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Optimize distance calculation by getting rid of rounding

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Patrick Niklaus 2018-04-26 20:38:17 +00:00 committed by Patrick Niklaus
parent 41c31a2388
commit be24689b0f
1 changed files with 22 additions and 11 deletions
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33
src/util/coordinate_calculation.cpp
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@ -27,26 +27,36 @@ class CheapRulerContainer
public: public:
CheapRulerContainer(const int number_of_rulers) CheapRulerContainer(const int number_of_rulers)
: cheap_ruler_cache(number_of_rulers, mapbox::cheap_ruler::CheapRuler(0)), : 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++) for (int n = 0; n < number_of_rulers; n++)
{ {
cheap_ruler_cache[n] = mapbox::cheap_ruler::CheapRuler( 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), auto lat = (lat_1 + lat_2) / util::FixedLatitude{2};
(int)cheap_ruler_cache.size() - 1)]; return getRuler(lat);
}
mapbox::cheap_ruler::CheapRuler &getRuler(const FixedLatitude lat)
{
BOOST_ASSERT(step > 2);
// the |lat| > 0 -> |lat|-1 > -1 -> (|lat|-1)/step > -1/step > -1/2 >= -1 -> bin >= 0
std::size_t bin = (std::abs(static_cast<int>(lat)) - 1) / step;
BOOST_ASSERT(bin < cheap_ruler_cache.size());
return cheap_ruler_cache[bin];
}; };
private: private:
std::vector<mapbox::cheap_ruler::CheapRuler> cheap_ruler_cache; std::vector<mapbox::cheap_ruler::CheapRuler> cheap_ruler_cache;
const double step; const int step;
}; };
CheapRulerContainer cheap_ruler_container(1800); CheapRulerContainer cheap_ruler_container(1800);
} } // namespace
// Does not project the coordinates! // Does not project the coordinates!
std::uint64_t squaredEuclideanDistance(const Coordinate lhs, const Coordinate rhs) std::uint64_t squaredEuclideanDistance(const Coordinate lhs, const Coordinate rhs)
@ -72,7 +82,8 @@ double fccApproximateDistance(const Coordinate coordinate_1, const Coordinate co
const auto lat1 = static_cast<double>(util::toFloating(coordinate_1.lat)); const auto lat1 = static_cast<double>(util::toFloating(coordinate_1.lat));
const auto lon2 = static_cast<double>(util::toFloating(coordinate_2.lon)); const auto lon2 = static_cast<double>(util::toFloating(coordinate_2.lon));
const auto lat2 = static_cast<double>(util::toFloating(coordinate_2.lat)); 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) double haversineDistance(const Coordinate coordinate_1, const Coordinate coordinate_2)
@ -466,6 +477,6 @@ double computeArea(const std::vector<Coordinate> &polygon)
return area / 2.; return area / 2.;
} }
} // ns coordinate_calculation } // namespace coordinate_calculation
} // ns util } // namespace util
} // ns osrm } // namespace osrm