From 6ae3e36be081d52466bf7fc4a4fb84932acce3c3 Mon Sep 17 00:00:00 2001
From: David Seguin <davidseguin@live.ca>
Date: Wed, 12 Jan 2022 01:27:35 -0500
Subject: [PATCH] Performance: Cache NPC goal (#54312)

The goal cache is invalidated when the NPC moves to a different OMT.
---
 src/npc.h       |  7 +++++++
 src/npcmove.cpp | 36 ++++++++++++++++++++++--------------
 2 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/src/npc.h b/src/npc.h
index b05cd096dbf20..3fe34686c8830 100644
--- a/src/npc.h
+++ b/src/npc.h
@@ -591,6 +591,11 @@ struct npc_short_term_cache {
     cata::optional<int> closest_enemy_to_friendly_distance() const;
 };
 
+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).
@@ -1300,6 +1305,8 @@ class npc : public Character
         std::map<std::string, time_point> complaints;
 
         npc_short_term_cache ai_cache;
+
+        std::map<npc_need, npc_need_goal_cache> goal_cache;
     public:
         const std::shared_ptr<npc_attack> &get_current_attack() const {
             return ai_cache.current_attack;
diff --git a/src/npcmove.cpp b/src/npcmove.cpp
index fe5af77d66a2c..006d5bbcaf4b3 100644
--- a/src/npcmove.cpp
+++ b/src/npcmove.cpp
@@ -4190,20 +4190,28 @@ void npc::set_omt_destination()
 
     std::string dest_type;
     for( const auto &fulfill : needs ) {
-        // look for the closest occurrence of any of that locations terrain types
-        omt_find_params find_params;
-        for( const oter_type_str_id &elem : get_location_for( fulfill )->get_all_terrains() ) {
-            std::pair<std::string, ot_match_type> temp_pair;
-            temp_pair.first = elem.str();
-            temp_pair.second = ot_match_type::type;
-            find_params.types.push_back( temp_pair );
-        }
-        // 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 );
+        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_str_id &elem : get_location_for( fulfill )->get_all_terrains() ) {
+                std::pair<std::string, ot_match_type> temp_pair;
+                temp_pair.first = elem.str();
+                temp_pair.second = ot_match_type::type;
+                find_params.types.push_back( temp_pair );
+            }
+            // 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() );