[Cbc] The Silence of the LPs

[John Forrest]

Dirk,

You will be better off using OsiClpSolverInterface rather than 
OsiCbcSolverInterface as OsiCbc is an unhappy mixture of linear solver 
and integer solver and is not much tested.

If you replace OsiCbc with OsiClp, derive the message handler from 
CbcMessageHandler and pass the message handler into the CbcModel then it 
should work as you expect.

John Forrest

On 22/01/14 17:37, Dirk Eßer wrote:
> Hi everybody!
>
> I just started porting an application of mine from lpsolver to CBC and 
> things work fine so far. There is one minor annoyance, though: despite 
> me defining my own "CoinMessageHandler" subclass and 
> "passInMessageHandler"-ing it into any "OsiSolverInterface" I can 
> find, there seems to be some code in the CBC library, which doesn't 
> care about my efforts, and insists on making itself heard.
>
> This is slightly annoying, since the application is a server 
> application, which solves a lot of (small to medium size) MIPs in a 
> row on client requests, and the messages from CBC tend to blow up the 
> log files considerably with noise, we are not interested in.
>
> The messages generated are "Cbc3007W" ("No integer variables - nothing 
> to do"), "Cbc0004I" ("Integer solution of x found after x iterations 
> and x nodes (x seconds)"), "Cbc0001I" ("Search completed - best 
> objective x, took x iterations and x nodes (x seconds)"), and 
> "Cbc0035I" ("Maximum depth x, x variables fixed on reduced cost").
>
> I'd rather not resolve this issue by brute force (say, via "FILE* p = 
> fopen("/dev/null", "w"); CoinMessageHandler printer(p); ..." -- if 
> that's at all viable).
>
> I am not using the "CbcSolver" class, only the "CbcModel" and 
> "Osi[Cbc]SolverInterface" and related APIs. The MIPs are generated 
> on-the-fly from data passed in by the client.
>
> Any input on this is greatly appreciated.
>
> Cheers,
> Dirk
>
> P.S. For reference, here's my message handler and set-up code.
>
>     class MessageHandler: public CoinMessageHandler
>     {
>     public:
>         MessageHandler(): CoinMessageHandler() {}
>         MessageHandler(const MessageHandler& r): CoinMessageHandler(r) {}
>         MessageHandler& operator= (const MessageHandler& r) { 
> CoinMessageHandler::operator=(r); return *this; }
>         virtual CoinMessageHandler* clone() { return new 
> MessageHandler(*this); }
>         virtual int print() { return 0; }
>     };
>
> which is injected before and after model construction:
>
>     void
>     matrix_builder::set_printer(OsiSolverInterface* pf, 
> MessageHandler& printer)
>     {
>         if (pf) pf->passInMessageHandler(&printer);
>     }
>
> and
>
>     OsiCbcSolverInterface iface;
>     CoinPackedMatrix pmx(false, num_columns, num_rows, num_elements, 
> matrix, columns, starts, lengths);
>
>     iface.setObjSense(-1.0);
>     iface.loadProblem(pmx, 0, 0, objective, senses, rights, 0);
>     iface.passInMessageHandler(&printer);
>
>     CbcModel model* = new CbcModel(iface);
>     ... a few more things to set up SOS and integer declarations ...
>
>     set_printer(model->solver(), printer);
>     set_printer(model->continuousSolver(), printer);
>     set_printer(model->referenceSolver(), printer);
>
> where "printer" is a reference to an instance of "MessageHandler".
>
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>