private TSPSolution getShortestTour()
{
double lowestCost = Double.PositiveInfinity;
Ant lowestAnt = null;
foreach (Ant ant in ants)
{
if (ant.getFinalTourLength(Cities) < lowestCost)
{
lowestCost = ant.getFinalTourLength(Cities);
lowestAnt = ant;
}
}
if (lowestAnt == null)
{
return(null);
}
return(new TSPSolution(indexToCities(Cities, lowestAnt.pathSoFar)));
}
private Edge NextEdge(Ant ant)
{
double c = 0;
double r = random.NextDouble();
Vertex vertex = ant.visitedVertices.Peek();
foreach (Edge e in vertex.neighbors)
{
if (!ant.visitedVertices.Contains(e.vertex2))
{
c += Probability(ant, e);
if (c >= r)
{
return(e);
}
}
}
return(null);
}
private void AntPath(Ant ant)
{
counter = 0;
AntPathRecurring(ant, ant.startVertex);
}
public void antSolve()
{
timer = new Stopwatch();
timer.Start();
//BASF = Best Ant So Far
Ant BASF, bestAnt, worstAnt;
Edge[,] matrix = generateCostMatrix();
do
{
BASF = new Ant(ref matrix);
} while (!(BASF.IsComplete));
//I found that these were good values.
double MIN_IMPROVEMENT = .70;
int MAX_REDUNDANT_ITERATIONS = 25;
int redundant_iterations = 0;
while (redundant_iterations < MAX_REDUNDANT_ITERATIONS)
{
do
{
bestAnt = new Ant(ref matrix);
} while (!bestAnt.IsComplete);
worstAnt = bestAnt;
//send out ants!
//With only two ants, two sets of edges will be either increased or decayed. Edges occuring in both solutions will be slightly decremented.
for (int j = 1; j < 2; j++)
{
Ant ant = new Ant(ref matrix);
if (ant.IsComplete)
{
if (ant.TotalCost < bestAnt.TotalCost)
bestAnt = ant;
else if (ant.TotalCost > worstAnt.TotalCost)
worstAnt = ant;
}
}
bestAnt.updatePheromones(false);
worstAnt.updatePheromones(true);
//improvement represents the ratio of this ant's journey to the current best.
double improvement = bestAnt.TotalCost / BASF.TotalCost;
if (improvement < 1)
BASF = bestAnt;
if (improvement > MIN_IMPROVEMENT)
redundant_iterations++;
}
// call this the best solution so far. bssf is the route that will be drawn by the Draw method.
Route = new ArrayList(Cities.Length);
for (int i = 0; i < BASF.Route.Count; i++)
Route.Add(Cities[BASF.Route[i]]);
bssf = new TSPSolution(Route);
// update the cost of the tour.
TimeSpan ts = timer.Elapsed;
// do a refresh.
Program.MainForm.tbCostOfTour.Text = " " + bssf.costOfRoute();
Program.MainForm.tbElapsedTime.Text = ts.TotalSeconds.ToString();
Program.MainForm.Invalidate();
}
public void antSolve()
{
timer = new Stopwatch();
timer.Start();
//BASF = Best Ant So Far
Ant BASF, bestAnt, worstAnt;
Edge[,] matrix = generateCostMatrix();
do
{
BASF = new Ant(ref matrix);
} while (!(BASF.IsComplete));
//I found that these were good values.
double MIN_IMPROVEMENT = .70;
int MAX_REDUNDANT_ITERATIONS = 25;
int redundant_iterations = 0;
while (redundant_iterations < MAX_REDUNDANT_ITERATIONS)
{
do
{
bestAnt = new Ant(ref matrix);
} while (!bestAnt.IsComplete);
worstAnt = bestAnt;
//send out ants!
//With only two ants, two sets of edges will be either increased or decayed. Edges occuring in both solutions will be slightly decremented.
for (int j = 1; j < 2; j++)
{
Ant ant = new Ant(ref matrix);
if (ant.IsComplete)
{
if (ant.TotalCost < bestAnt.TotalCost)
{
bestAnt = ant;
}
else if (ant.TotalCost > worstAnt.TotalCost)
{
worstAnt = ant;
}
}
}
bestAnt.updatePheromones(false);
worstAnt.updatePheromones(true);
//improvement represents the ratio of this ant's journey to the current best.
double improvement = bestAnt.TotalCost / BASF.TotalCost;
if (improvement < 1)
{
BASF = bestAnt;
}
if (improvement > MIN_IMPROVEMENT)
{
redundant_iterations++;
}
}
// call this the best solution so far. bssf is the route that will be drawn by the Draw method.
