Microsoft Solver Foundation：將循環中的決策變量添加到約束條件

Question

我試圖在Visual Studio 2010中使用Microsoft Solver Foundation與VB.NET創建優化模型。基本上，我有一個3種類型的員工列表，需要僱用（調酒師，服務員和女主人），每個人都有不同的工資和績效評級。我爲每個潛在員工創建了一個決策變量。它被設置爲0作爲無僱傭決定，1作爲僱用決定。

當我嘗試計算員工總成本，總績效分數或每種員工類型的總和時，我收到一個錯誤，指出我的決策變量尚未具有價值。

是否有一種更簡單的方法來添加這些約束（可能在一個循環中），而無需在每個約束中單獨列出整個僱員數據庫的每個決策變量？

這是我正在使用的代碼。

Dim myEmployee As Employee 
    Dim context As SolverContext = SolverContext.GetContext() 
    Dim model As Model = context.CreateModel() 
    For Each myEmployee In employeeList 
     If myEmployee.Type = "Bartender" Then 
      Dim BartenderHire As New Decision(Domain.IntegerRange(0, 1), myEmployee.ID) 
      barDecisionList.Add(BartenderHire) 
     ElseIf myEmployee.Type = "Host(ess)" Then 
      Dim HostHire As New Decision(Domain.IntegerRange(0, 1), myEmployee.ID) 
      hostDecisionList.Add(HostHire) 
     ElseIf myEmployee.Type = "Waiter/Waitress" Then 
      Dim WaiterHire As New Decision(Domain.IntegerRange(0, 1), myEmployee.ID) 
      waitDecisionList.Add(WaiterHire) 
     End If 
    Next 

    For i = 0 To barDecisionList.Count - 1 
     model.AddDecision(barDecisionList.Item(i)) 
    Next 
    For i = 0 To hostDecisionList.Count - 1 
     model.AddDecision(hostDecisionList.Item(i)) 
    Next 
    For i = 0 To waitDecisionList.Count - 1 
     model.AddDecision(waitDecisionList.Item(i)) 
    Next 

    'Calculate cost of hired employees. 
    Dim cost As Double 
    cost = 0 
    For i = 0 To model.Decisions.Count - 1 
     Dim thisEmployee As Employee = employeeList.Item(i) 
     cost = cost + (model.Decisions(i).ToDouble * thisEmployee.Wage * 6) 
    Next 

    'Calculate total score of hired employees. 
    Dim totalScore As Double 
    totalScore = 0 
    For i = 0 To model.Decisions.Count - 1 
     Dim thisEmployee As Employee = employeeList.Item(i) 
     totalScore = totalScore + (model.Decisions(i).ToDouble * thisEmployee.Score) 
    Next 

    'Calculate total bartenders hired. 
    Dim barSum As Integer 
    barSum = 0 
    For i = 0 To barDecisionList.Count - 1 
     barSum = barSum + barDecisionList.Item(i) 
    Next 

    'Calculate total waiters hired. 
    Dim waitSum As Integer 
    waitSum = 0 
    For i = 0 To waitDecisionList.Count - 1 
     waitSum = waitSum + waitDecisionList.Item(i) 
    Next 

    'Calculate total hosts hired. 
    Dim hostSum As Integer 
    hostSum = 0 
    For i = 0 To hostDecisionList.Count - 1 
     hostSum = hostSum + hostDecisionList.Item(i) 
    Next 

    'Add constraints 
    model.AddConstraint("Bartenders_Required", barSum = bartendersRequired) 
    model.AddConstraint("WaitStaff_Required", waitSum = waitersRequired) 
    model.AddConstraint("Hosts_Required", hostSum = hostsRequired) 
    model.AddConstraint("Budget", cost <= budget) 
    model.AddGoal("Total_Score", GoalKind.Maximize, totalScore) 
    Dim solution As Solution = context.Solve(New SimplexDirective()) 
    Dim report As Report = solution.GetReport 
    For i = 0 To model.Decisions.Count - 1 
     solutionList.Add(model.Decisions(i)) 
    Next 

Answer 1

的決定不會有值，直到你打電話context.Solve(...)後。