vrp_solution_callback.cc

// Copyright 2010-2024 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// [START program]
// [START import]
#include <cstdint>
#include <functional>
#include <sstream>
#include <string>
#include <vector>

#include "google/protobuf/duration.pb.h"
#include "ortools/constraint_solver/routing.h"
#include "ortools/constraint_solver/routing_enums.pb.h"
#include "ortools/constraint_solver/routing_index_manager.h"
#include "ortools/constraint_solver/routing_parameters.h"
// [END import]

namespace operations_research {
// [START data_model]
struct DataModel {
  const std::vector<std::vector<int64_t>> distance_matrix{
      {0, 548, 776, 696, 582, 274, 502, 194, 308, 194, 536, 502, 388, 354, 468,
       776, 662},
      {548, 0, 684, 308, 194, 502, 730, 354, 696, 742, 1084, 594, 480, 674,
       1016, 868, 1210},
      {776, 684, 0, 992, 878, 502, 274, 810, 468, 742, 400, 1278, 1164, 1130,
       788, 1552, 754},
      {696, 308, 992, 0, 114, 650, 878, 502, 844, 890, 1232, 514, 628, 822,
       1164, 560, 1358},
      {582, 194, 878, 114, 0, 536, 764, 388, 730, 776, 1118, 400, 514, 708,
       1050, 674, 1244},
      {274, 502, 502, 650, 536, 0, 228, 308, 194, 240, 582, 776, 662, 628, 514,
       1050, 708},
      {502, 730, 274, 878, 764, 228, 0, 536, 194, 468, 354, 1004, 890, 856, 514,
       1278, 480},
      {194, 354, 810, 502, 388, 308, 536, 0, 342, 388, 730, 468, 354, 320, 662,
       742, 856},
      {308, 696, 468, 844, 730, 194, 194, 342, 0, 274, 388, 810, 696, 662, 320,
       1084, 514},
      {194, 742, 742, 890, 776, 240, 468, 388, 274, 0, 342, 536, 422, 388, 274,
       810, 468},
      {536, 1084, 400, 1232, 1118, 582, 354, 730, 388, 342, 0, 878, 764, 730,
       388, 1152, 354},
      {502, 594, 1278, 514, 400, 776, 1004, 468, 810, 536, 878, 0, 114, 308,
       650, 274, 844},
      {388, 480, 1164, 628, 514, 662, 890, 354, 696, 422, 764, 114, 0, 194, 536,
       388, 730},
      {354, 674, 1130, 822, 708, 628, 856, 320, 662, 388, 730, 308, 194, 0, 342,
       422, 536},
      {468, 1016, 788, 1164, 1050, 514, 514, 662, 320, 274, 388, 650, 536, 342,
       0, 764, 194},
      {776, 868, 1552, 560, 674, 1050, 1278, 742, 1084, 810, 1152, 274, 388,
       422, 764, 0, 798},
      {662, 1210, 754, 1358, 1244, 708, 480, 856, 514, 468, 354, 844, 730, 536,
       194, 798, 0},
  };
  const int num_vehicles = 4;
  const RoutingIndexManager::NodeIndex depot{0};
};
// [END data_model]

//! @brief Print the solution.
//! @param[in] routing_manager Index manager used.
//! @param[in] routing_model Routing solver used.
// [START solution_callback_printer]
void print_solution(const RoutingIndexManager& routing_manager,
                    const RoutingModel& routing_model) {
  LOG(INFO) << "################";
  LOG(INFO) << "Solution objective: " << routing_model.CostVar()->Value();
  int64_t total_distance = 0;
  for (int vehicle_id = 0; vehicle_id < routing_manager.num_vehicles();
       ++vehicle_id) {
    int64_t index = routing_model.Start(vehicle_id);
    LOG(INFO) << "Route for Vehicle " << vehicle_id << ":";
    int64_t route_distance = 0;
    std::stringstream route;
    while (!routing_model.IsEnd(index)) {
      route << " " << routing_manager.IndexToNode(index).value() << " ->";
      const int64_t previous_index = index;
      index = routing_model.NextVar(index)->Value();
      route_distance += routing_model.GetArcCostForVehicle(
          previous_index, index, int64_t{vehicle_id});
    }
    LOG(INFO) << route.str() << routing_manager.IndexToNode(index).value();
    LOG(INFO) << "Distance of the route: " << route_distance << "m";
    total_distance += route_distance;
  }
  LOG(INFO) << "Total distance of all routes: " << total_distance << "m";
}
// [END solution_callback_printer]

