/* DESCRIPTION:
* This method implements the A Algorithm.
* Uses direct distance to the final city as a heuristic.
* At each step finds the best next city to explore from citiesToExplore.
* Finds the cities connected to it and examines them.
* If the connected city is already found, then it examines is the new path to
* it shorter than the already known one. If it is, than it renew the information
* about the city in foundCities and citiesToExplore.
* If the city has not been found yet, then it add it to citiesToExplore and
* foundCities.
* When all cities have been explored it finds the minimal path using the idea
* that if the city B preceds the destination city A in the minimum path,
* then the minimum path also includes the minimum path from the start city
* to B. Thus, it goes from city to city in the reverse order and adds them
* to the minimum path.
*/
public List <City> FindOptimalPath()
{
City nextCity; // Next city to explore
CityInfo nextCityInfo; // Next city information
List <City> nextCityConnections; // Connections of the nextCity
CityInfo nextConnectedCityInfo; // Information about the currently examined city connected to nextCity
CityInfo nextConnectedCityOldInfo; // Old information about the currently examined city
Coordinates tempStartPoint, tempEndPoint; // Help variables. Store points on the map.
City tempCity, tempPrevCity; // Help variables. Store consecutive sities in the optimal path
CityInfo tempCityInfo; // Help variable. Stores a city's info
LogManager logManager = new LogManager(textBoxLog); // Log manager
bool finalCityIsFound = false; // Flag that we found the final city
double distanceToFinal = -1; // Length of the found path to the final city
// Print log - algorithm start
logManager.Clear();
logManager.PrintStartAlg(StartCity, FinalCity, AlgHeuristic);
// Start with the start city:))
nextCity = StartCity;
nextCityInfo = new CityInfo(StartCity, null, FinalCity,
GetCityCoordinates(StartCity), null, GetCityCoordinates(FinalCity),
0, AlgHeuristic);
// Initialize
foundCities = new Dictionary <City, CityInfo>();
citiesToExplore = new Dictionary <City, CityInfo>();
// Add the start city
foundCities.Add(nextCity, nextCityInfo);
citiesToExplore.Add(nextCity, nextCityInfo);
// While we have cities to explore
while (citiesToExplore.Count != 0)
{
// Print log
logManager.PrintFoundExploredCities();
// Clean the layout
graphManager.UnmarkAllCities(graphLayout);
graphManager.UnmarkAllEdges(graphLayout);
// Highlighting
graphManager.MarkAllFoundCities(new List <City>(foundCities.Keys), graphLayout);
graphManager.MarkAllCitiesToExplore(new List <City>(citiesToExplore.Keys), graphLayout);
graphManager.MarkStartCity(StartCity, graphLayout);
graphManager.MarkFinalCity(FinalCity, graphLayout);
// Wait
Wait();
// Find the next best city among citiesToExplore
nextCity = FindBestCity(citiesToExplore);
// Get its info
citiesToExplore.TryGetValue(nextCity, out nextCityInfo);
// Stop if all the estimates are greater than the found path length
if (finalCityIsFound)
{
if (nextCityInfo.PathDistance >= distanceToFinal)
{
break;
}
}
// Get the nextCity connections
citiesConnecitons.connections.TryGetValue(nextCity, out nextCityConnections);
// Print log - next city to explore
logManager.PrintBestCity(nextCity, nextCityInfo);
// Highlighting - next city to explore
graphManager.UnmarkAllCities(graphLayout);
graphManager.UnmarkAllEdges(graphLayout);
graphManager.MarkBestCity(nextCity, graphLayout);
// Print log - city connections
logManager.PrintCityConnections(nextCityConnections);
// Highlighting - city connections
graphManager.MarkEdges(nextCity, nextCityConnections, graphLayout);
graphManager.MarkAllCheckedCities(nextCityConnections, graphLayout);
Wait();
// Examine all the connections of the nextCity
foreach (City nextConnectedCity in nextCityConnections)
{
// Get the examined city location and the nextCity location
citiesLocations.locations.TryGetValue(nextCity, out tempStartPoint);
citiesLocations.locations.TryGetValue(nextConnectedCity, out tempEndPoint);
// Create information about the currently examined city
if (AlgHeuristic == Heuristic.Distance)
{
nextConnectedCityInfo = new CityInfo(nextConnectedCity, nextCity, FinalCity,
tempEndPoint, tempStartPoint, GetCityCoordinates(FinalCity),
FindDistance(tempStartPoint, tempEndPoint) + nextCityInfo.FromStart,
AlgHeuristic);
}
// If we use number of hops as a heuristic
else
{
nextConnectedCityInfo = new CityInfo(nextConnectedCity, nextCity, FinalCity,
tempEndPoint, tempStartPoint, GetCityCoordinates(FinalCity),
1 + nextCityInfo.FromStart, AlgHeuristic);
}
// If the examined city has already been found.
// If the current path is better, then update the city's info
if (foundCities.ContainsKey(nextConnectedCity))
{
// Get the city's old info from foundCities
foundCities.TryGetValue(nextConnectedCity, out nextConnectedCityOldInfo);
// Compare its old path distance to the new path distance
if (nextConnectedCityInfo.PathDistance <
nextConnectedCityOldInfo.PathDistance)
{
// Print log - updated city
logManager.PrintUpdatedCity(nextConnectedCity, nextConnectedCityInfo,
nextConnectedCityOldInfo);
// Highlighting - updated city
graphManager.MarkUpdatedCity(nextConnectedCity, graphLayout);
// Update the info if the new path is shorter
nextConnectedCityOldInfo.PrevCity = nextConnectedCityInfo.PrevCity;
nextConnectedCityOldInfo.FromStart = nextConnectedCityInfo.FromStart;
// If we updated the final city (found a better path)
if (nextConnectedCity.Equals(FinalCity))
{
distanceToFinal = nextConnectedCityInfo.FromStart;
}
}
else
{
// Print log - rejected city
logManager.PrintRejectedCity(nextConnectedCity, nextConnectedCityInfo,
nextConnectedCityOldInfo);
// Highlighting - rejected city
graphManager.MarkRejectedCity(nextConnectedCity, graphLayout);
}
}
// If we have not found this city so far.
