java - 将约束添加到数组列表中的问题

Question

我正在学习使用 Java API 编写优化问题代码，并且在将以下简单 LP 的最后约束保存到名为 Constraints 的数组列表中时遇到问题。如果没有这个，代码就会运行，但是，当我激活这行代码时，会弹出错误:Constraints.add(model.addEq(proportionalWeight[j], y));
而不是以下行:
model.addEq(proportionalWeight[j], y);

MWE:

import ilog.concert.*;
import ilog.cplex.*;
import java.util.*;

public class SimpleLP {

    public static void main(String[] args) {
        Solve();
    }
    public static void Solve() {
        int n = 4;
        int m = 3;

        double[] p = { 310.0, 380.0, 350.0, 285.0 };
        double[] v = { 480.0, 650.0, 580.0, 390.0 };
        double[] a = { 18.0, 15.0, 23.0, 12.0 }; 
        double[] c = { 10.0, 16.0, 8.0 }; 
        double[] V = { 6800.0, 8700.0, 5300.0 }; 

        try {

            IloCplex model = new IloCplex();

            IloNumVar[][] x = new IloNumVar[n][];
            for (int i = 0; i < n; i++) {
                x[i] = model.numVarArray(m, 0, Double.MAX_VALUE);
            }

            IloNumVar y = model.numVar(0, Double.MAX_VALUE);

            IloLinearNumExpr obj = model.linearNumExpr();
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    obj.addTerm(p[i], x[i][j]);
                }
            }

            model.addMaximize(obj);

            for (int i = 0; i < n; i++) {
                model.addLe(model.sum(x[i]), a[i]);
            }


            List<IloRange> Constraints = new ArrayList<IloRange>();

            IloLinearNumExpr [] usedWeightCap = new IloLinearNumExpr[m];
            IloLinearNumExpr [] usedVolumeCap = new IloLinearNumExpr[m];
            IloLinearNumExpr [] proportionalWeight = new IloLinearNumExpr[m];

            for (int j = 0; j < m; j++) {
                usedWeightCap[j] = model.linearNumExpr();
                usedVolumeCap[j] = model.linearNumExpr();
                proportionalWeight[j] = model.linearNumExpr();

                for (int i = 0; i < n; i++) {
                    usedWeightCap[j].addTerm(1.0, x[i][j]);
                    usedVolumeCap[j].addTerm(v[i], x[i][j]);
                    proportionalWeight[j].addTerm(1/c[j], x[i][j]);
                }
            }
            for (int j = 0; j < m; j++) {

                Constraints.add(model.addLe(usedWeightCap[j], c[j]));

                Constraints.add(model.addLe(usedVolumeCap[j], V[j]));

                //model.addEq(model.prod(1/c[j], usedWeightCap[j]), y);
                //Constraints.add(model.addEq(proportionalWeight[j], y)); /*This is my problem that I cannot add this constraint into the list*/
                model.addEq(proportionalWeight[j], y);
            }
            if (model.solve()) {
                System.out.println("Objective Value: "+ model.getObjValue());
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < m; j++) {
                        System.out.println("x*["+(i+1)+"]"+"["+(j+1)+"] : "+model.getValue(x[i][j]));
                    }
                }
                System.out.println("y* : "+ model.getValue(y));
            } else {
                System.out.println("Problem not solved :(");
            }

            model.end();

        } catch (IloException ex) {
            ex.printStackTrace();
        }
    }
}

<小时/>

如果有人能帮助我解决这个问题，我将不胜感激。
问候，
巴曼

Answer 1

我应该使用 model.diff(proportionalWeight[j], y), 0.0); 而不是 .addEq();