public static void Subsample <T>(IList <T> items, int count)
{
if (items.Count <= count)
{
return;
}
for (int i = 0; i < count; ++i)
{
int swapIndex = Random.Int(i, items.Count);
T tmp = items[i];
items[i] = items[swapIndex];
items[swapIndex] = tmp;
}
}
public T Run(T startSolution, Func <T, double, T> mutationFunction, Func <T, double> objectiveFunction)
{
if (startSolution == null)
{
throw new ArgumentNullException("startSolution");
}
if (mutationFunction == null)
{
throw new ArgumentNullException("mutationFunction");
}
if (objectiveFunction == null)
{
throw new ArgumentNullException("objectiveFunction");
}
T bestSolution = startSolution;
double minObjective = objectiveFunction(bestSolution);
int lastUpdateIteration = 0;
int currentIteration = 0;
int iterationsFromLastReannealing = 0;
double prevObjective = minObjective;
T prevSolution = bestSolution;
while (currentIteration < this.MaxIterations && currentIteration - lastUpdateIteration < this.MaxStallingIterations)
{
double temperature = CalcTemperature(iterationsFromLastReannealing);
T currentSolution = mutationFunction(prevSolution, temperature);
double currentObjective = objectiveFunction(currentSolution);
double acceptanceProb = CalcAcceptanceProbability(prevObjective, currentObjective, temperature);
if (Random.Double() < acceptanceProb)
{
prevObjective = currentObjective;
prevSolution = currentSolution;
}
if (currentObjective < minObjective)
{
lastUpdateIteration = currentIteration;
minObjective = currentObjective;
bestSolution = currentSolution;
DebugConfiguration.WriteDebugText("Best solution update: {0:0.000}", minObjective);
}
++currentIteration;
if (currentIteration % this.reportRate == 0)
{
DebugConfiguration.WriteDebugText("Iteration {0}", currentIteration);
if (this.AnnealingProgress != null)
{
this.AnnealingProgress(this, new SimulatedAnnealingProgressEventArgs <T>(currentSolution, bestSolution));
}
}
if (iterationsFromLastReannealing >= this.ReannealingInterval)
{
iterationsFromLastReannealing = 0;
prevSolution = bestSolution;
DebugConfiguration.WriteDebugText("Reannealing");
}
else
{
++iterationsFromLastReannealing;
}
}
return(bestSolution);
}
