Dear NLopt developers/user community,
Thank you for this excellent library, I enjoyed a lot using it. However, I
have a question - some of the global optimization method do not work in my
case. In fact, I have no problems with NLOPT_AUGLAG_EQ, NLOPT_AUGLAG,
NLOPT_GN_ISRES, NLOPT_GN_CRS2_LM. Other methods like DIRECT, ESCH, MLSL do
not work in my case - the energy function is calculated, but the algorithm
somehow is not converged. Below is the example of my code:
void OPTIMIZESTRUCTURENLOPT (Conformer **conformer,
long int NBONDS, Fragment *fragments,
long int NATOMS, long int ITER, double TESTSIZE) {
// printf("Start of opt\n");
long int i1, j, ii;
nlopt_opt opt;
opt = nlopt_create(NLOPT_GN_ESCH, NBONDS);
nlopt_set_min_objective(opt, ENERGYNLOPT, (void *) (*conformer));
nlopt_set_xtol_rel(opt, 1e-3);
// the initial guess
(**conformer).IT=0;
double *x = malloc(NBONDS*sizeof(double)); // [NBONDS];
double *dx = malloc(NBONDS*sizeof(double)); //[NBONDS];
double *lb = malloc(NBONDS*sizeof(double));
double *ub = malloc(NBONDS*sizeof(double));
for (i1=0;i1<NBONDS;i1++) {
x[i1] = (**conformer).angles[i1];
dx[i1] = 0.1;
lb[i1] = -360;
ub[i1] = 360;
}
nlopt_set_initial_step(opt, dx);
nlopt_set_lower_bounds(opt, lb);
nlopt_set_upper_bounds(opt, ub);
// printf ("Start: ");
for (i1=0;i1<NBONDS;i1++) {
// printf ("%f ", x[i1]);
}
// printf ("\n");
//////////////////////////////////////////////
nlopt_opt opt_loc;
opt_loc = nlopt_create(NLOPT_LN_PRAXIS, NBONDS);
nlopt_set_local_optimizer(opt, opt_loc);
nlopt_set_xtol_rel(opt_loc, 1e-5);
nlopt_set_ftol_rel(opt_loc, 1e-5);
double minf; // the energy function value
if (nlopt_optimize(opt, x, &minf) < 0) {
printf ("nlopt failed!\n");
}
else {
printf ("found minimum after (%li) iterations = %0.010g\n",
(**conformer).IT, minf);
for (i1=0;i1<NBONDS;i1++) {
// printf ("%f ", x[i1]);
}
// printf ("\n");
}
And this is the energy function calls:
Iter: 10047 E = -1629.325853 Iter: 10048 E = -1629.325853 Iter: 10049 E =
-1629.325853 Iter: 10050 E = -1629.325853 Iter: 10051 E = -1628.944283
Iter: 10052 E = -1629.325853 Iter: 10053 E = -1629.325853 Iter: 10054 E =
-1628.997908 Iter: 10055 E = -1629.325853 Iter: 10056 E = -1629.325853
Iter: 10057 E = -1629.325853 Iter: 10058 E = -1629.325853 Iter: 10059 E =
-1629.325853 Iter: 10060 E = -1629.325853 Iter: 10061 E = -1629.325853
Iter: 10062 E = -1629.325853 Iter: 10063 E = -1629.325853 Iter: 10064 E =
-1629.325853 Iter: 10065 E = -1629.325853 Iter: 10066 E = -1629.325853
Iter: 10067 E = -1629.325853 Iter: 10068 E = -1629.325853 Iter: 10069 E =
-1629.325853 Iter: 10070 E = -1628.745543 Iter: 10071 E = -1629.325853
Iter: 10072 E = -1629.325853 Iter: 10073 E = -1629.325853 Iter: 10074 E =
-1629.325853 Iter: 10075 E = -1629.325853 Iter: 10076 E = -1629.325853
Iter: 10077 E = -1628.540874 Iter: 10078 E = -1629.325853 Iter: 10079 E =
-1629.325853 Iter: 10080 E = -1629.325853
Also, I observe the memory leak when trying to run direct - the memory just
growing up when the calculation is done.
May be I have forgotten to specify something? Sorry if the question is too
primitive, I am mainly a chemist by my background.
With kind regards,
Yury
PS - I also posted this question on stack overflow -
http://stackoverflow.com/questions/37645139/global-optimization-algorithms-in-nlopt
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