Python version of network_routing ... Python Equivalents of "NewPermanentCallback" and BaseLNS

[Dirk Schroetter]

Folks,

trying to adapt the network_routing C++ example into a Python version. As I understand, the Python bindings do not use the 'BaseLNS' class but rather a specialized LNS inherits from a pure Python (object) [gleaned from steel_lns.py].

In order to build the DecisionBuilders in the network_routing example uses the contruct:

00925     DecisionBuilder* const inner_db =

00926         solver.MakePhase(decision_vars,

00927                          Solver::CHOOSE_RANDOM,

00928                          NewPermanentCallback(

00929                              this,

00930                              &NetworkRoutingSolver::EvaluateMarginalCost,

00931                              &usage_costs));

Could anyone point me to the correct formulation of the 'NewPermanentCallback'  part of this statement ?

Thanks a lot

/Dirk

[Laurent Perron]

It should be automatically done.

Please have a look at examples/python/tsp.py to see a python callback.

Thanks

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

/Dirk

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[Dirk Schroetter]

Hello Laurent,

thanks for the pointer. I looked at that example and I gleaned that you are referring to the SetCost() method in RoutingModel. Is there an equivalent mechanism for regular models based on pywrapcp ?

Thanks a lot,

/Dirk

[Laurent Perron]

You should just need to pass a method with the right signature to the solver.Phase() call.

It should work.

Thanks

Laurent Perron | Operations Research | lpe...@google.com | (33) 1 42 68 53 00

[Erica Kane]

It will work IF you call the right function, which is not Phase as you might expect, but

solver.VarEvalValStrPhase(nodes,
             selector_callback,
             solver.INT_VALUE_DEFAULT)

and I found that out after days of pain by digging into the SWIG files. For the details see

http://stackoverflow.com/questions/29090752/using-python-callbacks-via-swig-in-or-tools

Erica