/// <summary>
/// Creates a new variable.
/// </summary>
/// <param name="solver">The model / solver instance this variable belongs to.</param>
/// <param name="variableType">The type of the variable.</param>
/// <param name="lb">The lower bound of the variable.</param>
/// <param name="ub">The upper bound of the variable.</param>
/// <param name="name">The name of the variable.</param>
public Variable(LinearModel solver, VariableType variableType, double lb, double ub, string name)
{
// Set active solver reference
Solver = solver;
Solver.RegisterVariable(this);
// Set parameters
_variableType = variableType;
// Instantiate the variable
switch (solver.Type)
{
case SolverType.CPLEX:
Expression =
(_variableType == VariableType.Continuous) ? solver.CplexModel.NumVar(lb, ub, NumVarType.Float) :
(_variableType == VariableType.Binary) ? solver.CplexModel.BoolVar(name) :
solver.CplexModel.IntVar((int)lb, (int)ub, name);
break;
case SolverType.Gurobi:
Expression =
solver.GurobiModel.AddVar(lb, ub, 0, (variableType == VariableType.Continuous) ? GRB.CONTINUOUS : (variableType == VariableType.Binary) ? GRB.BINARY : GRB.INTEGER, name);
break;
default: throw new ArgumentException("Unknown solver type: " + solver.Type);
}
}
public static LinearExpression Sum(IEnumerable <LinearExpression> expressions)
{
LinearModel solver = expressions.First().Solver;
switch (solver.Type)
{
case SolverType.CPLEX: { return(new LinearExpression()
{
Solver = solver, Expression = solver.CplexModel.Sum(expressions.Select(e => e.Expression as INumExpr).ToArray())
}); }
case SolverType.Gurobi:
{
GRBLinExpr expr = new GRBLinExpr();
foreach (var exp in expressions)
{
expr += exp.Expression;
}
return(new LinearExpression()
{
Solver = solver, Expression = expr
});
}
default: throw new ArgumentException("Unknown solver type: " + solver.Type);
}
}
//public class CplexStatusCallback : CpxIncumbentCallbackFunction, IStatusCallback
//{
// /// <summary>
// /// Creates a new callback.
// /// </summary>
// /// <param name="solver">The active solver.</param>
// public CplexStatusCallback(SolverWrapper solver) { _solver = solver; }
// /// <summary>
// /// The active solver.
// /// </summary>
// private SolverWrapper _solver;
// /// <summary>
// /// Logs messages of the solver.
// /// </summary>
// public Action<string> Logger { get; set; }
// /// <summary>
// /// Notifies about new incumbents.
// /// </summary>
// public Action NewIncumbent { get; set; }
// /// <summary>
// /// Logs new incumbent values.
// /// </summary>
// public Action<double> LogIncumbent { get; set; }
// public int CallIt(IntPtr xenv, IntPtr cbdata, int wherefrom, object cbhandle, double objval, double[] x, ref int isfeas_p, ref int useraction)
// {
// return 0;
// }
//}
#endregion
public static void Test(SolverType type)
{
Console.WriteLine("Is64BitProcess: " + Environment.Is64BitProcess);
LinearModel wrapper = new LinearModel(type, (string s) => { Console.Write(s); });
Console.WriteLine("Setting up model and optimizing it with " + wrapper.Type);
string x = "x"; string y = "y"; string z = "z";
List <string> variableNames = new List <string>()
{
x, y, z
};
VariableCollection <string> variables = new VariableCollection <string>(wrapper, VariableType.Binary, 0, 1, (string s) => { return(s); });
wrapper.SetObjective(0.5 * variables[x] + variables[y] + 4 * variables[z], OptimizationSense.Maximize);
wrapper.AddConstr(LinearExpression.Sum(variableNames.Select(v => 2 * variables[v])) <= 4, "Summation");
wrapper.AddConstr(variables[x] + variables[y] + variables[z] <= 2.0, "limit");
wrapper.AddConstr(variables[x] == variables[z], "equal");
wrapper.AddConstr(variables[x] * 2 == 2, "times");
wrapper.Update();
wrapper.Optimize();
Console.WriteLine("Solution:");
if (wrapper.HasSolution())
{
Console.WriteLine("Obj: " + wrapper.GetObjectiveValue());
foreach (var variableName in variableNames)
{
Console.WriteLine(variableName + ": " + variables[variableName].GetValue());
}
}
else
{
Console.WriteLine("No solution!");
}
}
/// <summary>
/// Creates a new collection of variables.
/// </summary>
/// <param name="solver">The solver the variable collection belongs to.</param>
/// <param name="variableType">The type of the variables in the collection.</param>
/// <param name="lowerBound">The default lower bound when adding a variable on-the-fly.</param>
/// <param name="upperBound">The default upper bound when adding a variable on-the-fly.</param>
public VarCollection(LinearModel solver, VariableType variableType, double lowerBound, double upperBound)
{
// Set parameters
_variableType = variableType;
LB = lowerBound;
UB = upperBound;
// Reference active solver
_solver = solver;
// Instantiate the collection
_variables = new Dictionary <object[], Variable>(new ObjectArrayEqualityComparer <object>());
}
public static LinearExpression Sum(IEnumerable <Variable> variables)
{
LinearModel solver = variables.First().Solver;
switch (solver.Type)
{
case SolverType.CPLEX: { return(new LinearExpression()
{
Solver = solver, Expression = solver.CplexModel.Sum(variables.Select(e => e.Expression as INumExpr).ToArray())
}); }
case SolverType.Gurobi:
{
GRBLinExpr expr = new GRBLinExpr();
expr.AddTerms(Enumerable.Repeat(1.0, variables.Count()).ToArray(), variables.Select(e => e.Expression as GRBVar).ToArray());
return(new LinearExpression()
{
Solver = solver, Expression = expr
});
}
default: throw new ArgumentException("Unknown solver type: " + solver.Type);
}
}
/// <summary>
/// Creates a new collection of variables.
/// </summary>
/// <param name="solver">The solver the variable collection belongs to.</param>
/// <param name="variableType">The type of the variables in the collection.</param>
/// <param name="lowerBound">The default lower bound when adding a variable on-the-fly.</param>
/// <param name="upperBound">The default upper bound when adding a variable on-the-fly.</param>
public VariableCollection(LinearModel solver, VariableType variableType, double lowerBound, double upperBound) : base(solver, variableType, lowerBound, upperBound)
{
}
/// <summary>
/// Creates a new callback.
/// </summary>
/// <param name="solver">The active solver.</param>
public CplexStatusCallback(LinearModel solver) : base()
{
_solver = solver;
}
/// <summary>
/// Creates a new callback.
/// </summary>
/// <param name="solver">The active solver.</param>
public GurobiStatusCallback(LinearModel solver)
{
_solver = solver;
}
