198 lines
8.1 KiB
C++
198 lines
8.1 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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// 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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using NodeIDIter = typename std::vector<NodeID>::iterator;
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std::pair<EdgeWeight, NodeIDIter> GetShortestRoundTrip(const NodeID new_loc,
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const DistTableWrapper<EdgeWeight> & dist_table,
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const std::size_t 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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NodeIDIter 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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BOOST_ASSERT_MSG(dist_from != INVALID_EDGE_WEIGHT,
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"distance has invalid edge weight");
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BOOST_ASSERT_MSG(dist_to != INVALID_EDGE_WEIGHT,
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"distance has invalid edge weight");
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BOOST_ASSERT_MSG(trip_dist >= 0,
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"previous trip was not minimal. something's wrong");
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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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BOOST_ASSERT_MSG(min_trip_distance != INVALID_EDGE_WEIGHT,
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"trip has invalid edge weight");
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return std::make_pair(min_trip_distance, next_insert_point_candidate);
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}
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template <typename NodeIDIterator>
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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 & component_size,
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const NodeIDIterator & start,
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const NodeIDIterator & end,
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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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BOOST_ASSERT_MSG(number_of_locations >= component_size,
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"component size bigger than total number of locations");
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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 (std::size_t j = 2; j < component_size; ++j) {
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auto farthest_distance = 0;
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auto next_node = -1;
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NodeIDIter 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 = start; i != end; ++i) {
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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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BOOST_ASSERT_MSG(insert_candidate.first != INVALID_EDGE_WEIGHT,
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"shortest round trip is invalid");
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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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BOOST_ASSERT_MSG(next_node >= 0, "next node to visit is invalid");
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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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template <typename NodeIDIterator>
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std::vector<NodeID> FarthestInsertionTSP(const NodeIDIterator & start,
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const NodeIDIterator & end,
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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 component_size = std::distance(start, end);
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auto max_from = -1;
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auto max_to = -1;
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if (component_size == 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(std::begin(dist_table), std::max_element(std::begin(dist_table), std::end(dist_table)));
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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 = start; x != end; ++x) {
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for (auto y = start; y != end; ++y) {
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const 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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BOOST_ASSERT_MSG(max_from < number_of_locations && max_from >= 0, "start node");
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BOOST_ASSERT_MSG(max_to < number_of_locations && max_to >= 0, "start node");
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return FindRoute(number_of_locations, component_size, start, end, dist_table, max_from, max_to);
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}
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} //end namespace tsp
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} //end namespace osrm
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#endif // TSP_FARTHEST_INSERTION_HPP
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