/* Interface to the exclusive hypervolume contribution of a set of points.
*
* @param r_point [matrix]
* Matrix of points (each column contains one point).
* @param r_ref_point [numeric]
* Reference point, e.g., the nadir point.
* @return [numeric] Vector of hypervolume contributions.
**/
SEXP computeDominatedHypervolumeContributionC(SEXP r_points, SEXP r_ref_point) {
// unpack imcoming R data
// JB: compatibility of dimensions is checked in R
EXTRACT_NUMERIC_MATRIX(r_points, c_points, dim, n_points);
EXTRACT_NUMERIC_VECTOR(r_ref_point, c_ref_point, n_ref_point);
SEXP r_hvc = ALLOC_REAL_VECTOR(n_points);
double *c_hvc = REAL(r_hvc);
// Here we compute the hypervolume contribution with a naive approach.
// Let Y be the set of points. We iteratively compute the dominated hyper-
// volume for Y\{y} for all y in Y. After each iteration swap the first and the
// current column. This way we can always compute the hypervolumne of the points
// at locations 1, ..., n-1 and omit the first one at position 0.
// compute total hypervolume contribution
const double total_hv = fpli_hv(c_points, dim, n_points, c_ref_point);
// and now compute individual hv contribution
for (int i = 0; i < n_points; ++i) {
const double current_hv = fpli_hv(c_points + dim, dim, n_points - 1, c_ref_point);
c_hvc[i] = total_hv - current_hv;
// do the swaping (see above)
if (i != (n_points - 1)) {
for (int j = 0; j < dim; ++j) {
double tmp = c_points[dim * (i + 1) + j];
c_points[dim * (i + 1) + j] = c_points[j];
c_points[j] = tmp;
}
}
}
UNPROTECT(1);
return r_hvc;
}
/* Interface to hypervolume algorithm by Fonseca et al.
*
* @param r_points [matrix]
* Matrix of points (column-wise).
* @param ref.point [numeric}]
* Reference point.
* @return [numeric(1)] Dominated hypervolume.
**/
SEXP computeDominatedHypervolumeC(SEXP r_points, SEXP r_ref_point) {
// unpack R data
EXTRACT_NUMERIC_MATRIX(r_points, c_points, dim, n_points);
EXTRACT_NUMERIC_VECTOR(r_ref_point, c_ref_point, len_ref);
// allocate memory for Hypervolume value
SEXP r_hv = ALLOC_REAL_VECTOR(1);
double *c_hv = REAL(r_hv);
// call Fonseca et al. algorithm
c_hv[0] = fpli_hv(c_points, dim, n_points, c_ref_point);
// free memory and return
UNPROTECT(1);
return r_hv;
}
double hypervolume_compute(float **distances, int popsize, int nobj)
{
double *reference; /* Reference vector */
double *data; /* Reshaped vector */
double volume = 0; /* Hypervolume computation */
int i, j, k = 0;
/* Transpose the objective matrice*/
data = malloc(nobj * popsize * sizeof(double));
for (i=0;i<popsize;i++)
for (j=0;j<nobj;j++)
data[k++] = (double)distances[i][j];
reference = calloc(nobj, sizeof(double));
for (i = 0; i < nobj; i++)
reference[i] = 2;
volume = fpli_hv(data, nobj, popsize, reference);
free(data);
free(reference);
return volume;
}