public static void Run(string inputFile)
{
Console.WriteLine("Start Knapsack solver...");
//read input
string[] inputs = File.ReadAllLines(inputFile);
string[] line = inputs[0].Split(' ');
int N = Convert.ToInt32(line[0]); // number of objects to pick from
int K = Convert.ToInt32(line[1]); // capacity of the sack
//create solver
// GLOP_LINEAR_PROGRAMMING, CBC_MIXED_INTEGER_PROGRAMMING
Google.OrTools.LinearSolver.Solver solver
= Google.OrTools.LinearSolver.Solver.CreateSolver("knapsack", "CBC_MIXED_INTEGER_PROGRAMMING");
//objective
Objective objective = solver.Objective();
objective.SetMaximization();
//variables
Variable[] variables = solver.MakeBoolVarArray(N);
//constraints
Constraint capacityConstraint = solver.MakeConstraint(0, K);
for (int i = 0; i < N; i++)
{
//get input parameters
line = inputs[i + 1].Split(' ');
double value = Convert.ToDouble(line[0]);
double weight = Convert.ToDouble(line[1]);
Variable x = variables[i];
//add to objective
objective.SetCoefficient(x, value);
//add to constraint
capacityConstraint.SetCoefficient(x, weight);
}
MPSolverParameters solverParams = new MPSolverParameters();
Console.WriteLine("Start solving...");
int resultStatus = solver.Solve();
double resultObjective = 0.0;
string resultVariables = "";
Console.WriteLine("Solver finished");
Console.WriteLine("Solution status: " + resultStatus.ToString());
string outputFile = new FileInfo(inputFile).Directory.FullName + @"\output.txt";
if (File.Exists(outputFile))
{
File.Delete(outputFile);
}
if (resultStatus != Google.OrTools.LinearSolver.Solver.OPTIMAL)
{
resultStatus = 0;
Console.WriteLine("The problem don't have an optimal solution.");
}
else
{
resultStatus = 1;
Console.WriteLine("Solution objective: " + solver.Objective().Value().ToString());
resultObjective = solver.Objective().Value();
foreach (Variable x in variables)
{
if (resultVariables == "")
{
resultVariables = x.SolutionValue().ToString();
}
else
{
resultVariables += " " + x.SolutionValue().ToString();
}
}
Console.WriteLine("Solution variables: " + resultVariables.ToString());
}
using (System.IO.StreamWriter file = new System.IO.StreamWriter(outputFile))
{
file.WriteLine(resultObjective.ToString() + " " + resultStatus.ToString());
file.WriteLine(resultVariables);
}
}
static void TestSumArray()
{
Console.WriteLine("Running TestSumArray");
Solver solver = new Solver("TestSumArray", Solver.CLP_LINEAR_PROGRAMMING);
Variable[] x = solver.MakeBoolVarArray(10, "x");
Constraint ct1 = solver.Add(x.Sum() == 3);
CheckDoubleEq(ct1.GetCoefficient(x[0]), 1.0, "test1");
Constraint ct2 = solver.Add(-2 * x.Sum() == 3);
CheckDoubleEq(ct2.GetCoefficient(x[0]), -2.0, "test2");
LinearExpr[] array = new LinearExpr[] { x[0]+ 2.0, x[0] + 3, x[0] + 4 };
Constraint ct3 = solver.Add(array.Sum() == 1);
CheckDoubleEq(ct3.GetCoefficient(x[0]), 3.0, "test3");
CheckDoubleEq(ct3.Lb(), -8.0, "test4");
CheckDoubleEq(ct3.Ub(), -8.0, "test5");
}