Route = new ArrayList(Cities.Length);
for (int i = 0; i < BASF.Route.Count; i++)
{
Route.Add(Cities[BASF.Route[i]]);
}
bssf = new TSPSolution(Route);
// update the cost of the tour.
TimeSpan ts = timer.Elapsed;
// do a refresh.
Program.MainForm.tbCostOfTour.Text = " " + bssf.costOfRoute();
Program.MainForm.tbElapsedTime.Text = ts.TotalSeconds.ToString();
Program.MainForm.Invalidate();
}
public void doCircut(Ant ant)
{
ant.visitCity(rand.Next(0, Cities.Length));
for (int i = 0; i < Cities.Length - 1; i++)
{
if (rand.NextDouble() < RANDOM_CHANCE)
{
int t = rand.Next(Cities.Length - ant.getCurrentCity()); // random town
int j = -1;
for (int k = 0; k < Cities.Length; k++)
{
if (!ant.citiesVisited[k])
{
j++;
}
if (j == t)
{
ant.visitCity(k);
break;
}
}
}
double[] probs = new double[Cities.Length];
double denom = 0.0;
for (int j = 0; j < Cities.Length; j++)
{
if (ant.citiesVisited[j])
{
probs[j] = 0.0;
}
else
{
probs[j] = getProbability(ant.getCurrentCity(), j);
}
denom += probs[j];
}
if (denom == 0)
{
ant = new Ant(Cities.Length);
doCircut(ant);
if (ant.pathSoFar.Count < Cities.Length)
{
finishPath(ant);
return;
}
return;
}
for (int j = 0; j < Cities.Length; j++)
{
probs[j] /= denom;
}
double r = rand.NextDouble();
double total = 0.0;
for (int j = 0; j < Cities.Length; j++)
{
total += probs[j];
if (total >= r)
{
ant.visitCity(j);
break;
}
}
}
if (ant.pathSoFar.Count < Cities.Length)
{
finishPath(ant);
return;
}
}
/*
* Clears out the ant's path.
* The ant's new path is then started at a random city.
*/
private void ResetAnt(Ant ant)
{
ant.Path.Clear();
ant.Visited.Clear();
ant.Add(random.Next(0, Cities.Length));
}
public string[] fancySolveProblem()
{
string[] results = new string[3];
int count = 0;
Stopwatch timer = new Stopwatch();
Ant[] ants = new Ant[Cities.Length];
//Initialize with empty ants
for (int i = 0; i < Cities.Length; i++)
{
ants[i] = new Ant();
ants[i].Add(i);
}
distances = CalculateInitialMatrix();
pheromones = new double[Cities.Length, Cities.Length];
for (int i = 0; i < Cities.Length; i++)
{
for (int j = 0; j < Cities.Length; j++)
{
pheromones[i, j] = 1;
}
}
int iterations = 0;
timer.Start();
/*
* While we are not out of time and still seeing changes,
* The ants all select the best edge out of current city.
* This is done using the distance and pheromone of the edge.
* When a completed tour is found, it is compared to the BSSF.
* If the tour is better the BSSF is updated.
* The existing, older pheromones fade by a constant factor,
* and additional pheromone is placed on the new tour.
* After this an ant with a completed tour is reset.
*/
while (timer.Elapsed.TotalMilliseconds < time_limit && iterations < ITERATION_THRESHOLD)
{
for (int i = 0; i < Cities.Length; i++)
{
for (int j = 0; j < Cities.Length; j++)
{
if (ants[j].Count == Cities.Length)
{
if (Cities[ants[j].Path[ants[j].Count - 1]].costToGetTo(Cities[ants[j].Path[0]]) != double.PositiveInfinity)
{
TSPSolution potentialSolution = GenerateRoute(ants[j].Path);
double costOfRoute = potentialSolution.costOfRoute();
if (bssf == null || costOfRoute < costOfBssf())
{
iterations = 0;
bssf = potentialSolution;
count++;
}
FadePheromone();
DropPheromone(ants[j], costOfRoute);
}
ResetAnt(ants[j]);
}
TakeNextEdge(ants[j]);
}
}
iterations++;
}
timer.Stop();
results[COST] = costOfBssf().ToString();
results[TIME] = timer.Elapsed.ToString();
results[COUNT] = count.ToString();
Console.WriteLine("Ant Colony Size: " + Cities.Length + " Random: " + Seed + " Path: " + costOfBssf().ToString() + " Time: " + timer.Elapsed.ToString());
return(results);
}
public void groupTSP()
{
// start our timer
System.Diagnostics.Stopwatch timer = new System.Diagnostics.Stopwatch();
timer.Start();
// constants used in heuristics
const int ITERATIONS = 50;
const double Q0 = 0.9;
const double BETA = 50.0;
const double ALPHA = 0.1;
