- irns = alloca((ou->node_count-1) * sizeof(*irns));
- curr = bitset_alloca(ou->node_count-1);
-
- /* brute force the best set */
- bitset_set_all(curr);
- while ((max = bitset_popcnt(curr)) != 0) {
- /* check if curr is a stable set */
- int i, o, is_stable_set = 1;
- bitset_foreach(curr, pos)
- irns[pos] = ou->nodes[1+pos];
- for(i=0; i<max; ++i)
- for(o=i+1; o<max; ++o) /* !!!!! difference to qnode_max_ind_set(): NOT o=i */
- if (nodes_interfere(ou->co->chordal_env, irns[i], irns[o])) {
- is_stable_set = 0;
+ /* assign the nodes into two groups.
+ * safe: node has no interference, hence it is in every max stable set.
+ * unsafe: node has an interference
+ */
+ safe = alloca((ou->node_count-1) * sizeof(*safe));
+ safe_costs = 0;
+ safe_count = 0;
+ unsafe = alloca((ou->node_count-1) * sizeof(*unsafe));
+ unsafe_costs = alloca((ou->node_count-1) * sizeof(*unsafe_costs));
+ unsafe_count = 0;
+ for(i=1; i<ou->node_count; ++i) {
+ int is_safe = 1;
+ for(o=1; o<ou->node_count; ++o) {
+ if (i==o)
+ continue;
+ if (nodes_interfere(chordal_env, ou->nodes[i], ou->nodes[o])) {
+ unsafe_costs[unsafe_count] = ou->costs[i];
+ unsafe[unsafe_count] = ou->nodes[i];
+ ++unsafe_count;
+ is_safe = 0;
+ break;
+ }
+ }
+ if (is_safe) {
+ safe_costs += ou->costs[i];
+ safe[safe_count++] = ou->nodes[i];
+ }
+ }
+
+
+ /* now compute the best set out of the unsafe nodes*/
+ if (unsafe_count > MIS_HEUR_TRIGGER) {
+ bitset_t *best = bitset_alloca(unsafe_count);
+ /* Heuristik: Greedy trial and error form index 0 to unsafe_count-1 */
+ for (i=0; i<unsafe_count; ++i) {
+ bitset_set(best, i);
+ /* check if it is a stable set */
+ for (o=bitset_next_set(best, 0); o!=-1 && o<i; o=bitset_next_set(best, o+1))
+ if (nodes_interfere(chordal_env, unsafe[i], unsafe[o])) {
+ bitset_clear(best, i); /* clear the bit and try next one */