027f5cc3f8
C++: - [Up] linear_programming - [Up] integer_programming - constraint_programming_CP / rabbits_pheasants_cp - knapsack - max_flow / min_cost_flow - tsp / vrp note: previous "fuzzy" tsp has been renamed random_tsp. .Net: - vrp
89 lines
2.8 KiB
C++
89 lines
2.8 KiB
C++
// Copyright 2018 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.
|
|
|
|
#include "ortools/base/logging.h"
|
|
#include "ortools/graph/min_cost_flow.h"
|
|
|
|
namespace operations_research {
|
|
struct Arc {
|
|
std::pair<NodeIndex, NodeIndex> nodes;
|
|
FlowQuantity capacity;
|
|
FlowQuantity unit_cost;
|
|
};
|
|
|
|
void SolveMinCostFlow() {
|
|
// Define supply of each node.
|
|
const std::vector<std::pair<NodeIndex, FlowQuantity>> supplies = {
|
|
{0, 20},
|
|
{1, 0},
|
|
{2, 0},
|
|
{3,-5},
|
|
{4,-15}
|
|
};
|
|
|
|
// Define each arc
|
|
// Can't use std::tuple<NodeIndex, NodeIndex, FlowQuantity>
|
|
// Initialization list is not working on std:tuple cf. N4387
|
|
// Arc are stored as {{begin_node, end_node}, capacity}
|
|
const std::vector<Arc> arcs = {
|
|
{{0, 1}, 15, 4},
|
|
{{0, 2}, 8, 4},
|
|
{{1, 2}, 20, 2},
|
|
{{1, 3}, 4, 2},
|
|
{{1, 4}, 10, 6},
|
|
{{2, 3}, 15, 1},
|
|
{{2, 4}, 4, 3},
|
|
{{3, 4}, 20, 2},
|
|
{{4, 2}, 5, 3}
|
|
};
|
|
|
|
StarGraph graph(supplies.size(), arcs.size());
|
|
MinCostFlow min_cost_flow(&graph);
|
|
for (const auto &it : arcs) {
|
|
ArcIndex arc = graph.AddArc(it.nodes.first, it.nodes.second);
|
|
min_cost_flow.SetArcCapacity(arc, it.capacity);
|
|
min_cost_flow.SetArcUnitCost(arc, it.unit_cost);
|
|
}
|
|
for (const auto &it : supplies) {
|
|
min_cost_flow.SetNodeSupply(it.first, it.second);
|
|
}
|
|
|
|
LOG(INFO) << "Solving min cost flow with: "
|
|
<< graph.num_nodes() << " nodes, and "
|
|
<< graph.num_arcs() << " arcs.";
|
|
|
|
// Find the maximum flow between node 0 and node 4.
|
|
min_cost_flow.Solve();
|
|
if (MinCostFlow::OPTIMAL != min_cost_flow.status()) {
|
|
LOG(FATAL) << "Solving the max flow is not optimal!";
|
|
}
|
|
FlowQuantity total_flow_cost = min_cost_flow.GetOptimalCost();
|
|
LOG(INFO) << "Minimum cost flow: " << total_flow_cost;
|
|
LOG(INFO) << "";
|
|
LOG(INFO) << "Arc : Flow / Capacity / Cost";
|
|
for (int i = 0; i < arcs.size(); ++i) {
|
|
LOG(INFO)
|
|
<< graph.Tail(i) << " -> " << graph.Head(i) << ": "
|
|
<< min_cost_flow.Flow(i) << " / " << min_cost_flow.Capacity(i)
|
|
<< " / " << min_cost_flow.UnitCost(i);
|
|
}
|
|
}
|
|
} // namespace operations_research
|
|
|
|
int main(int argc, char** argv) {
|
|
google::InitGoogleLogging(argv[0]);
|
|
FLAGS_logtostderr = 1;
|
|
operations_research::SolveMinCostFlow();
|
|
return 0;
|
|
}
|