public void findGreatestDiff(State state) //O(n^3)
{
int chosenX = 0; //city x to city y
int chosenY = 0;
double greatestDiff = double.NegativeInfinity; //initialize to -oo to find what the greatest
//difference is
List <PointF> points = new List <PointF>();
for (int i = 0; i < state.getMap().GetLength(0); i++) //rows, O(n)
{
for (int j = 0; j < state.getMap().GetLength(1); j++) //columns
{
if (state.getPoint(i, j) == 0) //if point is 0
{
points.Add(new PointF(i, j)); //store all 0's in a point array
}
}
}
for (int i = 0; i < points.Count; i++) //loop through 0's to find the greatest difference
{ //O(n^3) there will be atmost n points, because the entire
//matrix will be 0
int possibleMax = findExcludeMinusInclude(Convert.ToInt32(points[i].X), Convert.ToInt32(points[i].Y), state); //O(n^2)
if (possibleMax >= greatestDiff) //set the point to point values, if it is 0 is covered by =
{
chosenX = Convert.ToInt32(points[i].X);
chosenY = Convert.ToInt32(points[i].Y);
greatestDiff = possibleMax;
}
}
State include = makeInclude(chosenX, chosenY, state); //O(n^2)
if (BSSF > include.getLB()) //if include's lowerbound is better than the BSSF
{
include.setEdge(chosenX, chosenY); //set the edge in the dictionary
checkCycles(include, chosenX, chosenY); //O(n), make sure there are no potential cycles
queue.Add(include); //add to the queue to be popped off later
}
if (isDictionaryFilled(include)) //O(n), have all of the edges been filled? then the include.LB is better
{ //than the current BSSF, set the BSSF
BSSF = include.getLB();
bestState = include; //save the "bestState"
}
State exclude = makeExclude(chosenX, chosenY, state); //O(n^2)
if (BSSF > exclude.getLB()) //if exclude's lowerbound is than the BSSF, add it to the queue
{
queue.Add(exclude);
}
if (isDictionaryFilled(exclude)) //O(n), have all of the edges been filled?
{ // then exclude's lowerbound is better, set the BSSF to exclude.LB
BSSF = exclude.getLB();
bestState = exclude;
}
}
public State makeExclude(int x, int y, State state) //O(n^2)
{
State excludeState = new State(copyMatrix(state.getMap()), state.getLB(), state.getEdges()); //O(n^2)
excludeState.setPoint(x, y, double.PositiveInfinity); //make chosen point infinity
reduceMatrix(excludeState); //O(n^2)
excludeState.setEdges(state.getEdges()); //initialize excludeStates edges
return(excludeState);
}
public void reduceMatrix(State currentState) //O(n^2)
{
double lowerBound = currentState.getLB();
for (int i = 0; i < currentState.getMap().GetLength(0); i++) // reduce rows
{ //O(n^2)
double minimum = double.PositiveInfinity; //find the lowest value in that row to reduce
for (int j = 0; j < currentState.getMap().GetLength(1); j++)
{
if (currentState.getPoint(i, j) < minimum)
{
minimum = currentState.getPoint(i, j);
}
}
if (minimum == 0) //if there is already a 0 in that row, don't waste time looping through it
{
continue;
}
if (minimum != double.PositiveInfinity)
{
for (int j = 0; j < currentState.getMap().GetLength(1); j++)
{ //reduce the other entire row by that value
double reducedPoint = currentState.getPoint(i, j) - minimum;
currentState.setPoint(i, j, reducedPoint);
}
lowerBound += minimum; //add that lowest value to the lowerBound
}
}
for (int j = 0; j < currentState.getMap().GetLength(1); j++) //reduce columns
{ //O(n^2)
double minimum = double.PositiveInfinity;
for (int i = 0; i < currentState.getMap().GetLength(0); i++)
{
if (currentState.getPoint(i, j) < minimum)
{
minimum = currentState.getPoint(i, j); //find the lowest value in the column
}
}
if (minimum == 0) //if there is already a 0 in that column, don't waste time looping through it
{
continue;
}
if (minimum != double.PositiveInfinity)
{
for (int i = 0; i < currentState.getMap().GetLength(0); i++)
{//reduce the entire column by that value
double lowerPoint = currentState.getPoint(i, j) - minimum;
currentState.setPoint(i, j, lowerPoint);
}
lowerBound += minimum; //add that minimum value to the lowerBound
}
}
currentState.setLB(lowerBound); //set the lowerbound
}
public int findExcludeMinusInclude(int x, int y, State state) //O(n^2)
{ //finds the exlude minus the include of a point in a matrix
State excludeState = makeExclude(x, y, state); //O(n^2)
reduceMatrix(excludeState); //O(n^2)
State includeState = makeInclude(x, y, state); //O(n^2)
reduceMatrix(includeState); //O(n^2)
int cost = Convert.ToInt32(excludeState.getLB() - includeState.getLB());
return(cost);
}
public State makeInclude(int x, int y, State state) //O(n^2)
{
State includeState = new State(copyMatrix(state.getMap()), state.getLB(), state.getEdges()); //O(n^2)
includeState.setPoint(y, x, double.PositiveInfinity); //set the "opposite point to infinity"
for (int j = 0; j < includeState.getMap().GetLength(1); j++) //set the row to infinity, O(n)
{
includeState.setPoint(x, j, double.PositiveInfinity);
}
for (int i = 0; i < includeState.getMap().GetLength(0); i++) //set the column to infinity, O(n)
{
includeState.setPoint(i, y, double.PositiveInfinity);
}
reduceMatrix(includeState); //O(n^2)
includeState.setEdges(state.getEdges()); //initialize includeState's dictionary of edges
