116 lines
3.6 KiB
C#
116 lines
3.6 KiB
C#
// Copyright 2010-2018 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// [START program]
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// [START import]
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using System;
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using Google.OrTools.LinearSolver;
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// [END import]
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// [START program_part1]
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public class BinPackingMip {
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// [START data_model]
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class DataModel {
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public static double[] Weights = {48, 30, 19, 36, 36, 27,
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42, 42, 36, 24, 30};
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public int NumItems = Weights.Length;
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public int NumBins = Weights.Length;
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public double BinCapacity = 100.0;
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}
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// [END data_model]
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public static void Main() {
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// [START data]
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DataModel data = new DataModel();
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// [END data]
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// [END program_part1]
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// [START solver]
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// Create the linear solver with the SCIP backend.
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Solver solver = Solver.CreateSolver("SCIP");
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// [END solver]
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// [START program_part2]
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// [START variables]
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Variable[, ] x = new Variable[data.NumItems, data.NumBins];
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for (int i = 0; i < data.NumItems; i++) {
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for (int j = 0; j < data.NumBins; j++) {
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x[i, j] = solver.MakeIntVar(0, 1, $"x_{i}_{j}");
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}
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}
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Variable[] y = new Variable[data.NumBins];
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for (int j = 0; j < data.NumBins; j++) {
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y[j] = solver.MakeIntVar(0, 1, $"y_{j}");
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}
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// [END variables]
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// [START constraints]
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for (int i = 0; i < data.NumItems; ++i) {
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Constraint constraint = solver.MakeConstraint(1, 1, "");
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for (int j = 0; j < data.NumBins; ++j) {
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constraint.SetCoefficient(x[i, j], 1);
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}
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}
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for (int j = 0; j < data.NumBins; ++j) {
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Constraint constraint =
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solver.MakeConstraint(0, Double.PositiveInfinity, "");
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constraint.SetCoefficient(y[j], data.BinCapacity);
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for (int i = 0; i < data.NumItems; ++i) {
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constraint.SetCoefficient(x[i, j], -DataModel.Weights[i]);
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}
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}
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// [END constraints]
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// [START objective]
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Objective objective = solver.Objective();
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for (int j = 0; j < data.NumBins; ++j) {
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objective.SetCoefficient(y[j], 1);
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}
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objective.SetMinimization();
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// [END objective]
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// [START solve]
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Solver.ResultStatus resultStatus = solver.Solve();
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// [END solve]
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// [START print_solution]
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// Check that the problem has an optimal solution.
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if (resultStatus != Solver.ResultStatus.OPTIMAL) {
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Console.WriteLine("The problem does not have an optimal solution!");
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return;
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}
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Console.WriteLine($"Number of bins used: {solver.Objective().Value()}");
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double TotalWeight = 0.0;
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for (int j = 0; j < data.NumBins; ++j) {
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double BinWeight = 0.0;
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if (y [j]
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.SolutionValue() == 1) {
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Console.WriteLine($"Bin {j}");
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for (int i = 0; i < data.NumItems; ++i) {
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if (x [i, j]
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.SolutionValue() == 1) {
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Console.WriteLine($"Item {i} weight: {DataModel.Weights[i]}");
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BinWeight += DataModel.Weights[i];
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}
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}
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Console.WriteLine($"Packed bin weight: {BinWeight}");
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TotalWeight += BinWeight;
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}
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}
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Console.WriteLine($"Total packed weight: {TotalWeight}");
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// [END print_solution]
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}
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}
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// [END program_part2]
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// [END program]
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