[Scip] Problems with SCIPcopy() and SCIPcopyProb()

[Stefan Vigerske]

Hi,

> I think I may have found a bug ... or I really don't understand something.
> ;-)
> The "ERROR: cannot call method<SCIPgetTransformedVar>  in problem creation
> stage" (see below)
> disappears when I change
>
> SCIP_VAR * ty = NULL;
> SCIP_CALL( SCIPgetTransformedVar(scip, y_vars(uv,s),&ty) );
                                    ^^^^

I guess that the scip here has to be sourcescip.
You should not pass in the new scip to get the transformed variable for 
a variable y_vars(uv,s) in the scip that you try to copy.


> to
>
> SCIP_VAR * ty = SCIPvarGetTransVar(y_vars(uv,s));
>
> Aren't those to calls supposed to be equivalent?

SCIPgetTransformedVar does some more checks and also works for negated 
variables.

Stefan

>
>    Daniel
>
> 2011/12/20 Daniel Karch<karch at math.tu-berlin.de>
>
>> Wow, that was fast! :-)
>>
>> Unfortunately, that does not work either:
>>
>> [src/scip/scip.c:187] ERROR: cannot call method<SCIPgetTransformedVar>  in
>> problem creation stage
>> [src/scip/scip.c:8817] ERROR: Error<-8>  in function call
>> [src/ProbDataMinCon.cpp:76] ERROR: Error<-8>  in function call
>> [src/objscip/objprobdata.cpp:162] ERROR: Error<-8>  in function call
>> [src/scip/prob.c:217] ERROR: Error<-8>  in function call
>> [src/scip/scip.c:1068] ERROR: Error<-8>  in function call
>> [src/scip/scip.c:1967] ERROR: Error<-8>  in function call
>> [src/scip/heur_rens.c:393] ERROR: Error<-8>  in function call
>> [src/scip/heur_rens.c:696] ERROR: Error<-8>  in function call
>> [src/scip/heur.c:398] ERROR: Error<-8>  in function call
>> [src/scip/solve.c:241] ERROR: Error<-8>  in function call
>> [src/scip/solve.c:3328] ERROR: Error<-8>  in function call
>> [src/scip/solve.c:3879] ERROR: Error<-8>  in function call
>> [src/scip/scip.c:7543] ERROR: Error<-8>  in function call
>> [src/scip/scipshell.c:135] ERROR: Error<-8>  in function call
>> [src/scip/scipshell.c:341] ERROR: Error<-8>  in function call
>> [src/cppmain.cpp:85] ERROR: Error<-8>  in function call
>> SCIP Error (-8): method cannot be called at this time in solution process
>>
>> Do I also have to implement the scip_trans callback?
>>
>>    Daniel
>>
>> P.S.: By the way, I think the documentation does not make it very clear
>> when the transformed variables have to be used ...
>>
>>
>>
>> 2011/12/20 Robert Schwarz<schwarz at zib.de>
>>
>>> Hi Daniel
>>>
>>> On 12/20/2011 11:17 AM, Daniel Karch wrote:
>>>> src/scip/scip.c:1422: SCIPcopyVars: Assertion
>>> `SCIPgetNIntVars(sourcescip)
>>>> + SCIPgetNBinVars(sourcescip)<= SCIPgetNIntVars(targetscip) +
>>>> SCIPgetNBinVars(targetscip)&&  SCIPgetNIntVars(targetscip) +
>>>> SCIPgetNBinVars(targetscip)<= SCIPgetNIntVars(sourcescip) +
>>>> SCIPgetNBinVars(sourcescip) + nfixedbinvars + nfixedintvars' failed.
>>>>
>>>> I get
>>>>
>>>> SCIPgetNIntVars(sourcescip) + SCIPgetNBinVars(sourcescip) +
>>> nfixedbinvars +
>>>> nfixedintvars == 25093
>>>>
>>>> and
>>>>
>>>> SCIPgetNIntVars(targetscip) + SCIPgetNBinVars(targetscip) == 27366
>>>>
>>>> After the presolving, the problem has 2273 binary variables, which is
>>>> exactly the difference here.
>>>> I figured out that the problem occurs in scip.c, l. 1966:
>>>>
>>>> /* create problem in the target SCIP and copying the source problem
>>> data */
>>>> SCIP_CALL( SCIPcopyProb(sourcescip, targetscip, localvarmap,
>>> localconsmap,
>>>> global, name) );
>>>>
>>>> /* copy all active variables */
>>>> SCIP_CALL( SCIPcopyVars(sourcescip, targetscip, localvarmap,
>>> localconsmap,
>>>> global) );
>>>>
>>>> The call to SCIPcopyProb() calls my scip_copy() callback and copies all
>>> the
>>>> variables, and the subsequent call to SCIPcopyVars() copies the active
>>>> variables *again*.
>>>> Now I don't really know what to do. The TSP example is the only one I am
>>>> aware of that implements the scip_copy() callback in the ProbData class,
>>>> and I did it just like it is
>>>> done there.
>>>>
>>>> Any suggestions?
>>>
>>> I just had the same problem. In your copy method of your ProbData class,
>>> you probably copy the variables of the original problem, whereas the
>>> SCIPcopyVars() line copies the variables of the transformed problem.
>>> This also explains the difference in cardinality.
>>>
>>> Otherwise SCIPgetVarCopy() can figure out which variables have already
>>> been copied.
>>>
>>> I suggest you also copy the transformed variables in your probdata,
>>> using SCIPgetTransformedVar.
>>>
>>> Hope that helps.
>>>
>>> --
>>> Robert Schwarz
>>> schwarz at zib.de
>>>
>>>
>>
>
>
>
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-- 
Stefan Vigerske
Humboldt University Berlin, Numerical Mathematics
http://www.math.hu-berlin.de/~stefan