return(includeState);
}
//O(n^2)
public void reduceMatrix(State currentState)
{
double lowerBound = currentState.getLB();
for (int i = 0; i < currentState.getMap().GetLength(0); i++) // reduce rows
{//O(n^2)
double minimum = double.PositiveInfinity; //find the lowest value in that row to reduce
for (int j = 0; j < currentState.getMap().GetLength(1); j++)
{
if (currentState.getPoint(i, j) < minimum)
minimum = currentState.getPoint(i, j);
}
if (minimum == 0) //if there is already a 0 in that row, don't waste time looping through it
continue;
if (minimum != double.PositiveInfinity)
{
for (int j = 0; j < currentState.getMap().GetLength(1); j++)
{ //reduce the other entire row by that value
double reducedPoint = currentState.getPoint(i, j) - minimum;
currentState.setPoint(i, j, reducedPoint);
}
lowerBound += minimum; //add that lowest value to the lowerBound
}
}
for (int j = 0; j < currentState.getMap().GetLength(1); j++) //reduce columns
{//O(n^2)
double minimum = double.PositiveInfinity;
for (int i = 0; i < currentState.getMap().GetLength(0); i++)
{
if (currentState.getPoint(i, j) < minimum)
minimum = currentState.getPoint(i, j); //find the lowest value in the column
}
if (minimum == 0) //if there is already a 0 in that column, don't waste time looping through it
continue;
if (minimum != double.PositiveInfinity)
{
for (int i = 0; i < currentState.getMap().GetLength(0); i++)
{//reduce the entire column by that value
double lowerPoint = currentState.getPoint(i, j) - minimum;
currentState.setPoint(i, j, lowerPoint);
}
lowerBound += minimum; //add that minimum value to the lowerBound
}
}
currentState.setLB(lowerBound); //set the lowerbound
}
//O(n^2)
public State makeInclude(int x, int y, State state)
{
State includeState = new State(copyMatrix(state.getMap()), state.getLB(), state.getEdges()); //O(n^2)
includeState.setPoint(y, x, double.PositiveInfinity); //set the "opposite point to infinity"
for (int j = 0; j < includeState.getMap().GetLength(1); j++) //set the row to infinity, O(n)
{
includeState.setPoint(x, j, double.PositiveInfinity);
}
for (int i = 0; i < includeState.getMap().GetLength(0); i++) //set the column to infinity, O(n)
{
includeState.setPoint(i, y, double.PositiveInfinity);
}
reduceMatrix(includeState); //O(n^2)
includeState.setEdges(state.getEdges()); //initialize includeState's dictionary of edges
return includeState;
}
//O(n^2)
public State makeExclude(int x, int y, State state)
{
State excludeState = new State(copyMatrix(state.getMap()), state.getLB(), state.getEdges()); //O(n^2)
excludeState.setPoint(x, y, double.PositiveInfinity); //make chosen point infinity
reduceMatrix(excludeState); //O(n^2)
excludeState.setEdges(state.getEdges()); //initialize excludeStates edges
return excludeState;
}
Stopwatch timer; //global timer
public void branchAndBoundSolve()
{
initialState = new State(new Double[Cities.Length, Cities.Length]);
timer = new Stopwatch();
timer.Start();
for (int i = 0; i < Cities.Length; i++) //O(n^2), initialize initialStates map
{
for (int x = 0; x < Cities.Length; x++)
{
initialState.setPoint(i, x, Cities[i].costToGetTo(Cities[x]));
if (initialState.getPoint(i, x) == 0)
{
initialState.setPoint(i, x, double.PositiveInfinity);
}
}
}
initialState.initializeEdges(); //initializeEdges initializes the state's dictionary
//with key 0 to n (# of cities), value -> -1
reduceMatrix(initialState); //reduce the matrix to find lower bound
queue = new IntervalHeap <State>(); //this is a global queue
BSSF = greedy(); //find initial best solution so far, O(n^4)
Console.WriteLine("BSSF: " + BSSF);
findGreatestDiff(initialState); //exclude minus include, O(n^3)
TimeSpan ts = timer.Elapsed;
bool terminatedEarly = false; //boolean to keep track if we stopped after 30 seconds
int maxStates = 0; //keeps track of the maximum amount of states in the queue at one point
int totalSeconds = 0;
while (queue.Count != 0) //O(2^n * n^3), because each time you expand a node, it expands it 2 times, exponentially
{ //where n is the number of cities
if (queue.Count > maxStates) //if maxStates needs to be updated, update it
{
maxStates = queue.Count;
}
ts = timer.Elapsed;
State min = queue.DeleteMin();
if (totalSeconds < ts.Seconds)
{
totalSeconds = ts.Seconds;
Console.WriteLine("seconds: " + totalSeconds);
}
if (min.getLB() < BSSF) //if the min popped off the queue has a lowerbound less than
{
findGreatestDiff(min); //the BSSF, expand it, otherwise, prune it. -> O(n^3)
}
else
{//all of the lowerbounds are worse than the BSSF, break!
break;
}
}
if (!terminatedEarly)//if it solved the problem in less than 30 seconds
{
int city = 0;
for (int i = 0; i < bestState.getEdges().Count; i++) //O(n)
{
if (i == 0) //outputting a map into the Route list
{
Route.Add(Cities[i]);
city = bestState.getEdge(i);
}
else
{
Route.Add(Cities[city]);
city = bestState.getEdge(city);
}
}
bssf = new TSPSolution(Route);
// update the cost of the tour.
Program.MainForm.tbCostOfTour.Text = " " + bssf.costOfRoute();
Program.MainForm.tbElapsedTime.Text = ts.TotalSeconds.ToString();
// do a refresh.
Program.MainForm.Invalidate();
}
}
