public TravellingSalesmanAlgorithm(Location startLocation, Location[] destinations, int populationCount)
{
if (startLocation == null)
throw new ArgumentNullException("startLocation");
if (destinations == null)
throw new ArgumentNullException("destinations");
if (populationCount < 2)
throw new ArgumentOutOfRangeException("populationCount");
if (populationCount % 2 != 0)
throw new ArgumentException("The populationCount parameter must be an even value.", "populationCount");
_startLocation = startLocation;
destinations = (Location[])destinations.Clone();
foreach(var destination in destinations)
if (destination == null)
throw new ArgumentException("The destinations array can't contain null values.", "destinations");
// This commented method uses a search of the kind "look for the nearest non visited location".
// This is rarely the shortest path, yet it is already a "somewhat good" path.
destinations = _GetFakeShortest(destinations);
_populationWithDistances = new KeyValuePair<Location[], double>[populationCount];
// Create initial population.
for(int solutionIndex=0; solutionIndex<populationCount; solutionIndex++)
{
var newPossibleDestinations = (Location[])destinations.Clone();
// Try commenting the next 2 lines of code while keeping the _GetFakeShortest active.
// If you avoid the algorithm from running and press reset, you will see that it always
// start with a path that seems "good" but is not the best.
//for(int randomIndex=0; randomIndex<newPossibleDestinations.Length; randomIndex++)
//RandomProvider.FullyRandomizeLocations(newPossibleDestinations);
var distance = Location.GetTotalDistance(startLocation, newPossibleDestinations);
var pair = new KeyValuePair<Location[], double>(newPossibleDestinations, distance);
_populationWithDistances[solutionIndex] = pair;
}
Array.Sort(_populationWithDistances, _sortDelegate);
}
private Location[] _Reproduce(Location[] parent)
{
var result = (Location[])parent.Clone();
if (!MustDoCrossovers)
{
// When we are not using cross-overs, we always apply mutations.
RandomProvider.MutateRandomLocations(result);
return result;
}
// if you want, you can ignore the next three lines of code and the next
// if, keeping the call to RandomProvider.MutateRandomLocations(result); always
// invoked and without crossovers. Doing that you will not promove evolution through
// "sexual reproduction", yet the good result will probably be found.
int otherIndex = RandomProvider.GetRandomValue(_populationWithDistances.Length/2);
var other = _populationWithDistances[otherIndex].Key;
RandomProvider._CrossOver(result, other, MustMutateFailedCrossovers);
if (!MustMutateFailedCrossovers)
if (RandomProvider.GetRandomValue(10) == 0)
RandomProvider.MutateRandomLocations(result);
return result;
}
