From 439ad4a7c8278ed5208add0c42b478547952cdad Mon Sep 17 00:00:00 2001
From: ThorstenB <brehmt@gmail.com>
Date: Sat, 24 Nov 2012 12:06:20 +0100
Subject: [PATCH] Traffic performance: cache track length Track length is
 calculate every iteration/for every aircraft. Since some tracks have hundreds
 of waypoints, calculation is slow. Cache the track length between the
 waypoints ahead, so it rarely needs to be recalculated.

---
 src/AIModel/AIAircraft.cxx | 13 ++++++++++++-
 src/AIModel/AIAircraft.hxx |  7 +++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/AIModel/AIAircraft.cxx b/src/AIModel/AIAircraft.cxx
index d2aac7502..762240247 100644
--- a/src/AIModel/AIAircraft.cxx
+++ b/src/AIModel/AIAircraft.cxx
@@ -94,6 +94,8 @@ FGAIAircraft::FGAIAircraft(FGAISchedule *ref) :
     _performance = 0; //TODO initialize to JET_TRANSPORT from PerformanceDB
     dt = 0;
     takeOffStatus = 0;
+
+    trackCache.remainingLength = 0;
 }
 
 
@@ -1347,7 +1349,16 @@ time_t FGAIAircraft::checkForArrivalTime(const string& wptName) {
      FGAIWaypoint* curr = 0;
      curr = fp->getCurrentWaypoint();
 
-     double tracklength = fp->checkTrackLength(wptName);
+     // don't recalculate tracklength unless the start/stop waypoint has changed
+     if (curr &&
+         ((curr->getName() != trackCache.startWptName)||
+          (wptName != trackCache.finalWptName)))
+     {
+         trackCache.remainingLength = fp->checkTrackLength(wptName);
+         trackCache.startWptName = curr->getName();
+         trackCache.finalWptName = wptName;
+     }
+     double tracklength = trackCache.remainingLength;
      if (tracklength > 0.1) {
           tracklength += fp->getDistanceToGo(pos.getLatitudeDeg(), pos.getLongitudeDeg(), curr);
      } else {
diff --git a/src/AIModel/AIAircraft.hxx b/src/AIModel/AIAircraft.hxx
index 9d8fc8e5e..3ce0d6283 100644
--- a/src/AIModel/AIAircraft.hxx
+++ b/src/AIModel/AIAircraft.hxx
@@ -184,6 +184,13 @@ private:
     PerformanceData* _performance; // the performance data for this aircraft
     
    void assertSpeed(double speed);
+
+   struct
+   {
+       double remainingLength;
+       std::string startWptName;
+       std::string finalWptName;
+   } trackCache;
 };
 
 
-- 
2.39.5