diff --git a/examples/contrib/vrptw_fixed_penalty.cs b/examples/contrib/vrptw_fixed_penalty.cs
new file mode 100644
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+++ b/examples/contrib/vrptw_fixed_penalty.cs
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+// Copyright 2021 Owen Lacey
+//
+// 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.
+
+using System;
+using Google.OrTools.ConstraintSolver;
+
+///
+/// Vehicles Routing Problem (VRP) with Time Windows, with the difference that we'll add a fixed penalty for lateness, as opposed to a linear penalty based on how late it is.
+/// Example is inspired by scheduling items which have contractual deadlines.
+/// Code based on https://developers.google.com/optimization/routing/vrptw#program
+///
+public class VrpTimeWindowFixedPenalty
+{
+ class DataModel
+ {
+ public long[,] TimeMatrix = {
+ { 0, 6, 9, 8, 7, 3, 6, 2, 3, 2, 6, 6, 4, 4, 5, 9, 7 },
+ { 6, 0, 8, 3, 2, 6, 8, 4, 8, 8, 13, 7, 5, 8, 12, 10, 14 },
+ { 9, 8, 0, 11, 10, 6, 3, 9, 5, 8, 4, 15, 14, 13, 9, 18, 9 },
+ { 8, 3, 11, 0, 1, 7, 10, 6, 10, 10, 14, 6, 7, 9, 14, 6, 16 },
+ { 7, 2, 10, 1, 0, 6, 9, 4, 8, 9, 13, 4, 6, 8, 12, 8, 14 },
+ { 3, 6, 6, 7, 6, 0, 2, 3, 2, 2, 7, 9, 7, 7, 6, 12, 8 },
+ { 6, 8, 3, 10, 9, 2, 0, 6, 2, 5, 4, 12, 10, 10, 6, 15, 5 },
+ { 2, 4, 9, 6, 4, 3, 6, 0, 4, 4, 8, 5, 4, 3, 7, 8, 10 },
+ { 3, 8, 5, 10, 8, 2, 2, 4, 0, 3, 4, 9, 8, 7, 3, 13, 6 },
+ { 2, 8, 8, 10, 9, 2, 5, 4, 3, 0, 4, 6, 5, 4, 3, 9, 5 },
+ { 6, 13, 4, 14, 13, 7, 4, 8, 4, 4, 0, 10, 9, 8, 4, 13, 4 },
+ { 6, 7, 15, 6, 4, 9, 12, 5, 9, 6, 10, 0, 1, 3, 7, 3, 10 },
+ { 4, 5, 14, 7, 6, 7, 10, 4, 8, 5, 9, 1, 0, 2, 6, 4, 8 },
+ { 4, 8, 13, 9, 8, 7, 10, 3, 7, 4, 8, 3, 2, 0, 4, 5, 6 },
+ { 5, 12, 9, 14, 12, 6, 6, 7, 3, 3, 4, 7, 6, 4, 0, 9, 2 },
+ { 9, 10, 18, 6, 8, 12, 15, 8, 13, 9, 13, 3, 4, 5, 9, 0, 9 },
+ { 7, 14, 9, 16, 14, 8, 5, 10, 6, 5, 4, 10, 8, 6, 2, 9, 0 },
+ };
+ public long[,] TimeWindows = {
+ { 0, 5 }, // depot
+ { 7, 12 }, // 1
+ { 10, 15 }, // 2
+ { 16, 18 }, // 3
+ { 10, 13 }, // 4
+ { 0, 5 }, // 5
+ { 5, 10 }, // 6
+ { 0, 4 }, // 7
+ { 5, 10 }, // 8
+ { 0, 3 }, // 9
+ { 10, 16 }, // 10
+ { 10, 15 }, // 11
+ { 0, 5 }, // 12
+ { 5, 10 }, // 13
+ { 7, 8 }, // 14
+ { 10, 15 }, // 15
+ { 11, 15 }, // 16
+ };
+ public int VehicleNumber = 4;
+ public int Depot = 0;
+ };
+
+ ///
+ /// Print the solution.
+ ///
+ static void PrintSolution(in DataModel data, in RoutingModel routing, in RoutingIndexManager manager,
+ in Assignment solution)
+ {
+ RoutingDimension timeDimension = routing.GetMutableDimension("Time");
+ // Inspect solution.
