// generate batch of N samples from a target distribution p(x)
// using sampling-importance-rejection sampling w/ one resampling stage
Matrix rvSIRBatch(const int& N, const double& PDFscale)
{
int j=0, k=0, m=0;
Matrix Qsamples(1,N);
Matrix w(1,N);
Matrix wCDF(1,N);
Matrix rand(1,N);
Matrix x(1,N);
// sample from q(x) and calculate weights (and create random array for later)
for(int i=0;i<N;i++)
{
Qsamples[0][i] = rvStdUniform(-1,1)*PDFscale; // [-1,1] to handle all PDFs
//w[0][i] = p_x(Qsamples[0][i])/Qsamples[0][i];
// line below works, line above doesn't;
w[0][i] = p_x(Qsamples[0][i])/PDFscale;
rand[0][i] = rvStdUniform(0,1);
}
// normalize weights
w = w/w.sum();
// create CDF of weights
wCDF[0][0] = w[0][0];
for(int j=1;j<N;j++)
wCDF[0][j] = wCDF[0][j-1] + w[0][j];
//make copies as many times as numbers occur in CDF
for(k = 0; k < N; ++k)
{
m = 0;
while(wCDF[0][m] < rand[0][k])
{
++m;
}
x[0][k] = Qsamples[0][m];
}
// reset weights to uniform values
double wUniform = 1./N;
w.fill(wUniform);
return x;
}
// generate one sample from a target distribution p(x) using rejection sampling
double rvRejectionSample(const double& M, const double& PDFscale)
{
double x, u, target, rejectRatio;
// note: PDFscale scales the related density g(x) to ensure
// it's larger than the distribution we want to sample;
// otherwise we'll just end up sampling g(x)
// note: machine learning book says to use u < p(x)/Mg(x)
// as the acceptance criteria, but actually uses u < p(x)
// also, book says to sample from g(x) Gaussian (for Gaussian desired density)
// but actually uses uniform density
// the following code is "correct" but doesn't seem
// to match desired density as well as book's method
// to use book's method, comment out all *^ lines
// and comment in all ** lines
// generate initial sample
x = rvGaussian(0,1)*PDFscale; // related density, here Gaussian
// can also just choose a constant value
// larger than the max of the target distribution
// *^
//x = rvStdUniform(0,1)*PDFscale; // **
u = rvStdUniform(0,1)*M; // enveloping uniform distribution
//rejectRatio = p_x(x)/u; // threshold to accept/reject samples *^
// generate sample x until it falls within the target distribution
//while( u >= rejectRatio) // *^
while( u >= p_x(x) ) // **
{
x = rvGaussian(0,1)*PDFscale; // *^
//x = rvStdUniform(0,1)*PDFscale; // **
u = rvStdUniform(0,1)*M;
//rejectRatio = p_x(x)/u; // *^
}
return x;
}
void GeneticAlgorithm::Crossover(std::vector<char***> &population, float probability, float infeasibilitiesWeight,
float didacticDissatisfactionWeight, float organizationalDissatisfactionWeight)
{
int num_pairs = population.size() / 2;
int size = population.size();
std::vector<bool> free_pairs(size, true);
// Losowanie par.
for(int i = 0; i < num_pairs; ++i)
{
int x = rand() % size;
int y = rand() % size;
while(!free_pairs[x])
{
x++;
if(x == size)
x = 0;
}
free_pairs[x] = false;
while(!free_pairs[y])
{
y++;
if(y == size)
y = 0;
}
free_pairs[y] = false;
// Krzy¿uj.
if(rand() % 100 < probability * 100)
{
std::vector<std::pair<int, float>> x_fitness;
for(int teacher = 0; teacher < teachers_count; ++teacher)
{
float xf = CalculateLocalFitnessFunction(population.data(), x, teacher,
didacticDissatisfactionWeight, organizationalDissatisfactionWeight);
std::pair<int, float> p_x(teacher, xf);
x_fitness.push_back(p_x);
}
std::sort(x_fitness.begin(), x_fitness.end(),
[] (std::pair<int, float> &_x, std::pair<int, float> &_y) -> bool { return _x.second < _y.second; } );
int k = teachers_count / 2;
// TODO: wybieraæ k na podstawie œredniej.
char ***timetable1 = new char**[teachers_count];
char ***timetable2 = new char**[teachers_count];
for(int t = 0; t < teachers_count; ++t)
{
if(t < k)
{
timetable1[x_fitness[t].first] = population[x][x_fitness[t].first];
timetable2[x_fitness[t].first] = population[y][x_fitness[t].first];
}
else
{
timetable1[x_fitness[t].first] = population[y][x_fitness[t].first];
timetable2[x_fitness[t].first] = population[x][x_fitness[t].first];
}
}
delete [] population[x];
delete [] population[y];
population[x] = timetable1;
population[y] = timetable2;
}
}
}