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qp_vb.vb
' Copyright 2020, Gurobi Optimization, LLC
' This example formulates and solves the following simple QP model:
'
' minimize x^2 + x*y + y^2 + y*z + z^2 + 2 x
' subject to x + 2 y + 3 z >= 4
' x + y >= 1
' x, y, z non-negative
'
' It solves it once as a continuous model, and once as an integer model.
'
Imports Gurobi
Class qp_vb
Shared Sub Main()
Try
Dim env As New GRBEnv("qp.log")
Dim model As New GRBModel(env)
' Create variables
Dim x As GRBVar = model.AddVar(0.0, 1.0, 0.0, GRB.CONTINUOUS, "x")
Dim y As GRBVar = model.AddVar(0.0, 1.0, 0.0, GRB.CONTINUOUS, "y")
Dim z As GRBVar = model.AddVar(0.0, 1.0, 0.0, GRB.CONTINUOUS, "z")
' Set objective
Dim obj As New GRBQuadExpr()
obj = x*x + x*y + y*y + y*z + z*z + 2*x
model.SetObjective(obj)
' Add constraint: x + 2 y + 3 z >= 4
model.AddConstr(x + 2 * y + 3 * z >= 4.0, "c0")
' Add constraint: x + y >= 1
model.AddConstr(x + y >= 1.0, "c1")
' Optimize model
model.Optimize()
Console.WriteLine(x.VarName & " " & x.X)
Console.WriteLine(y.VarName & " " & y.X)
Console.WriteLine(z.VarName & " " & z.X)
Console.WriteLine("Obj: " & model.ObjVal & " " & obj.Value)
' Change variable types to integer
x.VType = GRB.INTEGER
y.VType = GRB.INTEGER
z.VType = GRB.INTEGER
' Optimize model
model.Optimize()
Console.WriteLine(x.VarName & " " & x.X)
Console.WriteLine(y.VarName & " " & y.X)
Console.WriteLine(z.VarName & " " & z.X)
Console.WriteLine("Obj: " & model.ObjVal & " " & obj.Value)
' 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
