insert-eject: iterate over nearest insertions only

Not optimal at 10 min (8 instances):
  c1_10_6: 100 (best: 99, diff: +1)
  c1_10_7: 98 (best: 97, diff: +1)
  c1_10_8: 93 (best: 92, diff: +1)
  c2_10_3: 29 (best: 28, diff: +1)
  c2_10_6: 30 (best: 29, diff: +1)
  c2_10_7: 30 (best: 29, diff: +1)
  c2_10_8: 29 (best: 28, diff: +1)
  c2_10_9: 29 (best: 28, diff: +1)

Not optimal at 60 min (5 instances):
  c1_10_6: 100 (best: 99, diff: +1)
  c1_10_8: 93 (best: 92, diff: +1)
  c2_10_7: 30 (best: 29, diff: +1)
  c2_10_8: 29 (best: 28, diff: +1)
  c2_10_9: 29 (best: 28, diff: +1)

Not optimal at 300 min (3 instances):
  c1_10_8: 93 (best: 92, diff: +1)
  c2_10_8: 29 (best: 28, diff: +1)
  c2_10_9: 29 (best: 28, diff: +1)

Author: Astronomax

src/eama_solver.c

@@ -225,20 +225,19 @@ insert_eject(struct solution *s)
 
 	int64_t p_best = INT64_MAX;
 	struct modification opt_insertion = modification_new(INSERT, NULL, s->w);
+	struct modification insertions[MAX_N_CUSTOMERS * 2];
+	int n_insertions = solution_collect_near_insertions(
+		s, s->w, options.n_near, insertions, MAX_N_CUSTOMERS * 2);
 	struct customer *ejection[MAX_N_CUSTOMERS];
 	int ejection_size = 0;
 	struct customer *opt_ejection[MAX_N_CUSTOMERS];
 	int opt_ejection_size = 0;
 
 	for (int i = 0; i < s->n_routes; i++) {
 		struct route *v_route = s->routes[i];
-		struct customer *v;
-		/* iterate over all possible insert positions in v_route */
-		rlist_foreach_entry(v, &v_route->list, in_route) {
-			if (v == depot_head(v_route))
-				continue;
-			struct modification m = modification_new(INSERT, v, s->w);
-			if (!modification_applicable(m))
+		for (int j = 0; j < n_insertions; j++) {
+			struct modification m = insertions[j];
+			if (m.v->route != v_route)
 				continue;
 			modification_apply(m);
 
@@ -253,8 +252,8 @@ insert_eject(struct solution *s)
 				    ejection, &ejection_size, &p_best);
 			while(!fiber_is_dead(f)) {
 				opt_insertion = m;
-				for (int j = 0; j < ejection_size; j++)
-					opt_ejection[j] = ejection[j];
+				for (int k = 0; k < ejection_size; k++)
+					opt_ejection[k] = ejection[k];
 				opt_ejection_size = ejection_size;
 				fiber_call(f);
 			}

src/solution.cc

@@ -552,6 +552,41 @@ solution_find_optimal_insertion(struct solution *s, struct customer *w,
 	return opt_modification;
 }
 
+int
+solution_collect_near_insertions(struct solution *s, struct customer *w,
+				 int n_near, struct modification *mods,
+				 int max_mods)
+{
+	assert(is_ejected(w));
+	if (!solution_global_initialized)
+		solution_global_init();
+
+	int count = 0;
+	customer *v;
+	int limit = MIN(n_near, p.n_customers);
+	for (int i = 0; i < limit; i++) {
+		int id = neighbours_sorted[w->id][i];
+		assert(id != 0);
+		v = s->meta->idx[id];
+		struct modification m = modification_new(INSERT, v, w);
+		if (!modification_applicable(m))
+			continue;
+		assert(count < max_mods);
+		mods[count++] = m;
+	}
+
+	for (int i = 0; i < s->n_routes; i++) {
+		v = depot_tail(s->routes[i]);
+		struct modification m = modification_new(INSERT, v, w);
+		if (!modification_applicable(m))
+			continue;
+		assert(count < max_mods);
+		mods[count++] = m;
+	}
+
+	return count;
+}
+
 struct customer *
 solution_find_customer_by_id(struct solution *s, int id)
 {

src/solution.h

@@ -95,6 +95,11 @@ struct modification
 solution_find_optimal_insertion(struct solution *s, struct customer *w,
 				double alpha, double beta);
 
+int
+solution_collect_near_insertions(struct solution *s, struct customer *w,
+				 int n_near, struct modification *mods,
+				 int max_mods);
+
 struct customer *
 solution_find_customer_by_id(struct solution *s, int id);