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qmc-lttc/qmc_gaussian.c
2021-06-09 14:48:05 +02:00

45 lines
913 B
C

#include "qmc_stats.h"
#include "hydrogen.h"
double gaussian(double *r) {
const double norm_gauss = 1.0 / pow(2.0 * acos(-1.0), 1.5);
return norm_gauss * exp(-0.5 * (r[0]*r[0] + r[1]*r[1] + r[2]*r[2]));
}
double gaussian_montecarlo(double a, const int nmax) {
double r[3], energy, norm, w;
norm = 0.0;
energy = 0.0;
for (int i = 0; i < nmax; ++i) {
random_gauss(r, 3);
w = psi(a, r, 3) * psi(a, r, 3) / gaussian(r);
norm += w;
energy += w * e_loc(a, r, 3);
}
return energy / norm;
}
int main() {
const double a = 1.2;
const long nmax = 1e5;
int nruns = 30;
srand(time(NULL));
double x[nruns], obs[2];
for (int i = 0; i < nruns; ++i) {
x[i] = gaussian_montecarlo(a, nmax);
}
ave_error(x, nruns, obs);
printf("E = %.5lf +/- %.5lf\n", obs[0], obs[1]);
return 0;
}