osrm-backend/routing_algorithms/tsp_brute_force.hpp
Chau Nguyen b15f8f68e4 refactor and improve the round trip computation of multiple SCCs
Problem:
- old solution was slow
- depending on the result of TarjanSCC, new distance tables and new phantom node vectors were created to run tsp on it

Solution:
- dont create new distance tables and phantom node vectors
- pass an additional vector with the information which locations are in the same component and ignore all others

fix bug for scc split computation
2015-09-01 15:20:33 +02:00

141 lines
5.5 KiB
C++

/*
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*/
#ifndef TSP_BRUTE_FORCE_HPP
#define TSP_BRUTE_FORCE_HPP
#include "../data_structures/search_engine.hpp"
#include "../util/string_util.hpp"
#include <osrm/json_container.hpp>
#include <cstdlib>
#include <algorithm>
#include <string>
#include <vector>
#include <limits>
#include <iostream>
#include "../util/simple_logger.hpp"
namespace osrm
{
namespace tsp
{
template <typename number>
int ReturnDistance(const std::vector<EdgeWeight> & dist_table, const std::vector<number> & location_order, const int min_route_dist, const int number_of_locations, const int component_size) {
int i = 0;
int route_dist = 0;
// compute length and stop if length is longer than route already found
while (i < component_size - 1 && route_dist < min_route_dist) {
//get distance from location i to location i+1
route_dist += *(dist_table.begin() + (location_order[i] * number_of_locations) + location_order[i+1]);
++i;
}
//get distance from last location to first location
route_dist += *(dist_table.begin() + (location_order[component_size-1] * number_of_locations) + location_order[0]);
if (route_dist < min_route_dist) {
return route_dist;
}
else {
return -1;
}
}
void BruteForceTSP(std::vector<unsigned> & location,
const PhantomNodeArray & phantom_node_vector,
const std::vector<EdgeWeight> & dist_table,
InternalRouteResult & min_route,
std::vector<int> & min_loc_permutation) {
const auto number_of_location = phantom_node_vector.size();
const int component_size = location.size();
int min_route_dist = std::numeric_limits<int>::max();
std::vector<unsigned> min_location;
// check length of all possible permutation of the location ids
do {
// int new_distance = ReturnDistance(dist_table, location, min_route_dist, number_of_location, component_size);
int new_distance = 4;
if (new_distance != -1) {
min_route_dist = new_distance;
min_location = location;
}
} while(std::next_permutation(location.begin(), location.end()));
PhantomNodes viapoint;
for (int i = 0; i < component_size - 1; ++i) {
viapoint = PhantomNodes{phantom_node_vector[min_location[i]][0], phantom_node_vector[min_location[i + 1]][0]};
min_route.segment_end_coordinates.emplace_back(viapoint);
min_loc_permutation[min_location[i]] = i;
}
min_loc_permutation[min_location[component_size - 1]] = component_size - 1;
viapoint = PhantomNodes{phantom_node_vector[min_location[component_size - 1]][0], phantom_node_vector[min_location[0]][0]};
min_route.segment_end_coordinates.emplace_back(viapoint);
}
void BruteForceTSP(const PhantomNodeArray & phantom_node_vector,
const std::vector<EdgeWeight> & dist_table,
InternalRouteResult & min_route,
std::vector<int> & min_loc_permutation) {
const auto number_of_locations = phantom_node_vector.size();
// fill a vector with node ids
std::vector<int> location_ids(number_of_locations);
std::iota(location_ids.begin(), location_ids.end(), 0);
int min_route_dist = std::numeric_limits<int>::max();
// check length of all possible permutation of the location ids
do {
int new_distance = ReturnDistance(dist_table, location_ids, min_route_dist, number_of_locations, number_of_locations);
if (new_distance != -1) {
min_route_dist = new_distance;
//TODO: this gets copied right? fix this
min_loc_permutation = location_ids;
}
} while(std::next_permutation(location_ids.begin(), location_ids.end()));
PhantomNodes viapoint;
for (int i = 0; i < number_of_locations - 1; ++i) {
viapoint = PhantomNodes{phantom_node_vector[min_loc_permutation[i]][0], phantom_node_vector[min_loc_permutation[i + 1]][0]};
min_route.segment_end_coordinates.emplace_back(viapoint);
}
viapoint = PhantomNodes{phantom_node_vector[min_loc_permutation[number_of_locations - 1]][0], phantom_node_vector[min_loc_permutation[0]][0]};
min_route.segment_end_coordinates.emplace_back(viapoint);
}
}
}
#endif // TSP_BRUTE_FORCE_HPP