public void CrowdingDistanceAssignment(Population_NSGA population)
{
int size = population.Population_size;
if (size == 0)
{
return;
}
if (size == 1)
{
population.Get(0).CrowdingDistance = Double.MaxValue;
return;
}
if (size == 2)
{
population.Get(0).CrowdingDistance = Double.MaxValue;
population.Get(1).CrowdingDistance = Double.MaxValue;
return;
}
Population_NSGA front = new Population_NSGA(size);
for (int i = 0; i < size; i++)
{
front.Add(population.Get(i));
}
for (int i = 0; i < size; i++)
{
front.Get(i).CrowdingDistance = 0.0;
}
double objetiveMaxn;
double objetiveMinn;
double distance;
//2 hàm mục tiêu
for (int i = 0; i < 2; i++)
{
// Sort the population by Obj n
front.Sort(new ObjectiveComparator(i));
objetiveMinn = front.Get(0).Objective[i];
objetiveMaxn = front.Get(front.Size() - 1).Objective[i];
//Set de crowding distance
front.Get(0).CrowdingDistance = double.PositiveInfinity;
front.Get(size - 1).CrowdingDistance = double.PositiveInfinity;
for (int j = 1; j < size - 1; j++)
{
distance = front.Get(j + 1).Objective[i] - front.Get(j - 1).Objective[i];
distance = distance / (objetiveMaxn - objetiveMinn);
distance += front.Get(j).CrowdingDistance;
front.Get(j).CrowdingDistance = distance;
}
}
}
/// <summary>
/// Runs the NSGA-II algorithm.
/// </summary>
/// <returns>a <code>SolutionSet</code> that is a set of non dominated solutions as a result of the algorithm execution</returns>
public Population_NSGA Execute()
{
int evaluations;
Population_NSGA population;
Population_NSGA offspringPopulation;
Population_NSGA union;
//Initialize the variables
evaluations = 0;
// Bước 1: Khởi tạo quần thể
// Create the initial solutionSet
population = new Population_NSGA(m_Population_size);
population = (Population_NSGA)Population.Clone();
// Danh gia ham muc tieu 1 cho quan the Pt
for (int i = 0; i < m_Population_size; i++)
{
Individual_NSGA individual = population.IndividualList[i];
individual.Objective[0] = CalculateMSE(individual, inputData);
}
// Danh gia ham muc tieu 2 cho quan the Pt
Diversity(population);
// Vòng lặp tiến hóa
while (evaluations < m_MaxEvaluations)
{
// Create the offSpring solutionSet
offspringPopulation = new Population_NSGA(m_Population_size); // Tập cá thể con
Individual_NSGA[] parents = new Individual_NSGA[2];
for (int i = 0; i < (m_Population_size / 2); i++) // N/2
{
if (evaluations < m_MaxEvaluations)
{
//Lấy 2 Cha parents
int sol1 = (int)(m_Random.NextDouble() * (m_Population_size - 1));
int sol2 = (int)(m_Random.NextDouble() * (m_Population_size - 1));
parents[0] = population.IndividualList[sol1];
parents[1] = population.IndividualList[sol2];
//
while (sol1 == sol2)
{
sol2 = (int)(m_Random.NextDouble() * (m_Population_size - 1));
parents[1] = population.IndividualList[sol2];
}
// Sử dụng SBX crossover tạo ra 2 thằng con
Individual_NSGA[] offSpring = SBXCrossover(parents);
//Dot bien
DoMutation(offSpring[0]);
DoMutation(offSpring[1]);
//Danh gia ham muc tieu 1 cho quan the moi Qt
offSpring[0].Objective[0] = CalculateMSE(offSpring[0], inputData);
offSpring[1].Objective[0] = CalculateMSE(offSpring[1], inputData);
// Đưa 2 con vào danh sách
offspringPopulation.Add(offSpring[0]);
offspringPopulation.Add(offSpring[1]);
evaluations += 2;
}
}
//Danh gia ham muc tieu 2 cho quan the moi Qt
Diversity(offspringPopulation);
// Create the solutionSet union of solutionSet and offSpring
