lp_vb.vb
' Copyright 2022, Gurobi Optimization, LLC ' ' This example reads an LP model from a file and solves it. ' If the model is infeasible or unbounded, the example turns off ' presolve and solves the model again. If the model is infeasible, ' the example computes an Irreducible Inconsistent Subsystem (IIS), ' and writes it to a file. Imports System Imports Gurobi Class lp_vb Shared Sub Main(ByVal args As String()) If args.Length < 1 Then Console.WriteLine("Usage: lp_vb filename") Return End If Try Dim env As GRBEnv = New GRBEnv("lp1.log") Dim model As GRBModel = New GRBModel(env, args(0)) model.Optimize() Dim optimstatus As Integer = model.Status If optimstatus = GRB.Status.INF_OR_UNBD Then model.Parameters.Presolve = 0 model.Optimize() optimstatus = model.Status End If If optimstatus = GRB.Status.OPTIMAL Then Dim objval As Double = model.ObjVal Console.WriteLine("Optimal objective: " & objval) ElseIf optimstatus = GRB.Status.INFEASIBLE Then Console.WriteLine("Model is infeasible") model.ComputeIIS() model.Write("model.ilp") ElseIf optimstatus = GRB.Status.UNBOUNDED Then Console.WriteLine("Model is unbounded") Else Console.WriteLine("Optimization was stopped with status = " & _ optimstatus) End If ' Dispose of model and env model.Dispose() env.Dispose() Catch e As GRBException Console.WriteLine("Error code: " & e.ErrorCode & ". " & e.Message) End Try End Sub End Class
