public override void Evolve()
{
// calc SGM
var sgm = BuildFitnessSgm(this.P);
// Evolve the two subpopulation
var intensificationPop = this.Intensification(this.P, this.P_e, sgm);
var diversityPop = this.Diversity(this.P, this.P.Length - intensificationPop.Length, sgm);
// Combine the two populations
Genotype[] newPop = new Genotype[this.P.Length];
for (int i = 0; i < intensificationPop.Length; i++)
{
newPop[i] = intensificationPop[i];
}
for (int i = 0; i < diversityPop.Length; i++)
{
newPop[i + intensificationPop.Length] = diversityPop[i];
}
// Sort and go to the next generation
newPop = newPop.OrderBy(c => c.Cost).ToArray();
if (this.P[0].Cost < newPop[0].Cost)
{
newPop[0] = this.P[0];
}
this.P = newPop;
}
public virtual void Evolve() {
// calc SGM
var sgm = BuildSgm(this.P);
// Evolve the two subpopulation
var intensificationPop = this.Intensification(this.P, this.P_e, sgm);
var diversityPop = this.Diversity(this.P, this.P.Length - intensificationPop.Length, sgm);
// Combine the two populations
Genotype[] newPop = new Genotype[this.P.Length];
try {
Array.Copy(intensificationPop, 0, newPop, 0, intensificationPop.Length);
}
catch (Exception e) {
Console.Error.Write(e);
System.Environment.Exit(1);
}
try {
Array.Copy(diversityPop, 0, newPop, intensificationPop.Length, diversityPop.Length);
}
catch (Exception e) {
Console.Error.Write(e);
System.Environment.Exit(1);
}
// Sort
newPop = newPop.OrderBy(c => c.Cost).ToArray();
this.P = newPop;
}
public Genotype[] GetElite(int elite, Genotype[] pop, double minDist) {
List<Genotype> elites = new List<Genotype>();
Genotype lastElite = null;
int pIndex = 0;
while (elites.Count < elite) {
// Get the first elite
if (elites.Count == 0) {
lastElite = pop[pIndex];
elites.Add(lastElite);
pIndex++;
continue;
}
// Get the rest of the elites
if (GeneticAlgorithm.GeneticAlgorithmFunctions.HammingDis(lastElite.Sequence, pop[pIndex].Sequence) >= minDist) {
lastElite = pop[pIndex];
elites.Add(lastElite);
}
pIndex++;
if (pIndex >= pop.Length) {
break;
}
}
return elites.ToArray();
}
/// <summary>
/// Intensification method according to Zhang et al. (2018) in Algorithm 3.
/// Some parts have been tweaked to adapt to ordered problem constraints
/// </summary>
/// <param name="pop"></param>
/// <param name="subPopSize"></param>
/// <returns></returns>
public override Genotype[] Intensification(Genotype[] pop, int subPopSize, double[,] sgm)
{
Random rand = new Random(Guid.NewGuid().GetHashCode());
//----------------------------------------------------------------------------------------------------------
// Step 1: Compute S_E and copy the best individuals into the next generation
//----------------------------------------------------------------------------------------------------------
Genotype[] subPop = GetElite(subPopSize, pop, M_d);
Genotype[] newPop = new Genotype[subPop.Length];
var sgm = BuildSgm(subPop);
var S_E = GetReferencePoint(sgm);
//----------------------------------------------------------------------------------------------------------
// Step 2: According to S_E, compute each vector of ppSGM M_P
//----------------------------------------------------------------------------------------------------------
// Get the control amplitude
double CA = CalcControlAmplitude(pop);
var M_P = BuildPerturbationMatrix(sgm, CA, false);
//----------------------------------------------------------------------------------------------------------
// Step 3: Breed temporary individuals by using pp=SGM and M_P and Alg 1. Similar to Alg 3, execute
// crossover between temporary individuals and intensification subpopulation after updating.
