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reduce coordinate_extraction overhead. slowdown reduced by 30 percent

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This commit is contained in:
Moritz Kobitzsch
2016-11-03 16:14:04 +01:00
parent 88208bfa5d
commit e84a0ea37c
3 changed files with 186 additions and 92 deletions
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src/extractor/guidance/coordinate_extractor.cpp
+163 -86
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@@ -32,7 +32,7 @@ const constexpr double LOOKAHEAD_DISTANCE_WITHOUT_LANES = 10.0;
// smaller widths, ranging from 2.5 to 3.25 meters. As a compromise, we use
// the 3.25 here for our angle calculations
const constexpr double ASSUMED_LANE_WIDTH = 3.25;
const constexpr double FAR_LOOKAHEAD_DISTANCE = 30.0;
const constexpr double FAR_LOOKAHEAD_DISTANCE = 20.0;
// The count of lanes assumed when no lanes are present. Since most roads will have lanes for both
// directions or a lane count specified, we use 2. Overestimating only makes our calculations safer,
@@ -70,15 +70,15 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
if (coordinates.size() <= 2)
return coordinates.back();
// due to repeated coordinates / smaller offset errors we skip over the very first parts of the
// coordinate set to add a small level of fault tolerance
const constexpr double distance_to_skip_over_due_to_coordinate_inaccuracies = 2;
// fallback, mostly necessary for dead ends
if (intersection_node == to_node)
return TrimCoordinatesToLength(coordinates, 5).back();
const auto lookahead_distance =
FAR_LOOKAHEAD_DISTANCE + considered_lanes * ASSUMED_LANE_WIDTH * 0.5;
// reduce coordinates to the ones we care about
coordinates = TrimCoordinatesToLength(std::move(coordinates), lookahead_distance);
return TrimCoordinatesToLength(std::move(coordinates),
distance_to_skip_over_due_to_coordinate_inaccuracies)
.back();
// If this reduction leaves us with only two coordinates, the turns/angles are represented in a
// valid way. Only curved roads and other difficult scenarios will require multiple coordinates.
@@ -86,6 +86,13 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
return coordinates.back();
const auto &turn_edge_data = node_based_graph.GetEdgeData(turn_edge);
// roundabouts, check early to avoid other costly checks
if (turn_edge_data.roundabout)
return TrimCoordinatesToLength(std::move(coordinates),
distance_to_skip_over_due_to_coordinate_inaccuracies)
.back();
const util::Coordinate turn_coordinate =
node_coordinates[traversed_in_reverse ? to_node : intersection_node];
@@ -94,8 +101,11 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
if (turn_edge_data.road_classification.IsLowPriorityRoadClass())
{
// Look ahead a tiny bit. Low priority road classes can be modelled fairly distinct in the
// very first part of the road
coordinates = TrimCoordinatesToLength(std::move(coordinates), 10);
// very first part of the road. It's less accurate than searching for offsets but the models
// contained in OSM are just to strange to capture fully. Using the fallback here we try to
// do the best of what we can.
coordinates =
TrimCoordinatesToLength(std::move(coordinates), LOOKAHEAD_DISTANCE_WITHOUT_LANES);
if (coordinates.size() > 2 &&
util::coordinate_calculation::haversineDistance(turn_coordinate, coordinates[1]) <
ASSUMED_LANE_WIDTH)
@@ -104,6 +114,29 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
return coordinates.back();
}
const auto first_distance =
util::coordinate_calculation::haversineDistance(coordinates[0], coordinates[1]);
/* if the very first coordinate along the road is reasonably far away from the road, we assume
* the coordinate to correctly represent the turn. This could probably be improved using
* information on the very first turn angle (requires knowledge about previous road) and the
* respective lane widths.
*/
const bool first_coordinate_is_far_away = [&first_distance, considered_lanes]() {
const auto required_distance =
considered_lanes * 0.5 * ASSUMED_LANE_WIDTH + LOOKAHEAD_DISTANCE_WITHOUT_LANES;
return first_distance > required_distance;
}();
if (first_coordinate_is_far_away)
{
return coordinates[1];
}
// now, after the simple checks have succeeded make our further computations simpler
const auto lookahead_distance =
FAR_LOOKAHEAD_DISTANCE + considered_lanes * ASSUMED_LANE_WIDTH * 0.5;
/*
* The coordinates along the road are in different distances from the source. If only very few
* coordinates are close to the intersection, It might just be we simply looked to far down the
@@ -120,39 +153,18 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
* of the actual roads. If a road splits in two, the ways for the separate direction can be
* modeled very far apart with a steep angle at the split, even though the roads actually don't
* take a turn. The distance between the coordinates can be an indicator for these small changes
*
* Luckily, these segment distances are a byproduct of trimming
*/
const auto segment_distances = [&coordinates]() {
std::vector<double> segment_distances;
segment_distances.reserve(coordinates.size());
// sentinel
auto last_coordinate = coordinates.front();
boost::range::transform(coordinates,
std::back_inserter(segment_distances),
[&last_coordinate](const util::Coordinate current_coordinate) {
const auto distance =
util::coordinate_calculation::haversineDistance(
last_coordinate, current_coordinate);
last_coordinate = current_coordinate;
return distance;
});
return segment_distances;
}();
auto segment_distances = PrepareLengthCache(coordinates, lookahead_distance);
coordinates =
TrimCoordinatesToLength(std::move(coordinates), lookahead_distance, segment_distances);
segment_distances.back() = std::min(segment_distances.back(), lookahead_distance);
BOOST_ASSERT(segment_distances.size() == coordinates.size());
/* if the very first coordinate along the road is reasonably far away from the road, we assume
* the coordinate to correctly represent the turn. This could probably be improved using
* information on the very first turn angle (requires knowledge about previous road) and the
* respective lane widths.
