[SCIP] Infeasible with C-API but feasible with Interactive Shell

[Ambros Gleixner]

Hi Rich,

One natural thing to try would be: write the feasible solution found by 
the shell into a sol file and read this in your API code.  If the 
solution is rejected, looking at the violated constraint will bring us 
closer to the source of the problem.

Expert mode: compile with cmake -DDEBUGSOL=on and pass the path to the 
solfile to parameter "misc/debugsol".  Then SCIP will check and print 
where it is cut off.

Best,
Ambros



Am 11.07.2018 um 05:48 schrieb Levinson, Richard J. (ARC-TI)[SGT, INC]:
> I have now upgraded to SCIP 6.0.0 and still have the same problem.
> 
> The solver returns 'infeasible' with the C-API but is feasible with the 
> interactive shell.
> 
> I am literally copying model text from the scip log of the infeasible 
> run into a .cip file and then reading it into the interactive shell, 
> where a feasible solution is found and no changes to the model at all.  
> Now both cases are using SCIP 6.0.0 so it is not a version issue.
> 
> - Rich
> ------------------------------------------------------------------------
> *From:* Levinson, Richard J. (ARC-TI)[SGT, INC]
> *Sent:* Tuesday, July 10, 2018 3:58 PM
> *To:* Scip at zib.de
> *Subject:* Infeasible with C-API but feasible with Interactive Shell
> 
> Hello,
> 
> I have a SCIP model generated using the C-API. It returns 'infeasible' 
> when I call solve() programmatically, but if I copy the SCIP "original 
> problem" output from the SCIP log file of the 'infeasible' run, and copy 
> it directly into a .cip file and read it back in through the interactive 
> shell, then it is 'feasible'.
> 
> The C-API is being linked against SCIP 4.0 but the model is feasible in 
> the SCIP 4.0 interactive shell (as well as the SCIP 6.0 interactive shell).
> 
> Any suggestions about how to diagnose and resolve this discrepancy? I 
> need to be able to generate the model and solve via C-API. Is there a 
> good way to figure out why it's being marked infeasible via the C-API?
> 
> Thank you,
> 
>     Rich Levinson
> 
> 
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-- 
Ambros Gleixner, Research Group Mathematical Optimization Methods at 
Zuse Institute Berlin, http://www.zib.de/gleixner