//----------------------------------------------------------------------------------------------------------
// Calc probabilty of mutation
double p_m = 1 / (double)this.N;
// Create the temporary individuals that reflect the subpopulation
int[][] temporaryIndividuals = new int[pop.Length][];
Parallel.For(0, subPop.Length, ind => {
temporaryIndividuals[ind] = this.NewTemporaryIndividual(M_P, this.N);
});
// Crossover and mutation
Parallel.For(0, subPop.Length, i => {
if (i == 0)
{
newPop[i] = subPop[i];
}
// var candidate = temporaryIndividuals[i];
var candidate = pop[GeneticAlgorithmFunctions.Select(pop.Length)].Sequence;
var genotype = subPop[i];
var seq = GeneticAlgorithm.GeneticAlgorithmFunctions.Crossover(candidate, genotype.Sequence);
seq = GeneticAlgorithm.GeneticAlgorithmFunctions.Mutate(seq, p_m);
var cost = Problem.CalcCostRoute(seq);
newPop[i] = new Genotype(seq, cost);
});
// Sort and return
newPop = subPop.OrderBy(c => c.Cost).ToArray();
return(newPop);
}
/// <summary>
/// Diversity method according to Zhang et al. (2018) in Algorithm 3.
/// Some parts have been tweaked to adapt to ordered problem constraints
/// </summary>
/// <param name="pop"></param>
public override Genotype[] Diversity(Genotype[] pop, int subPopSize, double[,] sgm)
{
Random rand = new Random(Guid.NewGuid().GetHashCode());
Genotype[] newPop = new Genotype[pop.Length];
// Get the control amplitude
double CA = CalcControlAmplitude(pop);
//----------------------------------------------------------------------------------------------------------
// Step 1: According to S_G, compute each vector of np_SGM M_N from Alg. 3 (Zhang et al. 2018)
//----------------------------------------------------------------------------------------------------------
// var sgm = BuildSgm(pop);
var M_N = BuildPerturbationMatrix(sgm, CA, true);
// Create the temporary individuals that reflect the subpopulation
int[][] temporaryIndividuals = new int[pop.Length][];
Parallel.For(0, newPop.Length, ind => {
temporaryIndividuals[ind] = this.NewTemporaryIndividual(M_N, this.N);
});
// Calculate the mutation probability
double p_m = (1.0 + this.M_s * CA) / (double)N;
//----------------------------------------------------------------------------------------------------------
// Step 2: Breed temporary individuals by using np-SGM M_N and Algorithm 1, and execute crossover
//----------------------------------------------------------------------------------------------------------
Parallel.For(0, newPop.Length, ind => {
int[] O = new int[this.N];
for (int i = 0; i < O.Length; i++)
{
O[i] = rand.NextDouble() <= 0.5 ? temporaryIndividuals[ind][i] : pop[ind].Sequence[i];
}
// Step 3: Execute mutation according to mutation probability pm in Eq. (17) and ms is multiplier factor
O = GeneticAlgorithm.GeneticAlgorithmFunctions.Mutate(O, p_m);
int cost = Problem.CalcCostRoute(O);
newPop[ind] = new Genotype(O, cost);
});
// Sort and return
newPop = newPop.OrderBy(c => c.Cost).ToArray();
Genotype[] returnPop = new Genotype[subPopSize];
Array.Copy(newPop, 0, returnPop, 0, returnPop.Length);
return(returnPop);
}
public Genotype[] InitialisePopulation(Instance instance, int p) {
Random rand = new Random(Guid.NewGuid().GetHashCode());
Genotype[] pop = new Genotype[p];
for (int i = 0; i < p; i++) {
// Build a sequence
int[] sequence = new int[this.Problem.Nodes.Length];
for (int j = 1; j <= sequence.Length; j++) {
sequence[j - 1] = j;
}
// Shuffle it and get the cost
sequence = sequence.OrderBy(x => rand.Next()).ToArray();
int cost = instance.CalcCostRoute(sequence);
Genotype genotype = new Genotype(sequence, cost);
pop[i] = genotype;
}
return pop;
}
