private ResultState SolveInternal()
{
PrintDebugRessourcesBefore("SolveInternal");
var param = new MPSolverParameters();
param.SetDoubleParam(MPSolverParameters.RELATIVE_MIP_GAP, MIP_GAP);
if (timelimit != 0)
{
solver.SetTimeLimit(timelimit);
}
#if DEBUG
solver.EnableOutput();
#else
solver.SuppressOutput();
#endif
resultState = FromGoogleResultState(solver.Solve(param));
PrintDebugRessourcesAfter();
#if DEBUG
PrintDebugOutput();
#endif
return(resultState);
}
static void Main(string[] args)
{
var @params = new MPSolverParameters();
@params.SetDoubleParam(MPSolverParameters.DoubleParam.RELATIVE_MIP_GAP, 0);
@params.SetDoubleParam(MPSolverParameters.DoubleParam.PRIMAL_TOLERANCE, 0);
@params.SetDoubleParam(MPSolverParameters.DoubleParam.DUAL_TOLERANCE, 0);
var solver = new Solver("BOP_Knapsack", (Solver.OptimizationProblemType) 12);
BuildModel(solver);
var result = solver.Solve(@params);
Console.WriteLine("Using BOP:");
Console.WriteLine("result: " + result);
Console.WriteLine("objective: " + solver.Objective().Value());
Console.WriteLine("bound: " + solver.Objective().BestBound());
solver = new Solver("CBC_Knapsack", (Solver.OptimizationProblemType) 5);
BuildModel(solver);
result = solver.Solve(@params);
Console.WriteLine("Using CBC:");
Console.WriteLine("result: " + result);
Console.WriteLine("objective: " + solver.Objective().Value());
Console.WriteLine("bound: " + solver.Objective().BestBound());
}
// TODO: TBD: taking LinearSolver assembly(ies) out of the build configuration for the time being until a usage/migration path can be established...
/// <summary>
/// Builds the <see cref="MPSolverParameters"/> instance given a set of
/// <see cref="MpParamSpec"/> pairs.
/// </summary>
/// <param name="specs"></param>
/// <returns></returns>
protected virtual MPSolverParameters BuildParameters(params MpParamSpec[] specs)
{
var parameters = new MPSolverParameters();
foreach (var(spec, value) in specs)
{
parameters.SetDoubleParam(spec.ForSolver(), value);
}
ClrCreatedObjects.Add(parameters);
return(parameters);
}
private MPSolverParameters BuildParameters(IEnumerable <double> values)
{
var parameters = new MPSolverParameters();
// ReSharper disable PossibleMultipleEnumeration
for (var i = 0; i < values.Count(); i++)
{
parameters.SetDoubleParam(i, values.ElementAt(i));
// ReSharper enable PossibleMultipleEnumeration
}
ClrCreatedObjects.Add(parameters);
return(parameters);
}
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);
}
}
