Dear all,
I am unable to compile my code with the nlopt library. My code is based on
the tutorial example (below). I compile with gcc -lnlopt main.c and get
several errors:
main.c:(.text+0x2a): undefined reference to `nlopt_create'
main.c:(.text+0x41): undefined reference to `nlopt_set_lower_bounds'
main.c:(.text+0x57): undefined reference to `nlopt_set_min_objective'
main.c:(.text+0xa7): undefined reference to
`nlopt_add_inequality_constraint'
main.c:(.text+0xc8): undefined reference to
`nlopt_add_inequality_constraint'
main.c:(.text+0xdc): undefined reference to `nlopt_set_xtol_rel'
main.c:(.text+0x10f): undefined reference to `nlopt_optimize'
main.c:(.text+0x166): undefined reference to `nlopt_destroy'
The library is installed in /usr/local/lib and the header files are at
/usr/local/include. My system administrator has added the library path
to `/etc/ld.so.conf'.
I'm running Debian GNU/Linux 6.0. My code is
#include <stdio.h>
#include <math.h>
#include "nlopt.h"
double myfunc(unsigned n, const double *x, double *grad, void*my_func_data);
double myconstraint(unsigned n, const double *x, double *grad, void *data);
typedef struct {
double a, b;
} my_constraint_data;
int count = 0;
int main(void){
double lb[2] = { -HUGE_VAL, 0 }; /* lower bounds */
nlopt_opt opt; /* create an `object' of type nlopt (an opaque pointer
type) */
opt = nlopt_create(NLOPT_LN_COBYLA, 2); /* algorithm and dimensionality
*/
nlopt_set_lower_bounds(opt, lb);
nlopt_set_min_objective(opt, myfunc, NULL);
/* add two inequality constraints */
my_constraint_data data[2] = { {2,0}, {-1,1} };
nlopt_add_inequality_constraint(opt, myconstraint, &data[0], 1e-8);
nlopt_add_inequality_constraint(opt, myconstraint, &data[1], 1e-8);
nlopt_set_xtol_rel(opt, 1e-4); /* set stopping criterion */
double x[2] = { 1.234, 5.678 }; /* some initial guess */
double minf; /* the minimum objective value, upon return */
if (nlopt_optimize(opt, x, &minf) < 0) {
printf("nlopt failed!\n");
}
else {
printf("found minimum at f(%g,%g) = %0.10g\n", x[0], x[1], minf);
}
printf("No of function evaluations = %d\n", count);
nlopt_destroy(opt);
}
double myfunc(unsigned n, const double *x, double *grad, void *my_func_data)
{
++count;
if (grad) {
grad[0] = 0.0;
grad[1] = 0.5 / sqrt(x[1]);
}
return sqrt(x[1]);
}
double myconstraint(unsigned n, const double *x, double *grad, void *data)
{
my_constraint_data *d = (my_constraint_data *) data;
double a = d->a, b = d->b;
if (grad) {
grad[0] = 3 * a * (a*x[0] + b) * (a*x[0] + b);
grad[1] = -1.0;
}
return ((a*x[0] + b) * (a*x[0] + b) * (a*x[0] + b) - x[1]);
}
Many thanks for your help,
James
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