*/
const bool first_coordinate_is_far_away = [&segment_distances, considered_lanes]() {
const auto required_distance =
considered_lanes * 0.5 * ASSUMED_LANE_WIDTH + LOOKAHEAD_DISTANCE_WITHOUT_LANES;
return segment_distances[1] > required_distance;
}();
if (first_coordinate_is_far_away)
{
return coordinates[1];
}
// if we are now left with two, well than we don't have to worry
if (coordinates.size() == 2)
return coordinates.back();
const double max_deviation_from_straight = GetMaxDeviation(
coordinates.begin(), coordinates.end(), coordinates.front(), coordinates.back());
@@ -160,9 +172,7 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
// if the deviation from a straight line is small, we can savely use the coordinate. We use half
// a lane as heuristic to determine if the road is straight enough.
if (max_deviation_from_straight < 0.5 * ASSUMED_LANE_WIDTH)
{
return coordinates.back();
}
/*
* if a road turns barely in the beginning, it is similar to the first coordinate being
@@ -194,10 +204,11 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
return straight_distance >=
considered_lanes * 0.5 * ASSUMED_LANE_WIDTH + LOOKAHEAD_DISTANCE_WITHOUT_LANES;
}();
if (starts_of_without_turn)
{
// skip over repeated coordinates
return TrimCoordinatesToLength(std::move(coordinates), 5).back();
return TrimCoordinatesToLength(std::move(coordinates), 5, segment_distances).back();
}
// compute the regression vector based on the sum of least squares
@@ -234,21 +245,6 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
const auto total_distance =
std::accumulate(segment_distances.begin(), segment_distances.end(), 0.);
if (IsDirectOffset(coordinates,
straight_index,
straight_distance,
total_distance,
segment_distances,
considered_lanes))
{
// could be too agressive? Depend on lanes to check how far we want to go out?
// compare
// http://www.openstreetmap.org/search?query=52.411243%2013.363575#map=19/52.41124/13.36357
const auto offset_index = std::max<decltype(straight_index)>(1, straight_index);
return GetCorrectedCoordinate(
turn_coordinate, coordinates[offset_index], coordinates[offset_index + 1]);
}
if (IsCurve(coordinates,
segment_distances,
total_distance,
@@ -263,13 +259,31 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
* destination lanes and the ones that performa a larger turn.
*/
const double offset = 0.5 * considered_lanes * ASSUMED_LANE_WIDTH;
coordinates = TrimCoordinatesToLength(std::move(coordinates), offset);
coordinates = TrimCoordinatesToLength(std::move(coordinates), offset, segment_distances);
segment_distances.resize(coordinates.size());
segment_distances.back() = offset;
const auto vector_head = coordinates.back();
coordinates = TrimCoordinatesToLength(std::move(coordinates), offset);
coordinates =
TrimCoordinatesToLength(std::move(coordinates), 0.5 * offset, segment_distances);
BOOST_ASSERT(coordinates.size() >= 2);
return GetCorrectedCoordinate(turn_coordinate, coordinates.back(), vector_head);
}
if (IsDirectOffset(coordinates,
straight_index,
straight_distance,
total_distance,
segment_distances,
considered_lanes))
{
// could be too agressive? Depend on lanes to check how far we want to go out?
// compare
// http://www.openstreetmap.org/search?query=52.411243%2013.363575#map=19/52.41124/13.36357
const auto offset_index = std::max<decltype(straight_index)>(1, straight_index);
return GetCorrectedCoordinate(
turn_coordinate, coordinates[offset_index], coordinates[offset_index + 1]);
}
{
// skip over the first coordinates, in specific the assumed lane count. We add a small
// safety factor, to not overshoot on the regression
@@ -296,7 +310,9 @@ CoordinateExtractor::GetCoordinateAlongRoad(const NodeID intersection_node,
// We use the locations on the regression line to offset the regression line onto the
// intersection.
