ortools-clone/com/google/ortools/linearsolver/samples/LinearProgramming.java

// Copyright 2010-2011 Google
// 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.linearsolver.samples;

import com.google.ortools.linearsolver.MPConstraint;
import com.google.ortools.linearsolver.MPSolver;
import com.google.ortools.linearsolver.MPVariable;

/**
 * Linear programming example that shows how to use the API.
 *
 */

public class LinearProgramming {

  static {
    System.loadLibrary("jnilinearsolver");
  }


  private static void runLinearProgrammingExample(String solverType) {
    try {
      MPSolver solver = new MPSolver("LinearProgrammingExample",
                                     MPSolver.getSolverEnum(solverType));
      double infinity = solver.infinity();
      // x1, x2 and x3 are continuous non-negative variables.
      MPVariable x1 = solver.makeNumVar(0.0, infinity, "x1");
      MPVariable x2 = solver.makeNumVar(0.0, infinity, "x2");
      MPVariable x3 = solver.makeNumVar(0.0, infinity, "x3");

      // Maximize 10 * x1 + 6 * x2 + 4 * x3.
      solver.setObjectiveCoefficient(x1, 10);
      solver.setObjectiveCoefficient(x2, 6);
      solver.setObjectiveCoefficient(x3, 4);
      solver.setMaximization();

      // x1 + x2 + x3 <= 100.
      MPConstraint c0 = solver.makeConstraint(-infinity, 100.0);
      c0.setCoefficient(x1, 1);
      c0.setCoefficient(x2, 1);
      c0.setCoefficient(x3, 1);

      // 10 * x1 + 4 * x2 + 5 * x3 <= 600.
      MPConstraint c1 = solver.makeConstraint(-infinity, 600.0);
      c1.setCoefficient(x1, 10);
      c1.setCoefficient(x2, 4);
      c1.setCoefficient(x3, 5);

      // 2 * x1 + 2 * x2 + 6 * x3 <= 300.
      MPConstraint c2 = solver.makeConstraint(-infinity, 300.0);
      c2.setCoefficient(x1, 2);
      c2.setCoefficient(x2, 2);
      c2.setCoefficient(x3, 6);

      System.out.println("Number of variables = " + solver.numVariables());
      System.out.println("Number of constraints = " + solver.numConstraints());

      int resultStatus = solver.solve();

      // Check that the problem has an optimal solution.
      if (resultStatus != MPSolver.OPTIMAL) {
        System.err.println("The problem does not have an optimal solution!");
        return;
      }

      System.out.println("Problem solved in " + solver.wallTime() +
                         " milliseconds");

      // The objective value of the solution.
      System.out.println("Optimal objective value = " +
                         solver.objectiveValue());

      // The value of each variable in the solution.
      System.out.println("x1 = " + x1.solutionValue());
      System.out.println("x2 = " + x2.solutionValue());
      System.out.println("x3 = " + x3.solutionValue());

      System.out.println("Advanced usage:");
      System.out.println("Problem solved in " + solver.iterations() +
                         " iterations");
      System.out.println("x1: reduced cost = " + x1.reducedCost());
      System.out.println("x2: reduced cost = " + x2.reducedCost());
      System.out.println("x3: reduced cost = " + x3.reducedCost());
      System.out.println("c0: dual value = " + c0.dualValue());
      System.out.println("    activity = " + c0.activity());
      System.out.println("c1: dual value = " + c1.dualValue());
      System.out.println("    activity = " + c1.activity());
      System.out.println("c2: dual value = " + c2.dualValue());
      System.out.println("    activity = " + c2.activity());
    } catch (java.lang.Exception exc) {
      System.out.println("- Solver not supported.");
    }
  }

  public static void main(String[] args) throws Exception {
    System.out.println("---- Linear programming example with GLPK ----");
    runLinearProgrammingExample("GLPK_LINEAR_PROGRAMMING");
    System.out.println("---- Linear programming example with CLP ----");
    runLinearProgrammingExample("CLP_LINEAR_PROGRAMMING");
  }
}