// [START solution_callback]
struct SolutionCallback {
  const RoutingIndexManager& routing_manager;
  const RoutingModel& routing_model;
  const int64_t max_solution;

  SolutionCallback(const RoutingIndexManager& manager,
                   const RoutingModel& model, const int64_t max_solution)
      : routing_manager(manager),
        routing_model(model),
        max_solution(max_solution) {
    objectives.reserve(max_solution);
  }
  ~SolutionCallback() {}

  void Run() {
    const int64_t objective = routing_model.CostVar()->Value();
    if (objectives.empty() || objective < objectives.back()) {
      objectives.push_back(objective);
      print_solution(routing_manager, routing_model);
      counter++;
    }
    if (counter >= max_solution) {
      routing_model.solver()->FinishCurrentSearch();
    }
  }

  std::vector<int64_t> objectives{};

 private:
  int64_t counter = 0;
};
// [END solution_callback]

void VrpSolutionCallback() {
  // Instantiate the data problem.
  // [START data]
  DataModel data;
  // [END data]

  // Create Routing Index Manager.
  // [START index_manager]
  RoutingIndexManager routing_manager(data.distance_matrix.size(),
                                      data.num_vehicles, data.depot);
  // [END index_manager]

  // Create Routing Model.
  // [START routing_model]
  RoutingModel routing_model(routing_manager);
  // [END routing_model]

  // Create and register a transit callback.
  // [START transit_callback]
  const int transit_callback_index = routing_model.RegisterTransitCallback(
      [&data, &routing_manager](const int64_t from_index,
                                const int64_t to_index) -> int64_t {
        // Convert from routing variable Index to distance matrix NodeIndex.
        const int from_node = routing_manager.IndexToNode(from_index).value();
        const int to_node = routing_manager.IndexToNode(to_index).value();
        return data.distance_matrix[from_node][to_node];
      });
  // [END transit_callback]

  // Define cost of each arc.
  // [START arc_cost]
  routing_model.SetArcCostEvaluatorOfAllVehicles(transit_callback_index);
  // [END arc_cost]

  // Add Distance constraint.
  // [START distance_constraint]
  routing_model.AddDimension(transit_callback_index,
                             0,     // no slack
                             3000,  // vehicle maximum travel distance
                             true,  // start cumul to zero
                             "Distance");
  routing_model.GetMutableDimension("Distance")
      ->SetGlobalSpanCostCoefficient(100);
  // [END distance_constraint]

  // Attach a solution callback.
  // [START attach_callback]
  SolutionCallback solution_callback{routing_manager, routing_model,
                                     /*max_solution=*/15};
  routing_model.AddAtSolutionCallback(
      std::bind(&SolutionCallback::Run, &solution_callback));
  // [END attach_callback]

  // Setting first solution heuristic.
  // [START parameters]
  RoutingSearchParameters search_parameters = DefaultRoutingSearchParameters();
  search_parameters.set_first_solution_strategy(
      FirstSolutionStrategy::PATH_CHEAPEST_ARC);
  search_parameters.set_local_search_metaheuristic(
      LocalSearchMetaheuristic::GUIDED_LOCAL_SEARCH);
  search_parameters.mutable_time_limit()->set_seconds(5);
  // [END parameters]

  // Solve the problem.
  // [START solve]
  const Assignment* solution =
      routing_model.SolveWithParameters(search_parameters);
  // [END solve]

  // Print solution on console.
  // [START print_solution]
  if (solution != nullptr) {
    LOG(INFO) << "Best objectives: "
              << std::to_string(solution_callback.objectives.back());
  } else {
    LOG(INFO) << "No solution found.";
  }
  // [END print_solution]
}
}  // namespace operations_research

int main(int /*argc*/, char* /*argv*/[]) {
  operations_research::VrpSolutionCallback();
  return EXIT_SUCCESS;
}
// [END program]