perf(port): cache NPC goal (#4225)

* Update npc.h

Co-authored-by: David Seguin <davidseguin@live.ca>

* Update npcmove.cpp

Co-authored-by: David Seguin <davidseguin@live.ca>

* fix: add missing comments, use emplace_back

---------

Co-authored-by: David Seguin <davidseguin@live.ca>
Co-authored-by: scarf <greenscarf005@gmail.com>

src/npc.h

@@ -536,6 +536,11 @@ struct npc_short_term_cache {
     lru_cache<tripoint, int> searched_tiles;
 };
 
+struct npc_need_goal_cache {
+    tripoint_abs_omt goal;
+    tripoint_abs_omt omt_loc;
+};
+
 // DO NOT USE! This is old, use strings as talk topic instead, e.g. "TALK_AGREE_FOLLOW" instead of
 // TALK_AGREE_FOLLOW. There is also convert_talk_topic which can convert the enumeration values to
 // the new string values (used to load old saves).
@@ -1245,6 +1250,8 @@ class npc : public player
         std::map<std::string, time_point> complaints;
 
         npc_short_term_cache ai_cache;
+
+        std::map<npc_need, npc_need_goal_cache> goal_cache;
     public:
         /**
          * Global position, expressed in map square coordinate system

src/npcmove.cpp

@@ -4260,24 +4260,25 @@ void npc::set_omt_destination()
 
     std::string dest_type;
     for( const auto &fulfill : needs ) {
-        // look for the closest occurence of any of that locations terrain types
-        std::vector<oter_type_id> loc_list = get_location_for( fulfill )->get_all_terrains();
-        std::shuffle( loc_list.begin(), loc_list.end(), rng_get_engine() );
-        omt_find_params find_params;
-        std::vector<std::pair<std::string, ot_match_type>> temp_types;
-        for( const oter_type_id &elem : loc_list ) {
-            std::pair<std::string, ot_match_type> temp_pair;
-            temp_pair.first = elem.id().str();
-            temp_pair.second = ot_match_type::type;
-            temp_types.push_back( temp_pair );
-        }
-        find_params.search_range = 75;
-        find_params.min_distance = 0;
-        find_params.must_see = false;
-        find_params.cant_see = false;
-        find_params.types = temp_types;
-        find_params.existing_only = false;
-        goal = overmap_buffer.find_closest( surface_omt_loc, find_params );
+        auto cache_iter = goal_cache.find( fulfill );
+        if( cache_iter != goal_cache.end() && cache_iter->second.omt_loc == surface_omt_loc ) {
+            goal = cache_iter->second.goal;
+        } else {
+            // look for the closest occurrence of any of that locations terrain types
+            omt_find_params find_params;
+            for( const oter_type_id &elem : get_location_for( fulfill )->get_all_terrains() ) {
+                find_params.types.emplace_back( elem.id().str(), ot_match_type::type );
+            }
+            // note: no shuffle of `find_params.types` is needed, because `find_closest`
+            // disregards `types` order anyway, and already returns random result among
+            // those having equal minimal distance
+            find_params.search_range = 75;
+            find_params.existing_only = false;
+            goal = overmap_buffer.find_closest( surface_omt_loc, find_params );
+            npc_need_goal_cache &cache = goal_cache[fulfill];
+            cache.goal = goal;
+            cache.omt_loc = surface_omt_loc;
+        }
         omt_path.clear();
         if( goal != overmap::invalid_tripoint ) {
             omt_path = overmap_buffer.get_travel_path( surface_omt_loc, goal, overmap_path_params::for_npc() );