/// <summary>
/// Progresses the optimization by evolving the current population.
/// </summary>
/// <returns>The number of generations thus far.</returns>
public int NewGeneration()
{
if (population == null)
{
throw new InvalidOperationException("Cannot generate a next" +
" generation without prior call to StartEvolution!");
}
List <Individual> newPopulation = new List <Individual>();
generationCount++;
WeightedSampler <Individual> sampler = new WeightedSampler <Individual>();
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
// Check the fitness values of the current generation.
foreach (Individual individual in population)
{
if (individual.Fitness < 0)
{
throw new ArgumentOutOfRangeException("solutionFitness function",
"Negative fitness values are not allowed! Use 0 fitness " +
"for solutions that should not reproduce.");
}
if (individual.Fitness > bestSolution.Fitness)
{
bestSolution = new Individual(individual.DNA, individual.Fitness);
}
maxFitness = Math.Max(individual.Fitness, maxFitness);
minFitness = Math.Min(individual.Fitness, minFitness);
}
double averageHealth = 0;
double averageBitsSet = 0;
double averageAge = 0;
int acceptedTotal = 0;
int acceptedWorse = 0;
int purgedIndividuals = 0;
// Sort the population by fitness.
population = population.OrderBy(ind => ind.Fitness).ToArray();
int index = 0;
foreach (Individual individual in population)
{
index++;
/// Max and min fitness might have changed, so we need to
/// normalize the fitnesses again.
individual.normalizedFitness = normalizeFitness(individual.Fitness);
averageHealth += individual.normalizedFitness;
averageBitsSet += SetBits(individual.DNA);
// Survival of the fittest (population was ordered by fitness above)
if (index < 0.5 * populationSize)
{
// Could be slightly more concise, I know.
purgedIndividuals++;
continue;
}
/// This seems to have a good effect on convergence speed.
/// By only allowing solutions that survived a round of culling
/// to procreate, the solution quality is kept high.
if (individual.Age >= 1)
{
sampler.AddEntry(individual, individual.normalizedFitness);
}
averageAge += individual.Age;
individual.Age++;
// Simulated annealing
Individual temp = individual;
Individual mutation = spawnIndividual(mutateDNA(individual.DNA));
mutation.Age = individual.Age - 1; // TODO: Investigate.
if (acceptNewState(individual, mutation))
{
acceptedTotal++;
if (mutation.Fitness < individual.Fitness)
{
acceptedWorse++;
}
temp = mutation;
}
newPopulation.Add(temp);
}
/*if (purgedIndividuals == 0)
* minFitness = minCurrentFitness;*/
stopwatch.Stop();
Console.Write("Evaluation time for " + generationCount + " : ");
Console.WriteLine(stopwatch.ElapsedMilliseconds + " ms");
Console.WriteLine("Temperature: " + temperature);
Console.WriteLine("Average health: " + averageHealth / populationSize);
Console.WriteLine("Average bits set: " + averageBitsSet / populationSize);
Console.WriteLine("Average age: " + averageAge / populationSize);
Console.WriteLine("Accepted new states (all/worse): " + acceptedTotal + "/" + acceptedWorse);
//Console.WriteLine("Purged individuals: " + purgedIndividuals + "/" + populationSize);
Console.WriteLine("Sampler entries: " + sampler.EntryCount);
stopwatch.Restart();
if (!sampler.CanSample)
{
// This is actually a pretty serious problem.
population = createPopulation();
Console.WriteLine("Entire population was infertile (Generation " +
generationCount + ").");
//Debug.Fail("Population went extinct, not good...");
return(generationCount);
}
// Breed population and apply random mutations.
int dnaResets = 0;
// Replace purged individuals
for (int i = 0; i < purgedIndividuals; i++)
{
BitArray parent1 = sampler.RandomSample().DNA;
BitArray parent2 = sampler.RandomSample().DNA;
BitArray newDNA = combineIndividualsDNA(parent1, parent2);
newPopulation.Add(spawnIndividual(newDNA));
}
population = newPopulation.ToArray();
// Yeah, I know, out of thin air.
temperature *= annealingFactor;
stopwatch.Stop();
Console.WriteLine("Best value so far: " + (1500 - bestSolution.Fitness));
Console.WriteLine("------------------");
Console.Out.Flush();
return(generationCount);
}
/// <summary>
/// Progresses the optimization by evolving the current population.
