[Scip] Simple but wired problem with SCIP

[michael.winkler@zib.de]

Hi Mahdi,

I did not and cannot compile your file.

But I looked at your code and as you said, you want to B&B or B&C methods.
Then it might be useful and necessary to set your constraints to be not
modifiable, because you do not change your constraints during solving.
Also your BigM should be chosen more carefully, because such big
differences in coefficients may lead to numerical problems. (Probably BigM
= num_cust should be enough in your case.)
Another thing, before calling SCIPfree() you should release all variables
and constraints by calling SCIPreleaseVar() or SCIPreleaseCons()
respectively.

Useful doxygen documentation:

http://scip.zib.de/doc/html/cons__linear_8h.shtml#aa7aed137a4130b35b168812414413481
http://scip.zib.de/doc/html/scip_8h.shtml#a738c6f77f0dcbe17cf8faa97c7573585
http://scip.zib.de/doc/html/scip_8h.shtml#ae7055a40bc1c895c4acb118bcb8de4de

Best, Michael

> Hi
>
> I have a very strange problem and most probably very naive of me as well!
> I have a very simple pure binary model which I run in simple SCIP (no use
> of branch and price algorithm, only simple B&B algorithm).
> When SCIP solves it, it gives a wrong solution! as if there is no variable
> y and all x are one. but when I solve the generated LP file via CPLEX or
> SCIP bins they solve the problem correctly.
> I have attached the model and its LP file here.
> What can be wrong?
> Note that I want to solve the problem via B&B or B&C methods.
>
> Thanks,
> Mahdi
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