public static EvaluatedConfiguration EvaluateConfiguration(this Instance instance, long configuration)
{
var weight = instance.GetWeight(configuration);
var res = new EvaluatedConfiguration(instance, configuration, weight);
return(res);
}
private EvaluatedConfiguration GetRandomConfiguration(Instance instance, EvaluatedConfiguration currentConfiguration)
{
var variableIndex = rand.Next(instance.VariableCount);
var variableBitArray = 1L << variableIndex;
var newConfiguration = currentConfiguration.Configuration ^ variableBitArray;
var newWeight = instance.GetWeight(newConfiguration);
return(new EvaluatedConfiguration(instance, newConfiguration, newWeight));
}
public EvaluatedConfiguration Solve(Instance instance)
{
var bestConfiguration = new EvaluatedConfiguration(instance, 0, 0);
var max = 1L << instance.VariableCount;
for (var configuation = 0L; configuation < max; configuation++)
{
var weight = instance.GetWeight(configuation);
if (weight > bestConfiguration.Weight)
{
bestConfiguration.Configuration = configuation;
bestConfiguration.Weight = weight;
}
}
return(bestConfiguration);
}
public EvaluatedConfiguration Solve(Instance instance)
{
var currentConfiguration = new EvaluatedConfiguration(instance, 0, 0);
var bestConfiguration = currentConfiguration;
for (var temperature = initTemperature; IsFrozen(temperature); temperature *= coolingCoeficient)
{
currentConfiguration = bestConfiguration; // it is good to go back to best result sometimes
for (var innerCycle = 0; Equilibrium(instance, innerCycle); ++innerCycle)
{
currentConfiguration = GetNextConfiguration(instance, temperature, currentConfiguration);
OnNewConfiguration(currentConfiguration);
if (currentConfiguration.Weight > bestConfiguration.Weight)
{
bestConfiguration = currentConfiguration;
}
}
}
OnNewConfiguration(bestConfiguration);
return(bestConfiguration);
}
protected virtual void OnNewConfiguration(EvaluatedConfiguration e)
{
NewConfiguration?.Invoke(this, e);
}
private EvaluatedConfiguration GetNextConfiguration(Instance instance, double temperature, EvaluatedConfiguration currentConfiguration)
{
// get random state (only fitting in knapsack)
var newConfiguration = GetRandomConfiguration(instance, currentConfiguration);
// when new state is better
if (newConfiguration.Weight > currentConfiguration.Weight)
{
return(newConfiguration);
}
else // when new state is worse
{
var random = rand.NextDouble();
var delta = currentConfiguration.Weight - newConfiguration.Weight;
var useWorse = random < Math.Exp(-delta / temperature);
return(useWorse ? newConfiguration : currentConfiguration);
}
}
