234 lines
9.6 KiB
C++
234 lines
9.6 KiB
C++
/*
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Copyright (c) 2015, Project OSRM contributors
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All rights reserved.
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this list
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of conditions and the following disclaimer.
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Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or
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other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
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ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TSP_FARTHEST_INSERTION_HPP
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#define TSP_FARTHEST_INSERTION_HPP
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#include "../data_structures/search_engine.hpp"
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#include "../util/string_util.hpp"
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#include "../util/dist_table_wrapper.hpp"
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#include "../tools/tsp_logs.hpp"
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#include <osrm/json_container.hpp>
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#include <cstdlib>
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#include <algorithm>
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#include <string>
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#include <vector>
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#include <limits>
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#include <iostream>
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namespace osrm
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{
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namespace tsp
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{
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using NodeIterator = typename std::vector<NodeID>::iterator;
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// given a route and a new location, find the best place of insertion and
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// check the distance of roundtrip when the new location is additionally visited
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std::pair<EdgeWeight, NodeIterator> GetShortestRoundTrip(const int new_loc,
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const DistTableWrapper<EdgeWeight> & dist_table,
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const int number_of_locations,
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std::vector<NodeID> & route){
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auto min_trip_distance = INVALID_EDGE_WEIGHT;
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NodeIterator next_insert_point_candidate;
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// for all nodes in the current trip find the best insertion resulting in the shortest path
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// assert min 2 nodes in route
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for (auto from_node = std::begin(route); from_node != std::end(route); ++from_node) {
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auto to_node = std::next(from_node);
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if (to_node == std::end(route)) {
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to_node = std::begin(route);
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}
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const auto dist_from = dist_table(*from_node, new_loc);
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const auto dist_to = dist_table(new_loc, *to_node);
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const auto trip_dist = dist_from + dist_to - dist_table(*from_node, *to_node);;
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// from all possible insertions to the current trip, choose the shortest of all insertions
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if (trip_dist < min_trip_distance) {
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min_trip_distance = trip_dist;
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next_insert_point_candidate = to_node;
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}
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}
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return std::make_pair(min_trip_distance, next_insert_point_candidate);
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}
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// given two initial start nodes, find a roundtrip route using the farthest insertion algorithm
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std::vector<NodeID> FindRoute(const std::size_t & number_of_locations,
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const std::size_t & size_of_component,
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const std::vector<NodeID> & locations,
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const DistTableWrapper<EdgeWeight> & dist_table,
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const NodeID & start1,
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const NodeID & start2) {
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std::vector<NodeID> route;
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route.reserve(number_of_locations);
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// tracks which nodes have been already visited
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std::vector<bool> visited(number_of_locations, false);
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visited[start1] = true;
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visited[start2] = true;
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route.push_back(start1);
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route.push_back(start2);
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// add all other nodes missing (two nodes are already in the initial start trip)
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for (int j = 2; j < size_of_component; ++j) {
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auto farthest_distance = 0;
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auto next_node = -1;
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NodeIterator next_insert_point;
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// find unvisited loc i that is the farthest away from all other visited locs
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for (auto i : locations) {
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// find the shortest distance from i to all visited nodes
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if (!visited[i]) {
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auto insert_candidate = GetShortestRoundTrip(i, dist_table, number_of_locations, route);
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// add the location to the current trip such that it results in the shortest total tour
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if (insert_candidate.first >= farthest_distance) {
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farthest_distance = insert_candidate.first;
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next_node = i;
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next_insert_point = insert_candidate.second;
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}
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}
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}
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// mark as visited and insert node
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visited[next_node] = true;
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route.insert(next_insert_point, next_node);
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}
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return route;
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}
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std::vector<NodeID> FarthestInsertionTSP(const std::vector<NodeID> & locations,
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const std::size_t number_of_locations,
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const DistTableWrapper<EdgeWeight> & dist_table) {
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//////////////////////////////////////////////////////////////////////////////////////////////////
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// START FARTHEST INSERTION HERE
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// 1. start at a random round trip of 2 locations
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// 2. find the location that is the farthest away from the visited locations and whose insertion will make the round trip the longest
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// 3. add the found location to the current round trip such that round trip is the shortest
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// 4. repeat 2-3 until all locations are visited
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// 5. DONE!
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//////////////////////////////////////////////////////////////////////////////////////////////////
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const auto size_of_component = locations.size();
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auto max_from = -1;
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auto max_to = -1;
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if (size_of_component == number_of_locations) {
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// find the pair of location with the biggest distance and make the pair the initial start trip
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const auto index = std::distance(dist_table.begin(), std::max_element(dist_table.begin(), dist_table.end()));
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max_from = index / number_of_locations;
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max_to = index % number_of_locations;
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} else {
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auto max_dist = 0;
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for (auto x : locations) {
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for (auto y : locations) {
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auto xy_dist = dist_table(x, y);
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if (xy_dist > max_dist) {
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max_dist = xy_dist;
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max_from = x;
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max_to = y;
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}
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}
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}
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}
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return FindRoute(number_of_locations, size_of_component, locations, dist_table, max_from, max_to);
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}
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// std::vector<NodeID> FarthestInsertionTSP(const std::size_t number_of_locations,
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// const std::vector<EdgeWeight> & dist_table) {
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// //////////////////////////////////////////////////////////////////////////////////////////////////
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// // START FARTHEST INSERTION HERE
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// // 1. start at a random round trip of 2 locations
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// // 2. find the location that is the farthest away from the visited locations and whose insertion will make the round trip the longest
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// // 3. add the found location to the current round trip such that round trip is the shortest
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// // 4. repeat 2-3 until all locations are visited
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// // 5. DONE!
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// //////////////////////////////////////////////////////////////////////////////////////////////////
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// std::vector<NodeID> route;
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// route.reserve(number_of_locations);
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// // tracks which nodes have been already visited
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// std::vector<bool> visited(number_of_locations, false);
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// // find the pair of location with the biggest distance and make the pair the initial start trip
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// const auto index = std::distance(dist_table.begin(), std::max_element(dist_table.begin(), dist_table.end()));
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// const int max_from = index / number_of_locations;
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// const int max_to = index % number_of_locations;
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// visited[max_from] = true;
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// visited[max_to] = true;
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// route.push_back(max_from);
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// route.push_back(max_to);
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// // add all other nodes missing (two nodes are already in the initial start trip)
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// for (int j = 2; j < number_of_locations; ++j) {
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// auto farthest_distance = 0;
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// auto next_node = -1;
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// //todo move out of loop and overwrite
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// NodeIterator next_insert_point;
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// // find unvisited loc i that is the farthest away from all other visited locs
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// for (int i = 0; i < number_of_locations; ++i) {
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// if (!visited[i]) {
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// auto min_trip_distance = INVALID_EDGE_WEIGHT;
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// NodeIterator next_insert_point_candidate;
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// GetShortestRoundTrip(i, dist_table, number_of_locations, route, min_trip_distance, next_insert_point_candidate);
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// // add the location to the current trip such that it results in the shortest total tour
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// if (min_trip_distance >= farthest_distance) {
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// farthest_distance = min_trip_distance;
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// next_node = i;
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// next_insert_point = next_insert_point_candidate;
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// }
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// }
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// }
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// // mark as visited and insert node
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// visited[next_node] = true;
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// route.insert(next_insert_point, next_node);
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// }
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// return route;
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// }
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} //end namespace osrm
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} //end namespace tsp
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#endif // TSP_FARTHEST_INSERTION_HPP
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