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Defining a linear relaxation

Example of defining linear relaxations (this feature requires Xpress Optimizer in addition to Xpress Kalis)
  • knapsackalld_cp.mos: Integer knapsack problem with 'alldifferent' constraint solved with standard CP search.
  • knapsackalld_relax.mos: Defining a linear relaxation and corresponding search.
  • customrelax.mos: Defining a customized linear relaxation
Further explanation of this example: 'Xpress Kalis Reference Manual'[download all files]

Source Files


   CP example problems
   file knapsackalld_cp.mos
   Knapsack problem with additional alldifferent 
   constraint solved by standard CP search.

   (c) 2009 Artelys S.A. and Fair Isaac Corporation
       Creation: 2009, rev. Mar. 2013       
model "Knapsack with side constraints"
 uses "kalis"

  x1,x2,x3: cpvar                   ! Decision variables
  benefit : cpvar                   ! The objective to minimize

! Enable output printing
 setparam("kalis_verbose_level", 1)

! Setting name of variables for pretty printing
 setname(x1,"x1"); setname(x2,"x2"); setname(x3,"x3") 

! Set initial domains for variables
 setdomain(x1, {1,3,8,12})
 setdomain(x2, {1,3,8,12})
 setdomain(x3, {1,3,8,12})

! Knapsack constraint
 3*x1 + 5*x2 + 2*x3 >= 30

! Additional global constraint

! Objective function
 benefit = 5*x1 + 8*x2 + 4*x3

! Initial propagation
 res := cp_propagate

! Display bounds on objective after constraint propagation
 writeln("Constraints propagation objective ", benefit)

! Solve the problem
 if (cp_minimize(benefit)) then  
  cp_show_sol                      ! Output optimal solution to screen


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