/// </summary>
/// <returns>The number of generations thus far.</returns>
public int NewGeneration()
{
if (population == null)
{
throw new InvalidOperationException("Cannot generate a next" +
" generation without prior call to InitializeEvolution!");
}
Individual[] newPopulation = new Individual[populationSize];
int newPopIndex = 0;
generationCount++;
WeightedSampler <Individual> sampler = new WeightedSampler <Individual>();
#if DEBUG
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
double averageHealth = 0;
double averageBitsSet = 0;
double averageAge = 0;
int acceptedTotal = 0;
int acceptedWorse = 0;
#endif
// Sort the population by fitness.
population = population.OrderBy(ind => ind.Fitness).ToArray();
int index = 0;
foreach (Individual individual in population)
{
index++;
#if DEBUG
averageHealth += 1500 - individual.Fitness;
averageBitsSet += SetBits(individual.DNA);
#endif
// Survival of the fittest (population was ordered by fitness above)
if (index < 0.5 * populationSize)
{
continue;
}
/// This seems to have a good effect on convergence speed.
/// By only allowing solutions that survived a round of culling
/// to procreate, the solution quality is kept high.
if (individual.Age >= 1)
{
sampler.AddEntry(individual, individual.Fitness);
}
#if DEBUG
averageAge += individual.Age;
#endif
individual.Age++;
newPopulation[newPopIndex] = individual;
newPopIndex++;
}
//for (int i = 0; i < newPopIndex; i++)
Parallel.For(0, newPopIndex, i =>
{
Individual temp = newPopulation[i];
Individual mutation = spawnIndividual(mutateDNA(temp.DNA));
// Lowering the age here would lead to faster convergence but would
// make the population go extinct several times.
mutation.Age = temp.Age;
// Mutations have a chance to be rejected based on the fitness loss
// relative to the non-mutated individual. See explanation above.
if (acceptNewState(temp, mutation))
{
#if DEBUG
// If you want to measure these for debugging purposes, remove the
// parallelization of this loop.
//acceptedTotal++;
//if (mutation.Fitness < temp.Fitness)
// acceptedWorse++;
#endif
temp = mutation;
}
newPopulation[i] = temp;
});
#if DEBUG
stopwatch.Stop();
//Console.Write("Evaluation time for " + generationCount + " : ");
//Console.WriteLine(stopwatch.ElapsedMilliseconds + " ms");
//Console.WriteLine("Average health: " + averageHealth / populationSize);
//Console.WriteLine("Average bits set: " + averageBitsSet / populationSize);
//Console.WriteLine("Average age: " + averageAge / populationSize);
//Console.WriteLine("Accepted new states (all/worse): " + acceptedTotal + "/" + acceptedWorse);
//Console.WriteLine("Sampler entries: " + sampler.EntryCount);
stopwatch.Restart();
#endif
if (!sampler.CanSample)
{
// This is actually a pretty serious problem.
population = createPopulation();
Console.WriteLine("Entire population was infertile (Generation " +
generationCount + ").");
//Debug.Fail("Population went extinct, not good...");
return(generationCount);
}
// Replace purged individuals
//for (int i = newPopIndex; i < populationSize; i++)
Parallel.For(newPopIndex, populationSize, i =>
{
BitArray parent1 = sampler.RandomSample().DNA;
BitArray parent2 = sampler.RandomSample().DNA;
BitArray newDNA = combineIndividualsDNA(parent1, parent2);
newPopulation[i] = spawnIndividual(newDNA);
});
population = newPopulation;
// Doing this at the end so the last generation has a use.
updateBestSolution();
#if DEBUG
stopwatch.Stop();
//Console.WriteLine("Best value so far: " + (1500 - bestSolution.Fitness));
//Console.WriteLine("------------------");
//Console.Out.Flush();
#endif
return(generationCount);
}
