Facility.java
/* Copyright 2021, 狗万app足彩Gurobi Optimization, LLC */ /*设施位置:一家公司目前将其产品狗万滚球球从5个工厂到4个仓库。它正在考虑关闭一些工厂以降低成本。为了减少运输和固定成本，公司应该关闭哪些工厂?狗万滚球球基于Frontline Systems的示例:http://www.solver.com/disfacilit手机万博登录y.htm经过许可使用。* /进口gurobi。*;public class Facility {public static void main(String[] args) {try{//仓库需求在千单位double demand [] = new double[] {15,18,14,20};容量[]= new double[] {20,22,17,19,18};//固定成本[]= new double[] {12000, 15000, 17000, 13000, 16000};//运输成本每千单位double transcost [][] = new double[][] {{4000, 2000, 3000, 2500, 4500}， {2500, 2600, 3400, 3000, 4000}， {1200, 1800, 2600, 4100, 3000}， {2200, 2600, 3100, 3700, 3200}};//工厂和仓库的数量int nPlants = Capacity.length; int nWarehouses = Demand.length; // Model GRBEnv env = new GRBEnv(); GRBModel model = new GRBModel(env); model.set(GRB.StringAttr.ModelName, "facility"); // Plant open decision variables: open[p] == 1 if plant p is open. GRBVar[] open = new GRBVar[nPlants]; for (int p = 0; p < nPlants; ++p) { open[p] = model.addVar(0, 1, FixedCosts[p], GRB.BINARY, "Open" + p); } // Transportation decision variables: how much to transport from // a plant p to a warehouse w GRBVar[][] transport = new GRBVar[nWarehouses][nPlants]; for (int w = 0; w < nWarehouses; ++w) { for (int p = 0; p < nPlants; ++p) { transport[w][p] = model.addVar(0, GRB.INFINITY, TransCosts[w][p], GRB.CONTINUOUS, "Trans" + p + "." + w); } } // The objective is to minimize the total fixed and variable costs model.set(GRB.IntAttr.ModelSense, GRB.MINIMIZE); // Production constraints // Note that the right-hand limit sets the production to zero if // the plant is closed for (int p = 0; p < nPlants; ++p) { GRBLinExpr ptot = new GRBLinExpr(); for (int w = 0; w < nWarehouses; ++w) { ptot.addTerm(1.0, transport[w][p]); } GRBLinExpr limit = new GRBLinExpr(); limit.addTerm(Capacity[p], open[p]); model.addConstr(ptot, GRB.LESS_EQUAL, limit, "Capacity" + p); } // Demand constraints for (int w = 0; w < nWarehouses; ++w) { GRBLinExpr dtot = new GRBLinExpr(); for (int p = 0; p < nPlants; ++p) { dtot.addTerm(1.0, transport[w][p]); } model.addConstr(dtot, GRB.EQUAL, Demand[w], "Demand" + w); } // Guess at the starting point: close the plant with the highest // fixed costs; open all others // First, open all plants for (int p = 0; p < nPlants; ++p) { open[p].set(GRB.DoubleAttr.Start, 1.0); } // Now close the plant with the highest fixed cost System.out.println("Initial guess:"); double maxFixed = -GRB.INFINITY; for (int p = 0; p < nPlants; ++p) { if (FixedCosts[p] > maxFixed) { maxFixed = FixedCosts[p]; } } for (int p = 0; p < nPlants; ++p) { if (FixedCosts[p] == maxFixed) { open[p].set(GRB.DoubleAttr.Start, 0.0); System.out.println("Closing plant " + p + "\n"); break; } } // Use barrier to solve root relaxation model.set(GRB.IntParam.Method, GRB.METHOD_BARRIER); // Solve model.optimize(); // Print solution System.out.println("\nTOTAL COSTS: " + model.get(GRB.DoubleAttr.ObjVal)); System.out.println("SOLUTION:"); for (int p = 0; p < nPlants; ++p) { if (open[p].get(GRB.DoubleAttr.X) > 0.99) { System.out.println("Plant " + p + " open:"); for (int w = 0; w < nWarehouses; ++w) { if (transport[w][p].get(GRB.DoubleAttr.X) > 0.0001) { System.out.println(" Transport " + transport[w][p].get(GRB.DoubleAttr.X) + " units to warehouse " + w); } } } else { System.out.println("Plant " + p + " closed!"); } } // Dispose of model and environment model.dispose(); env.dispose(); } catch (GRBException e) { System.out.println("Error code: " + e.getErrorCode() + ". " + e.getMessage()); } } }
