Attribute VB_Name = "mip"
Option Explicit

'    Maximize z =  17 * x1 + 12* x2
'    subject to
'      10 x1 + 7 x2 <= 40
'         x1 +   x2 <=  5
'    where,
'      0.0 <= x1  integer
'      0.0 <= x2  integer
Sub mip()
  Dim lp As Long
  Dim iocp As glp_iocp
  Dim ind(2) As Long
  Dim val(2) As Double
  Dim ret As Integer
  Dim name(36) As Byte

  ' Create problem
  lp = glp_create_prob()
  str2bytes "Mixed Integer Problem", name
  glp_set_prob_name lp, name(0)

  ' Define columns
  glp_add_cols lp, 2
  str2bytes "x1", name
  glp_set_col_name lp, 1, name(0)
  glp_set_col_kind lp, 1, GLP_IV
  glp_set_col_bnds lp, 1, GLP_LO, 0#, 0#
  str2bytes "x2", name
  glp_set_col_name lp, 2, name(0)
  glp_set_col_kind lp, 2, GLP_IV
  glp_set_col_bnds lp, 2, GLP_LO, 0#, 0#

  ' Create constraints
  glp_add_rows lp, 2
  
  str2bytes "c1", name
  glp_set_row_name lp, 1, name(0)
  glp_set_row_bnds lp, 1, GLP_UP, 0, 40#
  ind(1) = 1
  ind(2) = 2
  val(1) = 10#
  val(2) = 7#
  glp_set_mat_row lp, 1, 2, ind(0), val(0)

  str2bytes "c2", name
  glp_set_row_name lp, 2, name(0)
  glp_set_row_bnds lp, 2, GLP_UP, 0, 5#
  ind(1) = 1
  ind(2) = 2
  val(1) = 1#
  val(2) = 1#
  glp_set_mat_row lp, 2, 2, ind(0), val(0)

  ' Define objective
  str2bytes "obj", name
  glp_set_obj_name lp, name(0)
  glp_set_obj_dir lp, GLP_MAX
  glp_set_obj_coef lp, 0, 0#
  glp_set_obj_coef lp, 1, 17#
  glp_set_obj_coef lp, 2, 12#

  ' Write model to file
  str2bytes "c:\temp\mip.lp", name
  ret = glp_write_lp(lp, 0, name(0))

  ' Solve model
  glp_init_iocp iocp
  iocp.presolve = GLP_ON
  ret = glp_intopt(lp, iocp)
    
  ' Retrieve solution
  If ret = 0 Then
    write_mip_solution (lp)
  Else
    Debug.Print "The problem could not be solved"
  End If
    
  ' Free memory
    glp_delete_prob lp
End Sub