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Trip with Fixed Start and End points (TFSE) (#3408)

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* fixed start and end trip feature to trip service
This commit is contained in:
Kajari Ghosh
2017-02-10 05:13:20 -05:00
committed by GitHub
parent 3e2db47cc8
commit 2218658969
15 changed files with 895 additions and 277 deletions
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src/engine/plugins/trip.cpp
+165 -146
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@@ -1,7 +1,5 @@
#include "engine/plugins/trip.hpp"
#include "extractor/tarjan_scc.hpp"
#include "engine/api/trip_api.hpp"
#include "engine/api/trip_parameters.hpp"
#include "engine/trip/trip_brute_force.hpp"
@@ -16,6 +14,7 @@
#include <algorithm>
#include <cstdlib>
#include <iterator>
#include <limits>
#include <memory>
#include <string>
#include <utility>
@@ -28,129 +27,150 @@ namespace engine
namespace plugins
{
// Object to hold all strongly connected components (scc) of a graph
// to access all graphs with component ID i, get the iterators by:
// auto start = std::begin(scc_component.component) + scc_component.range[i];
// auto end = std::begin(scc_component.component) + scc_component.range[i+1];
struct SCC_Component
bool IsStronglyConnectedComponent(const util::DistTableWrapper<EdgeWeight> &result_table)
{
// in_component: all NodeIDs sorted by component ID
// in_range: index where a new component starts
//
// example: NodeID 0, 1, 2, 4, 5 are in component 0
// NodeID 3, 6, 7, 8 are in component 1
// => in_component = [0, 1, 2, 4, 5, 3, 6, 7, 8]
// => in_range = [0, 5]
SCC_Component(std::vector<NodeID> in_component_nodes, std::vector<size_t> in_range)
: component(std::move(in_component_nodes)), range(std::move(in_range))
{
BOOST_ASSERT_MSG(component.size() > 0, "there's no scc component");
BOOST_ASSERT_MSG(*std::max_element(range.begin(), range.end()) == component.size(),
"scc component ranges are out of bound");
BOOST_ASSERT_MSG(*std::min_element(range.begin(), range.end()) == 0,
"invalid scc component range");
BOOST_ASSERT_MSG(std::is_sorted(std::begin(range), std::end(range)),
"invalid component ranges");
}
std::size_t GetNumberOfComponents() const
{
BOOST_ASSERT_MSG(range.size() > 0, "there's no range");
return range.size() - 1;
}
const std::vector<NodeID> component;
std::vector<std::size_t> range;
};
// takes the number of locations and its duration matrix,
// identifies and splits the graph in its strongly connected components (scc)
// and returns an SCC_Component
SCC_Component SplitUnaccessibleLocations(const std::size_t number_of_locations,
const util::DistTableWrapper<EdgeWeight> &result_table)
{
if (std::find(std::begin(result_table), std::end(result_table), INVALID_EDGE_WEIGHT) ==
std::end(result_table))
{
// whole graph is one scc
std::vector<NodeID> location_ids(number_of_locations);
std::iota(std::begin(location_ids), std::end(location_ids), 0);
std::vector<size_t> range = {0, location_ids.size()};
return SCC_Component(std::move(location_ids), std::move(range));
}
// Run TarjanSCC
auto wrapper = std::make_shared<util::MatrixGraphWrapper<EdgeWeight>>(result_table.GetTable(),
number_of_locations);
auto scc = extractor::TarjanSCC<util::MatrixGraphWrapper<EdgeWeight>>(wrapper);
scc.Run();
const auto number_of_components = scc.GetNumberOfComponents();
std::vector<std::size_t> range_insertion;
std::vector<std::size_t> range;
range_insertion.reserve(number_of_components);
range.reserve(number_of_components);
std::vector<NodeID> components(number_of_locations, 0);
std::size_t prefix = 0;
for (std::size_t j = 0; j < number_of_components; ++j)
{
range_insertion.push_back(prefix);
range.push_back(prefix);
prefix += scc.GetComponentSize(j);
}
// senitel
range.push_back(components.size());
for (std::size_t i = 0; i < number_of_locations; ++i)
{
components[range_insertion[scc.GetComponentID(i)]] = i;
++range_insertion[scc.GetComponentID(i)];
}
return SCC_Component(std::move(components), std::move(range));
return std::find(std::begin(result_table), std::end(result_table), INVALID_EDGE_WEIGHT) ==
std::end(result_table);
}
bool IsSupportedParameterCombination(const bool fixed_start,
const bool fixed_end,
const bool roundtrip)
{
if (fixed_start && fixed_end && !roundtrip)
{
return true;
}
else if (roundtrip)
{
return true;
}
else
{
return false;
}
}
// given the node order in which to visit, compute the actual route (with geometry, travel time and
// so on) and return the result
InternalRouteResult
TripPlugin::ComputeRoute(const std::shared_ptr<const datafacade::BaseDataFacade> facade,
const std::vector<PhantomNode> &snapped_phantoms,
const std::vector<NodeID> &trip) const
