Class: MIPPeR::GLPKModel

Inherits:
Model
  • Object
show all
Defined in:
lib/mipper/glpk/model.rb

Instance Attribute Summary collapse

Attributes inherited from Model

#constraints, #variables

Instance Method Summary collapse

Methods inherited from Model

#<<, #compute_iis, #objective_value, #status, #update, #variable_value

Constructor Details

#initialize ⇒ GLPKModel

Returns a new instance of GLPKModel.



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# File 'lib/mipper/glpk/model.rb', line 5

def initialize
  fail unless MIPPeR.const_defined?(:GLPK)

  super

  @var_count = 0
  @constr_count = 0

  # Constraint matrix initialization (see #add_constraints)
  @ia = [0]
  @ja = [0]
  @ar = [0]

  # Disable terminal output
  GLPK.glp_term_out GLPK::GLP_OFF

  # Construct a new model
  @ptr = FFI::AutoPointer.new GLPK.glp_create_prob,
                              GLPK.method(:glp_delete_prob)
end

Instance Attribute Details

#ptr ⇒ Object (readonly)

Returns the value of attribute ptr.



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# File 'lib/mipper/glpk/model.rb', line 3

def ptr
  @ptr
end

Instance Method Details

#optimize ⇒ Object

Optimize the model



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# File 'lib/mipper/glpk/model.rb', line 46

def optimize
  # Ensure pending variables and constraints are added
  update

  # Run the solver and save the status for later
  iocp = GLPK::IOCP.new
  GLPK.glp_init_iocp iocp
  iocp[:presolve] = GLPK::GLP_ON
  status = GLPK.glp_intopt(@ptr, iocp)

  save_solution status
end

#sense=(sense) ⇒ Object

Set the sense of the model



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# File 'lib/mipper/glpk/model.rb', line 39

def sense=(sense)
  @sense = sense
  sense = sense == :min ? GLPK::GLP_MIN : GLPK::GLP_MAX
  GLPK.glp_set_obj_dir @ptr, sense
end

#set_variable_bounds(var_index, lb, ub) ⇒ Object 



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# File 'lib/mipper/glpk/model.rb', line 59

def set_variable_bounds(var_index, lb, ub)
  # Determine the type of the variable bounds
  if lb == ub
    type = GLPK::GLP_FX
  elsif lb.finite?
    type = ub.finite? ? GLPK::GLP_DB : GLPK::GLP_LO
  else
    type = ub.finite? ? GLPK::GLP_UP : GLPK::GLP_FR
  end

  # Set the bounds on the variable
  GLPK.glp_set_col_bnds(@ptr, var_index, type, lb, ub)
end

#write_lp(filename) ⇒ Object

Write the model to a file in CPLEX LP format



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# File 'lib/mipper/glpk/model.rb', line 27

def write_lp(filename)
  ret = GLPK.glp_write_lp @ptr, 0, filename
  fail if ret != 0
end

#write_mps(filename) ⇒ Object

Write the model to a file in MPS format



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# File 'lib/mipper/glpk/model.rb', line 33

def write_mps(filename)
  ret = GLPK.glp_write_mps @ptr, GLPK::GLP_MPS_FILE, nil, filename
  fail if ret != 0
end