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qmc-lttc/qmc_uniform.c
2021-04-25 20:02:47 +02:00

45 lines
852 B
C

#include "hydrogen.h"
#include "qmc_stats.h"
#include <stdlib.h>
#include <time.h>
double uniform_montecarlo(double a, const int nmax) {
double r[3], energy, norm, w, rnd;
norm = 0.0;
energy = 0.0;
for (int i = 0; i < nmax; ++i) {
for (int j = 0; j < 3; ++j) {
rnd = (double) rand() / RAND_MAX;
r[j] = -5.0 + 10.0 * rnd;
}
w = psi(a, r, 3) * psi(a, r, 3);
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] = uniform_montecarlo(a, nmax);
}
ave_error(x, nruns, obs);
printf("E = %.5lf +/- %.5lf\n", obs[0], obs[1]);
return 0;
}