/**
* Constructor
* @param Trial - pointer to trial wavefunction
* @param H - Hamiltonian of the system
* @param seed - seed for normal random number generator
* @param idum - seed for uniform random number generator
*/
Metropolis_Hastings::Metropolis_Hastings(Wavefunction* Trial, Hamiltonian* H,
long idum) {
this->Trial = Trial;
this->dim = Trial->get_dim();
this->numpart = Trial->get_numpart();
this->H = H;
this->idum = idum;
QFo = new QForce(Trial);
R_cur.set_size(numpart, dim);
R_tr.set_size(numpart, dim);
delta = 0.5;
interaction = Trial->get_int();
seed = (int) abs(idum);
RanNormalSetSeedZigVec(&seed, 200); // Initialize random number generator
exp_par_psi = zeros(2);
exp_par_psi2 = zeros(2);
par_psi = zeros(2);
}
/*******************************************************************
*
* NAME : run_importance_sampling(int cycles, int& accepted,
* double& energy, double& energy_sq)
*
* DESCRIPTION : Importance sampling
*/
void MC_Importance_Sampling::run_importance_sampling(int cycles, int& accepted, double& energy, double& energy_sq) {
int dum = (int) idum;
RanNormalSetSeedZigVec(&dum, 200);
// Special case for blocking. We need the rank when writing to file.
#if BLOCKING
int my_rank;
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
ostringstream filename;
filename << "Blocking/files/blocking_" << my_rank << ".dat";
ofstream blockfile(filename.str().c_str(), ios::out | ios::binary);
#endif
double delta_e, greens_function, R;
int n_particles = wf->getNParticles();
int dim = wf->getDim();
// Initiating variables
energy = 0;
energy_sq = 0;
accepted = 0;
delta_e = 0;
// Quantum Force.
mat q_force_old = zeros(n_particles, dim);
mat q_force_new = zeros(n_particles, dim);
// Initial position of the electrons
mat r_old = randn(n_particles, dim) * sqrt(dt);
mat r_new = r_old;
// Evalutating the Quantum Force and Wave Function in the inital position.
wf->set_r_new(r_old, 0);
wf->init_slater();
q_force_old = wf->q_force();
wf->accept_move();
// Monte Carlo cycles
for (int sample = 0; sample < (cycles + thermalization); sample++) {
// Looping over all particles.
for (int active = 0; active < n_particles; active++) {
// Using the quantum force to calculate a new position.
for (int i = 0; i < dim; i++)
r_new(active, i) = r_old(active, i) + D * q_force_old(active, i) * dt + DRanNormalZigVec() * sqrt(dt);
// Evaluating the Wave Function in r_new.
wf->set_r_new(r_new, active);
wf->evaluate_new();
// Updating the quantum force.
q_force_new = wf->q_force();
// Calculating the ratio between the Green's functions.
greens_function = 0;
for (int j = 0; j < dim; j++) {
greens_function += (q_force_old(active, j) + q_force_new(active, j))
* (D * dt * 0.5 * (q_force_old(active, j)
- q_force_new(active, j)) - r_new(active, j) + r_old(active, j));
}
greens_function = exp(0.5 * greens_function);
// Metropolis-Hastings acceptance test.
R = wf->get_ratio();
R = R * R *greens_function;
if (ran3(&idum) <= R) {
r_old = r_new;
q_force_old = q_force_new;
wf->accept_move();
if (sample > thermalization) {
accepted++;
delta_e = ht->get_energy(r_old);
}
} else {
// If the move is not accepted the position and quantum force is reset.
r_new = r_old;
q_force_new = q_force_old;
}
// Sampling the energy.
if (sample > thermalization) {
energy += delta_e;
energy_sq += delta_e*delta_e;
#if BLOCKING
blockfile.write((char*) &delta_e, sizeof (double));
#endif
}
}
} // End MC cycles.
// Scaling the results.
energy = energy / cycles / n_particles;
energy_sq = energy_sq / cycles / n_particles;
accepted /= n_particles;
#if BLOCKING
blockfile.close();
#endif
}