/// <summary>
/// The problem of integer programming:
/// Selection employees necessary to minimize the total cost
/// for given parameters of the cash amount and fixed productivity.
/// </summary>
/// <param name="selector">Contains cash amount and productivity</param>
/// <returns>Possible solutions for the composition of the team of employees</returns>
public override List <Dictionary <FellowWorker, int> > Select(StaffSelector selector)
{
SolverContext context = SolverContext.GetContext();
Model model = context.CreateModel();
// init fellow workers
Junior junior = selector.Staffs.Junior;
Middle middle = selector.Staffs.Middle;
Senior senior = selector.Staffs.Senior;
Lead lead = selector.Staffs.Lead;
// init decisions - counts of number of employees of different qualifications
Decision juniorDecision = new Decision(Domain.IntegerNonnegative, junior.GetQualificationString());
Decision middleDecision = new Decision(Domain.IntegerNonnegative, middle.GetQualificationString());
Decision seniorDecision = new Decision(Domain.IntegerNonnegative, senior.GetQualificationString());
Decision leadDecision = new Decision(Domain.IntegerNonnegative, lead.GetQualificationString());
model.AddDecisions(juniorDecision, middleDecision, seniorDecision, leadDecision);
// constraint of fixed productivity
model.AddConstraints("fixProductivity",
junior.Productivity * juniorDecision +
middle.Productivity * middleDecision +
senior.Productivity * seniorDecision +
lead.Productivity * leadDecision == selector.Productivity);
// constraint of max cash amount
model.AddConstraints("maxAmount",
junior.Salary * juniorDecision +
middle.Salary * middleDecision +
senior.Salary * seniorDecision +
lead.Salary * leadDecision <= selector.Amount);
// criterion of optimization - total cost
model.AddGoal("cost", GoalKind.Minimize,
junior.Salary * juniorDecision +
middle.Salary * middleDecision +
senior.Salary * seniorDecision +
lead.Salary * leadDecision);
Solution solution = context.Solve(new ConstraintProgrammingDirective());
// packing results
List <Dictionary <FellowWorker, int> > solutionsList = new List <Dictionary <FellowWorker, int> >();
while (solution.Quality != SolverQuality.Infeasible)
{
solutionsList.Add(PackSolutionInDictionary(new Decision[] {
juniorDecision,
middleDecision,
seniorDecision,
leadDecision
}, selector.Staffs));
solution.GetNext();
}
context.ClearModel();
return(solutionsList);
}
