/* add the coloring constraint */
cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_equal, 1.0);
bitset_foreach(colors, col) {
int var_idx = lpp_add_var(ienv->lp, name_cdd(buf, 'x', node_nr, col), lpp_binary, 0.0);
/* add the coloring constraint */
cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_equal, 1.0);
bitset_foreach(colors, col) {
int var_idx = lpp_add_var(ienv->lp, name_cdd(buf, 'x', node_nr, col), lpp_binary, 0.0);