How to generate user cut or lazy cut

[zhic...@gmail.com]

Hi,

    I'm trying to use the user cut or lazy cut to solve my problem. But I find out the callback function will never be run during the solving. So I test an simple example, which is learned from sc_script example.

    I'm expecting to get at least one print out from three callback functions, but I don't. 

    Can anybody tell me what I did wrong?

=========test.py============

from pyomo.core import *

model = AbstractModel(name="Master")

model.x = Var(within=Integers, bounds=(0,2))

model.y = Var(within=Integers, bounds=(0,2))

def min_obj_rule(model):

return model.y

model.oMaster = Objective(rule=min_obj_rule,sense=minimize)

=========run.py=============

test_mdl = import_file("test.py").model

test_inst = test_mdl.create_instance()

def solve_callback(solver, test_inst ):

    print "CB-Solve"

def cut_callback(solver, test_inst ):

    print "CB-Cut"

def node_callback(solver, test_inst ):

    print "CB-Node"

opt = SolverFactory('_cplex_direct')

opt.set_callback('cut-callback', cut_callback)

opt.set_callback('node-callback', node_callback)

opt.set_callback('solve-callback', solve_callback)

results = opt.solve(test_inst , tee=True)

print results

==========results============

Warning: Control callbacks may disable some MIP features.

CPXPARAM_Read_DataCheck                          1

CPXPARAM_Read_APIEncoding                        "UTF-8"

CPXPARAM_MIP_Strategy_CallbackReducedLP          0

Found incumbent of value 0.000000 after 0.00 sec. (0.00 ticks)

Root node processing (before b&c):

  Real time             =    0.00 sec. (0.00 ticks)

Sequential b&c:

  Real time             =    0.00 sec. (0.00 ticks)

                          ------------

Total (root+branch&cut) =    0.00 sec. (0.00 ticks)

Problem: 

- Name: 

  Lower bound: None

  Upper bound: None

  Number of objectives: 1

  Number of constraints: 0

  Number of variables: 2

  Number of binary variables: 0

  Number of integer variables: 2

  Number of continuous variables: 0

  Number of nonzeros: None

  Sense: unknown

Solver: 

- Name: CPLEX 12.7.1.0

  Status: ok

  Return code: None

  Message: None

  User time: 0.0

  System time: None

  Wallclock time: None

  Termination condition: optimal

  Termination message: None

Solution: 

- number of solutions: 0

  number of solutions displayed: 0

[Watson, Jean-Paul]

A warning: the callback functionality in the direct interfaces that you currently see in Pyomo are at best prototypical, and really not even that - "experimental" might be the best word. We have newer and more comprehensive direct plugins in the pipeline, but they will not be ready for release for at least a few months.

That said, I'm not sure why your specific callbacks are not being invoked. I suspect it is because the instance is solved in pre-solve, given its relative difficulty.

Jpw

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