--- /dev/null
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include <nlopt.h>
+
+typedef struct {
+ int N;
+ double *x, *y; /* length N; */
+} lorentzdata;
+
+static double sqr(double x) { return x * x; }
+
+static int count = 0;
+
+static double lorentzerr(int n, const double *p, double *grad, void *data)
+{
+ lorentzdata *d = (lorentzdata *) data;
+ int N = d->N;
+ const double *xs = d->x;
+ const double *ys = d->y;
+ double val = 0;
+ int i, j;
+
+ for (i = 0; i < N; ++i) {
+ double x = xs[i], y = ys[i];
+ double lorsum = 0;
+
+ for (j = 0; j < n; j += 3) {
+ double A = p[j + 0];
+ double w = p[j + 1];
+ double G = p[j + 2];
+ double lor = A / (sqr(x - w) + G*G);
+
+ lorsum += lor;
+ }
+
+ val += sqr(y - lorsum);
+
+ if (grad)
+ for (j = 0; j < n; j += 3) {
+ double A = p[j + 0];
+ double w = p[j + 1];
+ double G = p[j + 2];
+ double deninv = 1.0 / (sqr(x - w) + G*G);
+
+ grad[j + 0] += -2 * (y - lorsum) * deninv;
+ grad[j + 1] += 4*A * (w - x) * (y - lorsum) * sqr(deninv);
+ grad[j + 2] += 4*A * G * (y - lorsum) * sqr(deninv);
+ }
+ }
+ ++count;
+ // printf("%d: f(%g,%g,%g) = %g\n", count, p[0],p[1],p[2], val);
+ return val;
+}
+
+extern double nlopt_urand(double a, double b);
+
+int main(void)
+{
+ lorentzdata d;
+ int i;
+ double A = 1, w = 0, G = 1, noise=0.01;
+ double lb[3] = {-HUGE_VAL,-HUGE_VAL,0};
+ double ub[3] = {HUGE_VAL,HUGE_VAL,HUGE_VAL};
+ double p[3] = {0,1,2}, minf;
+
+ nlopt_srand_time();
+
+ d.N = 200;
+ d.x = (double *) malloc(sizeof(double) * d.N * 2);
+ d.y = d.x + d.N;
+ for (i = 0; i < d.N; ++i) {
+ d.x[i] = nlopt_urand(-0.5, 0.5) * 8*G + w;
+ d.y[i] = 2*noise*nlopt_urand(-0.5,0.5) + A / (sqr(d.x[i]-w) + G*G);
+ }
+
+ nlopt_minimize(NLOPT_LN_NEWUOA_BOUND, 3, lorentzerr, &d,
+ lb, ub, p, &minf,
+ -HUGE_VAL, 0,0, 1e-6,NULL, 0,0);
+
+ printf("%d minf=%g at A=%g, w=%g, G=%g\n", count, minf, p[0],p[1],p[2]);
+
+ count = 0;
+ nlopt_minimize(NLOPT_LN_COBYLA, 3, lorentzerr, &d,
+ lb, ub, p, &minf,
+ -HUGE_VAL, 0,0, 1e-6,NULL, 0,0);
+
+ printf("%d minf=%g at A=%g, w=%g, G=%g\n", count, minf, p[0],p[1],p[2]);
+
+ count = 0;
+ nlopt_minimize(NLOPT_LN_NELDERMEAD, 3, lorentzerr, &d,
+ lb, ub, p, &minf,
+ -HUGE_VAL, 0,0, 1e-6,NULL, 0,0);
+
+ printf("%d minf=%g at A=%g, w=%g, G=%g\n", count, minf, p[0],p[1],p[2]);
+
+ count = 0;
+ nlopt_minimize(NLOPT_LN_SBPLX, 3, lorentzerr, &d,
+ lb, ub, p, &minf,
+ -HUGE_VAL, 0,0, 1e-6,NULL, 0,0);
+
+ printf("%d minf=%g at A=%g, w=%g, G=%g\n", count, minf, p[0],p[1],p[2]);
+
+ return 0;
+}