const std::vector<NodeID> &trip,
const bool roundtrip) const
{
InternalRouteResult min_route;
// given he final trip, compute total duration and return the route and location permutation
// given the final trip, compute total duration and return the route and location permutation
PhantomNodes viapoint;
const auto start = std::begin(trip);
const auto end = std::end(trip);
// computes a roundtrip from the nodes in trip
for (auto it = start; it != end; ++it)
for (auto node = trip.begin(); node < trip.end() - 1; ++node)
{
const auto from_node = *it;
// if from_node is the last node, compute the route from the last to the first location
const auto to_node = std::next(it) != end ? *std::next(it) : *start;
const auto from_node = *node;
const auto to_node = *std::next(node);
viapoint = PhantomNodes{snapped_phantoms[from_node], snapped_phantoms[to_node]};
min_route.segment_end_coordinates.emplace_back(viapoint);
}
BOOST_ASSERT(min_route.segment_end_coordinates.size() == trip.size());
// return back to the first node if it is a round trip
if (roundtrip)
{
viapoint = PhantomNodes{snapped_phantoms[trip.back()], snapped_phantoms[trip.front()]};
min_route.segment_end_coordinates.emplace_back(viapoint);
// trip comes out to be something like 0 1 4 3 2 0
BOOST_ASSERT(min_route.segment_end_coordinates.size() == trip.size());
}
else
{
// trip comes out to be something like 0 1 4 3 2, so the sizes don't match
BOOST_ASSERT(min_route.segment_end_coordinates.size() == trip.size() - 1);
}
shortest_path(facade, min_route.segment_end_coordinates, {false}, min_route);
BOOST_ASSERT_MSG(min_route.shortest_path_length < INVALID_EDGE_WEIGHT, "unroutable route");
return min_route;
}
void ManipulateTableForFSE(const std::size_t source_id,
const std::size_t destination_id,
util::DistTableWrapper<EdgeWeight> &result_table)
{
// ****************** Change Table *************************
// The following code manipulates the table and produces the new table for
// Trip with Fixed Start and End (TFSE). In the example the source is a
// and destination is c. The new table forces the roundtrip to start at
// source and end at destination by virtually squashing them together.
// This way the brute force and the farthest insertion algorithms don't
// have to be modified, and instead we can just pass a modified table to
// return a non-roundtrip "optimal" route from a start node to an end node.
// Original Table // New Table
// a b c d e // a b c d e
// a 0 15 36 34 30 // a 0 15 10000 34 30
// b 15 0 25 30 34 // b 10000 0 25 30 34
// c 36 25 0 18 32 // c 0 10000 0 10000 10000
// d 34 30 18 0 15 // d 10000 30 18 0 15
// e 30 34 32 15 0 // e 10000 34 32 15 0
// change parameters.source column
// set any node to source to impossibly high numbers so it will never
// try to use any node->source in the middle of the "optimal path"
for (std::size_t i = 0; i < result_table.GetNumberOfNodes(); i++)
{
if (i == source_id)
continue;
result_table.SetValue(i, source_id, INVALID_EDGE_WEIGHT);
}
// change parameters.destination row
// set destination to anywhere else to impossibly high numbers so it will
// never try to use destination->any node in the middle of the "optimal path"
for (std::size_t i = 0; i < result_table.GetNumberOfNodes(); i++)
{
if (i == destination_id)
continue;
result_table.SetValue(destination_id, i, INVALID_EDGE_WEIGHT);
}
// set destination->source to zero so rountrip treats source and
// destination as one location
result_table.SetValue(destination_id, source_id, 0);
// set source->destination as very high number so algorithm is forced
// to find another path to get to destination
result_table.SetValue(source_id, destination_id, INVALID_EDGE_WEIGHT);
//********* End of changes to table *************************************
}
Status TripPlugin::HandleRequest(const std::shared_ptr<const datafacade::BaseDataFacade> facade,
const api::TripParameters &parameters,
util::json::Object &json_result) const
{
BOOST_ASSERT(parameters.IsValid());
const auto number_of_locations = parameters.coordinates.size();
std::size_t source_id = INVALID_INDEX;
std::size_t destination_id = INVALID_INDEX;
if (parameters.source == api::TripParameters::SourceType::First)
{
source_id = 0;
}
if (parameters.destination == api::TripParameters::DestinationType::Last)
{
BOOST_ASSERT(number_of_locations > 0);
destination_id = number_of_locations - 1;
}
bool fixed_start = (source_id == 0);
bool fixed_end = (destination_id == number_of_locations - 1);
if (!IsSupportedParameterCombination(fixed_start, fixed_end, parameters.roundtrip))
{
return Error("NotImplemented", "This request is not supported", json_result);
}
// enforce maximum number of locations for performance reasons
