[Scip] Quick question on how to get infesibility info from presolver or after solve returns infeasible

[Guillermo Irisarri]

Hello Michael:

Thank you very much for your answer. I will try the MinUC suggestion.

In the meantime, I have a question about the usage if SCIP 3.0.0 in Windows (32) systems. I tried the new binary and could not make it work. 1) The linker found an unresolved reference for SCIPinfinity. I replaced that by DBL_MAX for the time being to get through that part, 2) When running the application Windows complains about not finding the "scip-3.0.0.win.x86.vc10.opt.spx.mt.exe", which is strange since this is the SCIP interactive application. I put that in the path, anyway, 3) The application started and failed with an exception in the first call to SCIP_CALL_EXC(SCIPcreate(&scip)). 

I did not see these problems with the scip-2.1.1 where the only thing I needed was the DLL scip-2.1.1.win.x86.vc10.opt.spx.dll (and the corresponding library). Is there something else needed besides the DLL/Lib?

I appreciate it very much if you let me know what may be happening here.

Thanks

Guillermo

-----Original Message-----
From: michael.winkler at zib.de [mailto:michael.winkler at zib.de] 
Sent: Sunday, October 07, 2012 7:20 PM
To: Guillermo Irisarri
Cc: Stefan Heinz; Scip at zib.de
Subject: Re: [Scip] Quick question on how to get infesibility info from presolver or after solve returns infeasible

Hi Guillermo,

for now there is no easy way determine a reason for infeasibility in SCIP.

Like Stefan suggested you can try the beta version changing a problem to a "MinUC" problem, determine the minimal number of unsatisfied constraints.
This can also be done via SCIPtransformMinUC().

Getting a (minimal) set of variables which led to infeasibility is not
(yet) possible (in any direct approach).

Best, Michael

> Thank you very much for your suggestion, Stefan. I am interested in 
> using SCIP integrated within a C++ application. As a consequence the 
> objective is to be able to get infeasibility information via some API 
> just as the other APIs used for problem setup and execution control. 
> It would be nice to get that sort of information for both the presolve 
> phase -- if that phase already identifies infeasibilities, -- and also 
> for the actual solution if there are any other infeasibilities at a 
> node not already picked up by the presolver.
>
> Are there any simple APIs for these purposes? Is it done via call backs?
> If any of these, are there any examples available?
>
> I thank you very much for your help
>
> Best regards
>
> Guillermo
>
> -----Original Message-----
> From: Stefan Heinz [mailto:heinz at zib.de]
> Sent: Tuesday, October 02, 2012 9:19 AM
> To: Guillermo Irisarri; Scip at zib.de
> Subject: Re: Quick question on how to get infesibility info from 
> presolver or after solve returns infeasible
>
> Hi,
>
> you can set the verbosity level to 5. This will give you some more 
> information.
>
> SCIP> set display verblevel 5
>
> Besides that you can try the beta version of the infeasibility 
> analysis
> tool:
>
> SCIP> read <file>
> SCIP> change minuc
> SCIP> optimize
>
> Best Stefan
>
>
> On 10/02/2012 03:10 PM, Guillermo Irisarri wrote:
>> Dear Mr Heinz:
>>
>> I have looked at the documentation and cannot find a way to get the 
>> information above out of SCIP. Could you point me in the right 
>> direction or, perhaps, give an idea on how to proceed. If there are 
>> any examples, a pointer to those would be very useful.
>
>>
>> Thanks
>>
>> Guillermo Irisarri
>>
>>
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