union = ((Population_NSGA)population).Union(offspringPopulation);
// Ranking the union - Sxep ko troi - non-dominated sorting
Ranking ranking = new Ranking(union);
int remain = m_Population_size;
int index = 0;
Population_NSGA front = null;
population.Clear();
// Obtain the next front
front = ranking.GetSubfront(index);
// Đưa các Front vào quần thể mới, đến thằng cuối cùng
while ((remain > 0) && (remain >= front.Size()))
{
//Assign crowding distance to individuals
// Gắn khoang cach CrowdingDistance cho ca the
CrowdingDistanceAssignment(front);
//Add the individuals of this front
for (int k = 0; k < front.Size(); k++)
{
population.Add(front.Get(k));
}
//Decrement remain
remain = remain - front.Size();
//Obtain the next front
index++;
if (remain > 0)
{
front = ranking.GetSubfront(index);
}
}
// Remain is less than front(index).size, insert only the best one
if (remain > 0)
{ // front contains individuals to insert
CrowdingDistanceAssignment(front);
front.Sort(new CrowdingComparator());
for (int k = 0; k < remain; k++)
{
population.Add(front.Get(k));
}
remain = 0;
}
}
// Return the first non-dominated front
Ranking rank = new Ranking(population);
Population_NSGA result = rank.GetSubfront(0);
return(result);
}
public void Diversity(Population_NSGA population)
{
double objetiveMaxn;
double objetiveMinn;
double distance;
int N = population.Size();
if (N == 1)
{
population.IndividualList[0].Objective[1] = 1;
return;
}
//sắp xếp quần thể theo hàm mục tiêu từ bé đến lớn
population.Sort(new ObjectiveComparator(0));
//nếu quần thể chỉ có 2 cá thể thì ta lấy cả 2 chứ ko cần tính f2 nữa
//gán 1,2 để vẽ đồ thị.
if (N == 2)
{
population.IndividualList[0].Objective[1] = 1;
population.IndividualList[1].Objective[1] = 2;
return;
}
//nếu quần thể có từ 3 cá thể trở lên
objetiveMinn = population.IndividualList[0].Objective[0];
objetiveMaxn = population.IndividualList[N - 1].Objective[0];
population.IndividualList[0].Objective[1] = 0;
population.IndividualList[N - 1].Objective[1] = Double.MaxValue; //gán thế này cái cuối cùng sẽ luôn bị loại vì nhỏ hơn thì được ưu tiên
//if (indexF2 == 2)//cicle
//{
//tìm bán kính lớn nhât
double bkmax = 0;
for (int i = 0; i < N - 1; i++)
{
double temp = (population.IndividualList[i + 1].Objective[0] - population.IndividualList[i].Objective[0]);
if (bkmax < temp)
{
bkmax = temp;
}
}
double r = bkmax;
for (int i = 1; i < N - 1; i++)
{
distance = 0;
int dem = 0;
for (int j = 0; j < N; j++)
{
double dis = Math.Abs(population.IndividualList[i].Objective[0] - population.IndividualList[j].Objective[0]);
if (dis <= r)
{
distance += dis;
dem++;
}
}
if (dem <= 1)
{
distance /= (dem - 1);//vì tính cả chính nó nên phải trừ đi 1
}
population.IndividualList[i].Objective[1] = distance;
}
//}
//if (indexF2 == 0)//crowding
//{
// for (int j = 1; j < N - 1; j++)
// {
// distance = population.IndividualList[j + 1].Objective[0] - population.IndividualList[j - 1].Objective[0];
// distance = distance / (objetiveMaxn - objetiveMinn);
// population.IndividualList[j].Objective[1] = distance;
// }
//}
//if (indexF2 == 1)//distance
//{
// for (int i = 1; i < N - 1; i++)
// {
// distance = 0;
// for (int j = 0; j < N; j++)
// {
// distance += Math.Abs((population.IndividualList[i].Objective[0] - population.IndividualList[j].Objective[0]));
// }
// distance /= (N - 1);
// population.IndividualList[i].Objective[1] = distance;
// }
//}
}