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### Diet.java

/* Copyright 2018, Gurobi Optimization, LLC */

/* Solve the classic diet model, showing how to add constraints
to an existing model. */

import gurobi.*;

public class Diet {

public static void main(String[] args) {
try {

// Nutrition guidelines, based on
// USDA Dietary Guidelines for Americans, 2005
// http://www.health.gov/DietaryGuidelines/dga2005/
String Categories[] =
new String[] { "calories", "protein", "fat", "sodium" };
int nCategories = Categories.length;
double minNutrition[] = new double[] { 1800, 91, 0, 0 };
double maxNutrition[] = new double[] { 2200, GRB.INFINITY, 65, 1779 };

// Set of foods
String Foods[] =
new String[] { "hamburger", "chicken", "hot dog", "fries",
"macaroni", "pizza", "salad", "milk", "ice cream" };
int nFoods = Foods.length;
double cost[] =
new double[] { 2.49, 2.89, 1.50, 1.89, 2.09, 1.99, 2.49, 0.89,
1.59 };

// Nutrition values for the foods
double nutritionValues[][] = new double[][] {
{ 410, 24, 26, 730 },   // hamburger
{ 420, 32, 10, 1190 },  // chicken
{ 560, 20, 32, 1800 },  // hot dog
{ 380, 4, 19, 270 },    // fries
{ 320, 12, 10, 930 },   // macaroni
{ 320, 15, 12, 820 },   // pizza
{ 320, 31, 12, 1230 },  // salad
{ 100, 8, 2.5, 125 },   // milk
{ 330, 8, 10, 180 }     // ice cream
};

// Model
GRBEnv env = new GRBEnv();
GRBModel model = new GRBModel(env);
model.set(GRB.StringAttr.ModelName, "diet");

// Create decision variables for the nutrition information,
// which we limit via bounds
GRBVar[] nutrition = new GRBVar[nCategories];
for (int i = 0; i < nCategories; ++i) {
nutrition[i] =
Categories[i]);
}

// Create decision variables for the foods to buy
for (int j = 0; j < nFoods; ++j) {
}

// The objective is to minimize the costs
model.set(GRB.IntAttr.ModelSense, GRB.MINIMIZE);

// Nutrition constraints
for (int i = 0; i < nCategories; ++i) {
GRBLinExpr ntot = new GRBLinExpr();
for (int j = 0; j < nFoods; ++j) {
}
}

// Solve
model.optimize();

System.out.println("\nAdding constraint: at most 6 servings of dairy");
GRBLinExpr lhs = new GRBLinExpr();

// Solve
model.optimize();

// Dispose of model and environment
model.dispose();
env.dispose();

} catch (GRBException e) {
System.out.println("Error code: " + e.getErrorCode() + ". " +
e.getMessage());
}
}

private static void printSolution(GRBModel model, GRBVar[] buy,
GRBVar[] nutrition) throws GRBException {
if (model.get(GRB.IntAttr.Status) == GRB.Status.OPTIMAL) {
System.out.println("\nCost: " + model.get(GRB.DoubleAttr.ObjVal));
for (int j = 0; j < buy.length; ++j) {
}
}
System.out.println("\nNutrition:");
for (int i = 0; i < nutrition.length; ++i) {
System.out.println(nutrition[i].get(GRB.StringAttr.VarName) + " " +
nutrition[i].get(GRB.DoubleAttr.X));
}
} else {
System.out.println("No solution");
}
}
}


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