// Add it to foundCities and citiesToExplore.
else
{
// Add the city to foundCities and citiesToExplore.
foundCities.Add(nextConnectedCity, nextConnectedCityInfo);
citiesToExplore.Add(nextConnectedCity, nextConnectedCityInfo);
// Print log - added city
logManager.PrintAddedCity(nextConnectedCity, nextConnectedCityInfo);
// Highlighting - added city
graphManager.MarkAddedCity(nextConnectedCity, graphLayout);
// Check wether we added the desired final city
if (!finalCityIsFound)
{
if (nextConnectedCity.Equals(FinalCity))
{
finalCityIsFound = true;
distanceToFinal = nextConnectedCityInfo.FromStart;
}
}
}
}
// Wait
Wait();
// Mark nextCity as explored.
// Remove it from citiesToExplore
nextCityInfo.IsExplored = true;
citiesToExplore.Remove(nextCity);
}
// If we were able to reach the destination,
// then construct the optimal path.
if (foundCities.ContainsKey(FinalCity))
{
// Start with the end city
tempCity = FinalCity;
// Get the end city info
foundCities.TryGetValue(tempCity, out tempCityInfo);
// Initialize
List <City> optimalPath = new List <City>();
// Add the end city to the optimal path
optimalPath.Add(tempCity);
// Set the city that preceds the end city in the optimal path
tempPrevCity = tempCityInfo.PrevCity;
// While we have not reached the start city
while (tempPrevCity != null)
{
// Add the city that preceds the current city in the optimal path
tempCity = tempPrevCity;
optimalPath.Add(tempCity);
// Move to the previous city in the path in order to
// add it in the next loop iteration.
foundCities.TryGetValue(tempCity, out tempCityInfo);
tempPrevCity = tempCityInfo.PrevCity;
}
// Reverse the list
ReverseListOrder(ref optimalPath);
// Print log - optimal path
logManager.PrintPath(optimalPath,
Algorithm.CalculateTotalPath(optimalPath, citiesLocations));
// Highlighting - optimal path
graphManager.UnmarkAllCities(graphLayout);
graphManager.UnmarkAllEdges(graphLayout);
graphManager.MarkPath(optimalPath, graphLayout);
// Print log - end of the algorithm
logManager.PrintEndAlg(true);
return(optimalPath);
}
// Output an error if the destination could not be reached.
else
{
// Highlighting
graphManager.UnmarkAllCities(graphLayout);
graphManager.UnmarkAllEdges(graphLayout);
graphManager.MarkStartCity(StartCity, graphLayout);
graphManager.MarkFinalCity(FinalCity, graphLayout);
// Print log - end of the algorithm
logManager.PrintEndAlg(false);
// Output an error that the path was not found
MessageBox.Show("Cannot find a path between the chosen cities.",
"Path Finder", MessageBoxButton.OK, MessageBoxImage.Warning);
return(null);
}
}
/// <summary>
/// Stop the algorithm execution and kill the algorithm thread
/// </summary>
public void StopAlgorithm()
{
if (algThread != null)
{
algThread.Abort();
}
if (algorithm != null)
{
algorithm.IsRunning = false;
algorithm = null;
}
}
public LogicManager(MainWindow _window)
{
graphToVisualize = null;
citiesLocations = null;
citiesConnections = null;
defaultCitiesLocations = new CitiesLocations();
defaultCitiesConnections = new CitiesConnections();
algCitiesLocations = new CitiesLocations();
startCity = null;
finalCity = null;
algSpeed = Alg_Speed.Fast;
algHeuristic = Heuristic.Distance;
resources = _window.Resources;
window = _window;
graphManager = new GraphManager(window);
algorithm = null;
algThread = null;
IsRunningAlg = false;
}
/// <summary>
/// Start A-star algorithm in a separate thread
/// </summary>
/// <param name="graphLayout"></param>
/// <param name="richTextBoxLog"></param>
/// <param name="window"></param>
public void StartAlgorithm(ref GraphLayoutCity graphLayout, ref TextBox richTextBoxLog,
MainWindow window)
{
// If already running
if (IsRunningAlg)
{
algorithm.WaitMutex.WaitOne();
algorithm.CanContinue = true;
algorithm.WaitMutex.ReleaseMutex();
}
// If not, then start a new thread
else
{
algorithm = new Algorithm(citiesLocations, citiesConnections,
startCity.City, finalCity.City, algSpeed, algHeuristic,
ref graphLayout, ref richTextBoxLog, resources, graphManager);
// Set window and create a mutex
algorithm.Window = window;
algorithm.WaitMutex = new Mutex();
// Null the start and end cities
startCity = null;
finalCity = null;
// Create and start the thread
algThread = new Thread(new ThreadStart(algorithm.RunAlgThread));
algThread.SetApartmentState(ApartmentState.STA);
algThread.Start();
// Allow the algorithm to continue
algorithm.WaitMutex.WaitOne();
algorithm.CanContinue = true;
algorithm.WaitMutex.ReleaseMutex();
}
}
