projet_optim_m2/src/halton.cpp

#include "halton.h"
#include <cassert>


// compute \phi_p^\pi(i)
double phi(int p, permutation pi, int i) {
  double r = 0., pl = 1./p;
  while(i) {
    r += (double)pi[i%p]*pl;
    pl /= p;
    i /= p;
  }
  return r;
}

halton::halton(int dim, int *p) : dim(dim), p(p) {
  assert(dim > 0);
  for(int i = 0; i < dim; i++)
    pi.push_back(permutation(p[i]));
}

permutation& halton::get_pi(int i) {
  assert(0 <= i && i < dim);
  return pi[i];
}

void halton::compute(int i, double* res) {
  for(int d = 0; d < dim; d++) {
    res[d] = phi(p[d], pi[d], i);
  }
}