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params_vb.vb
' Copyright 2023, Gurobi Optimization, LLC */
' Use parameters that are associated with a model.
' A MIP is solved for a few seconds with different sets of parameters.
' The one with the smallest MIP gap is selected, and the optimization
' is resumed until the optimal solution is found.
Imports System
Imports Gurobi
Class params_vb
Shared Sub Main(args As String())
If args.Length < 1 Then
Console.Out.WriteLine("Usage: params_vb filename")
Return
End If
Try
' Read model and verify that it is a MIP
Dim env As New GRBEnv()
Dim m As New GRBModel(env, args(0))
If m.IsMIP = 0 Then
Console.WriteLine("The model is not an integer program")
Environment.Exit(1)
End If
' Set a 2 second time limit
m.Parameters.TimeLimit = 2.0
' Now solve the model with different values of MIPFocus
Dim bestModel As New GRBModel(m)
bestModel.Optimize()
For i As Integer = 1 To 3
m.Reset()
m.Parameters.MIPFocus = i
m.Optimize()
If bestModel.MIPGap > m.MIPGap Then
Dim swap As GRBModel = bestModel
bestModel = m
m = swap
End If
Next
' Finally, delete the extra model, reset the time limit and
' continue to solve the best model to optimality
m.Dispose()
bestModel.Parameters.TimeLimit = GRB.INFINITY
bestModel.Optimize()
Console.WriteLine("Solved with MIPFocus: " & bestModel.Parameters.MIPFocus)
Catch e As GRBException
Console.WriteLine("Error code: " + e.ErrorCode & ". " + e.Message)
End Try
End Sub
End Class
