Optimize distance calculation by getting rid of rounding

Project-OSRM · Apr 26, 2018 · b813444 · b813444
1 parent 7414e22
commit b813444
Showing 1 changed file with 20 additions and 11 deletions.
diff --git a/src/util/coordinate_calculation.cpp b/src/util/coordinate_calculation.cpp
@@ -27,26 +27,34 @@ class CheapRulerContainer
   public:
     CheapRulerContainer(const int number_of_rulers)
         : cheap_ruler_cache(number_of_rulers, mapbox::cheap_ruler::CheapRuler(0)),
-          step(90.0 / number_of_rulers)
+          step(90.0 * COORDINATE_PRECISION / number_of_rulers)
     {
         for (int n = 0; n < number_of_rulers; n++)
         {
             cheap_ruler_cache[n] = mapbox::cheap_ruler::CheapRuler(
-                step * (n + 0.5), mapbox::cheap_ruler::CheapRuler::Meters);
+                step * (n + 0.5) / COORDINATE_PRECISION, mapbox::cheap_ruler::CheapRuler::Meters);
         }
     };
-    mapbox::cheap_ruler::CheapRuler &getRuler(const double lat)
+
+    mapbox::cheap_ruler::CheapRuler &getRuler(const FixedLatitude lat_1, const FixedLatitude lat_2)
     {
-        return cheap_ruler_cache[std::min((int)std::floor(abs(lat) / step),
-                                          (int)cheap_ruler_cache.size() - 1)];
+        auto lat = (lat_1 + lat_2) / util::FixedLatitude{2};
+        return getRuler(lat);
+    }
+
+    mapbox::cheap_ruler::CheapRuler &getRuler(const FixedLatitude lat)
+    {
+        BOOST_ASSERT(step > 1);
+        auto bin = (std::abs(static_cast<int>(lat)) - 1) / step;
+        return cheap_ruler_cache[bin];
     };
 
   private:
     std::vector<mapbox::cheap_ruler::CheapRuler> cheap_ruler_cache;
-    const double step;
+    const int step;
 };
 CheapRulerContainer cheap_ruler_container(1800);
-}
+} // namespace
 
 // Does not project the coordinates!
 std::uint64_t squaredEuclideanDistance(const Coordinate lhs, const Coordinate rhs)
@@ -72,7 +80,8 @@ double fccApproximateDistance(const Coordinate coordinate_1, const Coordinate co
     const auto lat1 = static_cast<double>(util::toFloating(coordinate_1.lat));
     const auto lon2 = static_cast<double>(util::toFloating(coordinate_2.lon));
     const auto lat2 = static_cast<double>(util::toFloating(coordinate_2.lat));
-    return cheap_ruler_container.getRuler(0.5 * (lat1 + lat2)).distance({lon1, lat1}, {lon2, lat2});
+    return cheap_ruler_container.getRuler(coordinate_1.lat, coordinate_2.lat)
+        .distance({lon1, lat1}, {lon2, lat2});
 }
 
 double haversineDistance(const Coordinate coordinate_1, const Coordinate coordinate_2)
@@ -466,6 +475,6 @@ double computeArea(const std::vector<Coordinate> &polygon)
     return area / 2.;
 }
 
-} // ns coordinate_calculation
-} // ns util
-} // ns osrm
+} // namespace coordinate_calculation
+} // namespace util
+} // namespace osrm