
{
_flag = 2;
BestAnt.VisitedVetecies = (IList<IVertex>)DeepObjectClone(ant.VisitedVetecies);
BestAnt.PathCost = ant.PathCost;
NewResultUpdate();
return true;
}
if (newOne == bestOne)
{
_flag = 1;
}
else
{
_flag = 0;
}
return false;
}
public int ComputePathCost(QapAnt ant)
{
int cost = 0;
for (int i = 0; i < ant.VisitedVetecies.Count; i++)
{
for (int j = 0; j < ant.VisitedVetecies.Count; j++)
{
cost += (int) (Graph.Edges[i, j].Mark.Path.Value *
Graph.Flows[ant.VisitedVetecies[i].Number, ant.VisitedVetecies[j].Number]);
}
}
ant.PathCost = cost;
return cost;
}