if (max_locations_trip > 0 &&
static_cast<int>(parameters.coordinates.size()) > max_locations_trip)
if (max_locations_trip > 0 && static_cast<int>(number_of_locations) > max_locations_trip)
{
return Error("TooBig", "Too many trip coordinates", json_result);
}
@@ -161,21 +181,27 @@ Status TripPlugin::HandleRequest(const std::shared_ptr<const datafacade::BaseDat
}
auto phantom_node_pairs = GetPhantomNodes(*facade, parameters);
if (phantom_node_pairs.size() != parameters.coordinates.size())
if (phantom_node_pairs.size() != number_of_locations)
{
return Error("NoSegment",
std::string("Could not find a matching segment for coordinate ") +
std::to_string(phantom_node_pairs.size()),
json_result);
}
BOOST_ASSERT(phantom_node_pairs.size() == parameters.coordinates.size());
BOOST_ASSERT(phantom_node_pairs.size() == number_of_locations);
if (fixed_start && fixed_end && (source_id >= parameters.coordinates.size() ||
destination_id >= parameters.coordinates.size()))
{
return Error("InvalidValue", "Invalid source or destination value.", json_result);
}
auto snapped_phantoms = SnapPhantomNodes(phantom_node_pairs);
const auto number_of_locations = snapped_phantoms.size();
BOOST_ASSERT(snapped_phantoms.size() == number_of_locations);
// compute the duration table of all phantom nodes
const auto result_table = util::DistTableWrapper<EdgeWeight>(
auto result_table = util::DistTableWrapper<EdgeWeight>(
duration_table(facade, snapped_phantoms, {}, {}), number_of_locations);
if (result_table.size() == 0)
@@ -187,56 +213,49 @@ Status TripPlugin::HandleRequest(const std::shared_ptr<const datafacade::BaseDat
BOOST_ASSERT_MSG(result_table.size() == number_of_locations * number_of_locations,
"Distance Table has wrong size");
// get scc components
SCC_Component scc = SplitUnaccessibleLocations(number_of_locations, result_table);
std::vector<std::vector<NodeID>> trips;
trips.reserve(scc.GetNumberOfComponents());
// run Trip computation for every SCC
for (std::size_t k = 0; k < scc.GetNumberOfComponents(); ++k)
if (!IsStronglyConnectedComponent(result_table))
{
const auto component_size = scc.range[k + 1] - scc.range[k];
BOOST_ASSERT_MSG(component_size > 0, "invalid component size");
std::vector<NodeID> scc_route;
auto route_begin = std::begin(scc.component) + scc.range[k];
auto route_end = std::begin(scc.component) + scc.range[k + 1];
if (component_size > 1)
{
if (component_size < BF_MAX_FEASABLE)
{
scc_route =
trip::BruteForceTrip(route_begin, route_end, number_of_locations, result_table);
}
else
{
scc_route = trip::FarthestInsertionTrip(
route_begin, route_end, number_of_locations, result_table);
}
}
else
{
scc_route = std::vector<NodeID>(route_begin, route_end);
}
trips.push_back(std::move(scc_route));
}
if (trips.empty())
{
return Error("NoTrips", "Cannot find trips", json_result);
return Error("NoTrips", "No trip visiting all destinations possible.", json_result);
}
// compute all round trip routes
std::vector<InternalRouteResult> routes;
routes.reserve(trips.size());
for (const auto &trip : trips)
if (fixed_start && fixed_end)
{
routes.push_back(ComputeRoute(facade, snapped_phantoms, trip));
ManipulateTableForFSE(source_id, destination_id, result_table);
}
std::vector<NodeID> trip;
trip.reserve(number_of_locations);
// get an optimized order in which the destinations should be visited
if (number_of_locations < BF_MAX_FEASABLE)
{
trip = trip::BruteForceTrip(number_of_locations, result_table);
}
else
{
trip = trip::FarthestInsertionTrip(number_of_locations, result_table);
}
// rotate result such that roundtrip starts at node with index 0
// thist first if covers scenarios: !fixed_end || fixed_start || (fixed_start && fixed_end)
if (!fixed_end || fixed_start)
{
auto desired_start_index = std::find(std::begin(trip), std::end(trip), 0);
BOOST_ASSERT(desired_start_index != std::end(trip));
std::rotate(std::begin(trip), desired_start_index, std::end(trip));
}
else if (fixed_end && !fixed_start && parameters.roundtrip)
{
auto desired_start_index = std::find(std::begin(trip), std::end(trip), destination_id);
BOOST_ASSERT(desired_start_index != std::end(trip));
std::rotate(std::begin(trip), desired_start_index, std::end(trip));
}
// get the route when visiting all destinations in optimized order
InternalRouteResult route = ComputeRoute(facade, snapped_phantoms, trip, parameters.roundtrip);
// get api response
const std::vector<std::vector<NodeID>> trips = {trip};
const std::vector<InternalRouteResult> routes = {route};
api::TripAPI trip_api{*facade, parameters};
trip_api.MakeResponse(trips, routes, snapped_phantoms, json_result);
@@ -244,4 +263,4 @@ Status TripPlugin::HandleRequest(const std::shared_ptr<const datafacade::BaseDat
}
}
}
}
}