+ long totalTime = 0;
+ for (int i = 0; i < data.VehicleNumber; ++i)
+ {
+ Console.WriteLine("Route for Vehicle {0}:", i);
+ var index = routing.Start(i);
+ while (routing.IsEnd(index) == false)
+ {
+ var timeVar = timeDimension.CumulVar(index);
+ Console.Write("{0} Time({1},{2}) -> ", manager.IndexToNode(index), solution.Min(timeVar),
+ solution.Max(timeVar));
+ index = solution.Value(routing.NextVar(index));
+ }
+ var endTimeVar = timeDimension.CumulVar(index);
+ Console.WriteLine("{0} Time({1},{2})", manager.IndexToNode(index), solution.Min(endTimeVar),
+ solution.Max(endTimeVar));
+ Console.WriteLine("Time of the route: {0}min", solution.Min(endTimeVar));
+ totalTime += solution.Min(endTimeVar);
+ }
+ Console.WriteLine("Total time of all routes: {0}min", totalTime);
+ }
+
+ public static void Main(String[] args)
+ {
+ // Instantiate the data problem.
+ DataModel data = new DataModel();
+
+ // Create Routing Index Manager
+ RoutingIndexManager manager =
+ new RoutingIndexManager(data.TimeMatrix.GetLength(0), data.VehicleNumber, data.Depot);
+
+ // Create Routing Model.
+ RoutingModel routing = new RoutingModel(manager);
+
+ // Create and register a transit callback.
+ int transitCallbackIndex = routing.RegisterTransitCallback((long fromIndex, long toIndex) =>
+ {
+ // Convert from routing variable Index to distance matrix NodeIndex.
+ var fromNode = manager.IndexToNode(fromIndex);
+ var toNode = manager.IndexToNode(toIndex);
+ return data.TimeMatrix[fromNode, toNode];
+ });
+
+ // Define cost of each arc.
+ routing.SetArcCostEvaluatorOfAllVehicles(transitCallbackIndex);
+
+ // Add Distance constraint.
+ routing.AddDimension(transitCallbackIndex, // transit callback
+ 30, // allow waiting time
+ 30, // vehicle maximum capacities
+ false, // start cumul to zero
+ "Time");
+ RoutingDimension timeDimension = routing.GetMutableDimension("Time");
+
+ routing.AddConstantDimensionWithSlack(0, // transit var 0 for all
+ data.TimeMatrix.GetLength(0), // max value is every item being late
+ 1, // slack is 0 or 1 based on lateness
+ true, // start cumul to zero
+ "Late");
+
+ RoutingDimension lateDimension = routing.GetMutableDimension("Late");
+
+ // Add time window constraints for each location except depot.
+ for (int i = 1; i < data.TimeWindows.GetLength(0); ++i)
+ {
+ long index = manager.NodeToIndex(i);
+ var isLate = timeDimension.CumulVar(index) > data.TimeWindows[i, 1];
+
+ // set the slack var to 1 if late
+ routing.solver().MakeEquality(isLate, lateDimension.SlackVar(index));
+ }
+
+ // Instantiate route start and end times to produce feasible times.
+ for (int i = 0; i < data.VehicleNumber; ++i)
+ {
+ // add a fixed penalty for each late item
+ long penalty = 1000;
+ lateDimension.SetCumulVarSoftUpperBound(routing.End(0), 0, penalty);
+
+ routing.AddVariableMinimizedByFinalizer(lateDimension.CumulVar(routing.End(i)));
+ }
+
+ // Setting first solution heuristic.
+ RoutingSearchParameters searchParameters =
+ operations_research_constraint_solver.DefaultRoutingSearchParameters();
+ searchParameters.FirstSolutionStrategy = FirstSolutionStrategy.Types.Value.PathCheapestArc;
+
+ // Solve the problem.
+ Assignment solution = routing.SolveWithParameters(searchParameters);
+
+ // Print solution on console.
+ PrintSolution(data, routing, manager, solution);
+ }
+}
diff --git a/examples/contrib/vrptw_fixed_penalty.csproj b/examples/contrib/vrptw_fixed_penalty.csproj
new file mode 100644
index 0000000000..b439ead563
--- /dev/null
+++ b/examples/contrib/vrptw_fixed_penalty.csproj
@@ -0,0 +1,23 @@
+
+
+ Exe
+ 7.3
+ netcoreapp2.1
+ false
+
+ LatestMajor
+ Google.OrTools.vrptw_fixed_penalty
+ true
+
+
+
+ full
+ true
+ true
+
+
+
+
+
+
+
\ No newline at end of file