return TrimCoordinatesToLength(coordinates, LOOKAHEAD_DISTANCE_WITHOUT_LANES).back();
return TrimCoordinatesToLength(
std::move(coordinates), LOOKAHEAD_DISTANCE_WITHOUT_LANES, segment_distances)
.back();
}
std::vector<util::Coordinate>
@@ -484,7 +500,7 @@ bool CoordinateExtractor::IsCurve(const std::vector<util::Coordinate> &coordinat
if ((distance_to_max_deviation <= 0.35 * segment_length ||
maximum_deviation < std::max(0.3 * considered_lane_width, 0.5 * ASSUMED_LANE_WIDTH)) &&
segment_length > 10)
segment_length > LOOKAHEAD_DISTANCE_WITHOUT_LANES)
return false;
BOOST_ASSERT(coordinates.size() >= 3);
@@ -599,42 +615,102 @@ bool CoordinateExtractor::IsDirectOffset(const std::vector<util::Coordinate> &co
coordinates.back());
}
std::vector<double>
CoordinateExtractor::PrepareLengthCache(const std::vector<util::Coordinate> &coordinates,
const double limit) const
{
BOOST_ASSERT(!coordinates.empty());
BOOST_ASSERT(limit >= 0);
std::vector<double> segment_distances;
segment_distances.reserve(coordinates.size());
segment_distances.push_back(0);
// sentinel
auto last_coordinate = coordinates.front();
std::find_if(
std::next(std::begin(coordinates)),
std::end(coordinates),
[&last_coordinate, limit, &segment_distances](const util::Coordinate current_coordinate) {
const auto distance = util::coordinate_calculation::haversineDistance(
last_coordinate, current_coordinate);
last_coordinate = current_coordinate;
segment_distances.push_back(distance);
return distance >= limit;
});
return segment_distances;
}
std::vector<util::Coordinate>
CoordinateExtractor::TrimCoordinatesToLength(std::vector<util::Coordinate> coordinates,
const double desired_length) const
const double desired_length,
const std::vector<double> &length_cache) const
{
BOOST_ASSERT(coordinates.size() >= 2);
BOOST_ASSERT(desired_length >= 0);
double distance_to_current_coordinate = 0;
std::size_t coordinate_index = 0;
for (std::size_t coordinate_index = 1; coordinate_index < coordinates.size();
++coordinate_index)
const auto compute_length =
[&coordinate_index, &distance_to_current_coordinate, &coordinates]() {
const auto new_distance =
distance_to_current_coordinate +
util::coordinate_calculation::haversineDistance(coordinates[coordinate_index - 1],
coordinates[coordinate_index]);
return new_distance;
};
const auto read_length_from_cache = [&length_cache, &coordinate_index]() {
return length_cache[coordinate_index];
};
bool use_cache = !length_cache.empty();
if (use_cache && length_cache.back() < desired_length && coordinates.size() >= 2)
{
const auto distance_to_next_coordinate =
distance_to_current_coordinate +
util::coordinate_calculation::haversineDistance(coordinates[coordinate_index - 1],
coordinates[coordinate_index]);
if (coordinates.size() == length_cache.size())
return coordinates;
// if we reached the number of coordinates, we can stop here
if (distance_to_next_coordinate >= desired_length)
else
{
coordinates.resize(coordinate_index + 1);
const auto distance_between_last_coordinates =
util::coordinate_calculation::haversineDistance(*(coordinates.end() - 2),
*(coordinates.end() - 1));
const auto interpolation_factor = ComputeInterpolationFactor(
desired_length - length_cache.back(), 0, distance_between_last_coordinates);
coordinates.back() = util::coordinate_calculation::interpolateLinear(
ComputeInterpolationFactor(
desired_length, distance_to_current_coordinate, distance_to_next_coordinate),
coordinates[coordinate_index - 1],
coordinates[coordinate_index]);
break;
interpolation_factor, *(coordinates.end() - 2), coordinates.back());
return coordinates;
}
// remember the accumulated distance
distance_to_current_coordinate = distance_to_next_coordinate;
}
if (coordinates.size() > 2 &&
util::coordinate_calculation::haversineDistance(coordinates[0], coordinates[1]) <= 1)
coordinates.erase(coordinates.begin() + 1);
else
{
BOOST_ASSERT(!use_cache || length_cache.back() >= desired_length);
for (coordinate_index = 1; coordinate_index < coordinates.size(); ++coordinate_index)
{
// get the length to the next candidate, given that we can or cannot have a length cache
const auto distance_to_next_coordinate =
use_cache ? read_length_from_cache() : compute_length();
BOOST_ASSERT(coordinates.size());
return coordinates;
// if we reached the number of coordinates, we can stop here
if (distance_to_next_coordinate >= desired_length)
{
coordinates.resize(coordinate_index + 1);
coordinates.back() = util::coordinate_calculation::interpolateLinear(
ComputeInterpolationFactor(desired_length,
distance_to_current_coordinate,
distance_to_next_coordinate),
coordinates[coordinate_index - 1],
coordinates[coordinate_index]);
break;
}
// remember the accumulated distance
distance_to_current_coordinate = distance_to_next_coordinate;
}
BOOST_ASSERT(!coordinates.empty());
return coordinates;
}
}
util::Coordinate
@@ -768,6 +844,7 @@ std::vector<util::Coordinate>
CoordinateExtractor::TrimCoordinatesByLengthFront(std::vector<util::Coordinate> coordinates,
const double desired_length) const
{
BOOST_ASSERT(desired_length >= 0);
double distance_to_index = 0;
std::size_t index = 0;
for (std::size_t next_index = 1; next_index < coordinates.size(); ++next_index)