// get cost from nearest neighbor, used in our heuristic
greedy();
double nnCost = costOfBssf();
// our fastest ant through all the iterations
Ant bestAnt = null;
double bestCost = Double.PositiveInfinity;
// initialize pheramone level matrix
double[,] pheromoneLevels = new double[Cities.Length, Cities.Length];
for (int i = 0; i < Cities.Length; i++)
{
for (int j = 0; j < Cities.Length; j++)
{
pheromoneLevels[i, j] = 1.0 / Cities.Length;
}
}
// start iterations
for (int h = 0; h < ITERATIONS; h++)
{
// our fastest ant in the iteration
Ant bestAntIter = null;
double bestCostIter = Double.PositiveInfinity;
// initialize ants
List <Ant> ants = new List <Ant>();
for (int i = 0; i < Cities.Length; i++)
{
ants.Add(new Ant(Cities.Length, i));
}
// iterate through each time step
for (int i = 0; i < Cities.Length - 1; i++)
{
// determine each ants next move
List <Ant> remainingAnts = new List <Ant>(ants);
foreach (Ant ant in remainingAnts)
{
int nextCity = -1;
double nextDistance = Double.PositiveInfinity;
Random random = new Random();
double q = random.NextDouble();
if (q < Q0)
{
// select next city based on distance / pheramone only
double bestScore = Double.NegativeInfinity;
foreach (int city in ant.unvisited)
{
double distance = Cities[ant.curCity].costToGetTo(Cities[city]);
double score = pheromoneLevels[ant.curCity, city] * Math.Pow(1 / distance, BETA);
if (score > bestScore)
{
nextCity = city;
bestScore = score;
nextDistance = distance;
}
}
}
else
{
// select city randomly with different weights given to each city based on distance / pheramone
double runningTotal = 0.0;
double randomValue = random.NextDouble();
// get sum of scores
double summedScores = 0.0;
foreach (int city in ant.unvisited)
{
double distance = Cities[ant.curCity].costToGetTo(Cities[city]);
summedScores += pheromoneLevels[ant.curCity, city] * Math.Pow(1 / distance, BETA);
}
// determine probability for each city
foreach (int city in ant.unvisited)
{
double distance = Cities[ant.curCity].costToGetTo(Cities[city]);
runningTotal += (pheromoneLevels[ant.curCity, city] * Math.Pow(1 / distance, BETA)) / summedScores;
if (runningTotal > randomValue)
{
nextCity = city;
nextDistance = distance;
break;
}
}
}
if (nextCity != -1)
{
// apply local trail updating
pheromoneLevels[ant.curCity, nextCity] += (1 - ALPHA) * pheromoneLevels[ant.curCity, nextCity] + ALPHA * (1 / (Cities.Length * nnCost));
// add the picked city to the tour
ant.tour[ant.curCity] = nextCity;
ant.unvisited.Remove(nextCity);
ant.curCost += nextDistance;
ant.prevCity = ant.curCity;
ant.curCity = nextCity;
}
else
{
//deal with stuck ant
ants.Remove(ant);
}
}
}
// finalize tours and find best ant
foreach (Ant ant in ants)
{
// finalize tour
ant.tour[ant.curCity] = ant.startCity;
ant.curCost += Cities[ant.curCity].costToGetTo(Cities[ant.startCity]);
// check against current best cost
if (ant.curCost < bestCostIter)
{
bestAntIter = ant;
bestCostIter = ant.curCost;
}
}
if (bestAntIter != null)
{
// apply global trail updating
int current = bestAntIter.startCity;
do
{
pheromoneLevels[current, bestAntIter.tour[current]] += (1 - ALPHA) * pheromoneLevels[current, bestAntIter.tour[current]] + ALPHA * (1 / bestCostIter);
current = bestAntIter.tour[current];
} while (current != bestAntIter.startCity);
// see if it is the best ant through all iterations so far
if (bestCostIter < bestCost)
{
bestAnt = bestAntIter;
bestCost = bestCostIter;
}
}
}
if (bestAnt != null)
{
ArrayList route = new ArrayList();
int curCity = bestAnt.startCity;
do
{
route.Add(Cities[curCity]);
curCity = bestAnt.tour[curCity];
} while (curCity != bestAnt.startCity);
bssf = new TSPSolution(route);
}
timer.Stop();
Program.MainForm.tbCostOfTour.Text = " " + bssf.costOfRoute();
Program.MainForm.tbElapsedTime.Text = Convert.ToString(timer.Elapsed);
// do a refresh.
Program.MainForm.Invalidate();
}
