c34026b101
note: done using ```sh git grep -l "2010-2024 Google" | xargs sed -i 's/2010-2024 Google/2010-2025 Google/' ```
110 lines
3.7 KiB
Java
110 lines
3.7 KiB
Java
// Copyright 2010-2025 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.
|
|
|
|
package com.google.ortools.sat.samples;
|
|
|
|
import com.google.ortools.Loader;
|
|
import com.google.ortools.sat.CpModel;
|
|
import com.google.ortools.sat.CpSolver;
|
|
import com.google.ortools.sat.CpSolverStatus;
|
|
import com.google.ortools.sat.IntVar;
|
|
import com.google.ortools.sat.LinearExpr;
|
|
import com.google.ortools.sat.LinearExprBuilder;
|
|
import com.google.ortools.sat.Literal;
|
|
|
|
/** Solves a bin packing problem with the CP-SAT solver. */
|
|
public class BinPackingProblemSat {
|
|
public static void main(String[] args) throws Exception {
|
|
Loader.loadNativeLibraries();
|
|
// Data.
|
|
int binCapacity = 100;
|
|
int slackCapacity = 20;
|
|
int numBins = 5;
|
|
|
|
int[][] items = new int[][] {{20, 6}, {15, 6}, {30, 4}, {45, 3}};
|
|
int numItems = items.length;
|
|
|
|
// Model.
|
|
CpModel model = new CpModel();
|
|
|
|
// Main variables.
|
|
IntVar[][] x = new IntVar[numItems][numBins];
|
|
for (int i = 0; i < numItems; ++i) {
|
|
int numCopies = items[i][1];
|
|
for (int b = 0; b < numBins; ++b) {
|
|
x[i][b] = model.newIntVar(0, numCopies, "x_" + i + "_" + b);
|
|
}
|
|
}
|
|
|
|
// Load variables.
|
|
IntVar[] load = new IntVar[numBins];
|
|
for (int b = 0; b < numBins; ++b) {
|
|
load[b] = model.newIntVar(0, binCapacity, "load_" + b);
|
|
}
|
|
|
|
// Slack variables.
|
|
Literal[] slacks = new Literal[numBins];
|
|
for (int b = 0; b < numBins; ++b) {
|
|
slacks[b] = model.newBoolVar("slack_" + b);
|
|
}
|
|
|
|
// Links load and x.
|
|
for (int b = 0; b < numBins; ++b) {
|
|
LinearExprBuilder expr = LinearExpr.newBuilder();
|
|
for (int i = 0; i < numItems; ++i) {
|
|
expr.addTerm(x[i][b], items[i][0]);
|
|
}
|
|
model.addEquality(expr, load[b]);
|
|
}
|
|
|
|
// Place all items.
|
|
for (int i = 0; i < numItems; ++i) {
|
|
LinearExprBuilder expr = LinearExpr.newBuilder();
|
|
for (int b = 0; b < numBins; ++b) {
|
|
expr.add(x[i][b]);
|
|
}
|
|
model.addEquality(expr, items[i][1]);
|
|
}
|
|
|
|
// Links load and slack.
|
|
int safeCapacity = binCapacity - slackCapacity;
|
|
for (int b = 0; b < numBins; ++b) {
|
|
// slack[b] => load[b] <= safeCapacity.
|
|
model.addLessOrEqual(load[b], safeCapacity).onlyEnforceIf(slacks[b]);
|
|
// not(slack[b]) => load[b] > safeCapacity.
|
|
model.addGreaterOrEqual(load[b], safeCapacity + 1).onlyEnforceIf(slacks[b].not());
|
|
}
|
|
|
|
// Maximize sum of slacks.
|
|
model.maximize(LinearExpr.sum(slacks));
|
|
|
|
// Solves and prints out the solution.
|
|
CpSolver solver = new CpSolver();
|
|
CpSolverStatus status = solver.solve(model);
|
|
System.out.println("Solve status: " + status);
|
|
if (status == CpSolverStatus.OPTIMAL) {
|
|
System.out.printf("Optimal objective value: %f%n", solver.objectiveValue());
|
|
for (int b = 0; b < numBins; ++b) {
|
|
System.out.printf("load_%d = %d%n", b, solver.value(load[b]));
|
|
for (int i = 0; i < numItems; ++i) {
|
|
System.out.printf(" item_%d_%d = %d%n", i, b, solver.value(x[i][b]));
|
|
}
|
|
}
|
|
}
|
|
System.out.println("Statistics");
|
|
System.out.println(" - conflicts : " + solver.numConflicts());
|
|
System.out.println(" - branches : " + solver.numBranches());
|
|
System.out.println(" - wall time : " + solver.wallTime() + " s");
|
|
}
|
|
}
|