Re: [Help-glpk] Objective value issue

[Mattia Buccarella]

I just read again the link you provided before and I noticed there is a posting that suggests a workaround to avoid the problem. I will do more trials to see if it works properly. If it will not work, I will provide an example of my model to investigate further.

For the moment, I really thank you for your help: I feel like your page will solve my issue.

Thanks again.

--

Mattia Buccarella

On Fri, Jul 11, 2014 at 5:45 PM, Heinrich Schuchardt <address@hidden> wrote:

Hello Mattia,

please, provide an example model.

Best regards

Heinrich Schuchardt

http://www.xypron.de

Am 11.07.14 um 17:41 schrieb Mattia Buccarella

> Thanks for your answer.
>
> The link you suggested is the one I already saw and discussed in my first
>
> email.
>
> My question is about the meaning of "constant", since all the terms in my
>
> objective function are functions of variables (i.e.: none of them is
>
> actually constant). Also, I would like to know if there is any way not to
>
> let this shift happen.
>
> Thank you again for your time.
>
>
>
> --
>
> Mattia Buccarella
>
>
>
>
>
> On Fri, Jul 11, 2014 at 5:35 PM, Heinrich Schuchardt <address@hidden>
>
> wrote:
>
>
>
> > Hello Mattia,
>
> >
>
> > please, read
>
> >
>
> > http://en.wikibooks.org/wiki/GLPK/Troubleshooting#Objective_shift_term_ignored_when_exported
>
> >
>
> > Best regards
>
> >
>
> > Heinrich Schuchardt
>
> >
>
> > http://www.xypron.de
>
> >
>
> > Am 11.07.14 um 17:20 schrieb Mattia Buccarella
>
> >
>
> > > Hello everyone,
>
> > >
>
> > >
>
> > >
>
> > > my name is Mattia and I am using glpsol in the development of my master
>
> > >
>
> > > thesis in computer science.
>
> > >
>
> > >
>
> > >
>
> > > I am writing to you all for something I could not find anywhere so far.
>
> > >
>
> > > When I use glpsol to solve my model (written in MathProg, with separate
>
> > >
>
> > > data input file), all the variables are configured properly as I expect
>
> > (I
>
> > >
>
> > > am referring to a "dummy" input I use to verify the correctness of my
>
> > >
>
> > > model). Nevertheless, the value of the objective function is shifted and
>
> > I
>
> > >
>
> > > get the following message:
>
> > >
>
> > >
>
> > >
>
> > > Model has been successfully generated
>
> > >
>
> > > *glp_mpl_build_prob: row obje; constant term 84384 ignored*
>
> > >
>
> > > GLPK Integer Optimizer, v4.52
>
> > >
>
> > > ...etc...
>
> > >
>
> > >
>
> > >
>
> > > Searching the web, I found somebody had a similar issue but it was not
>
> > >
>
> > > related to the objective function and also involved CPLEX (context very
>
> > >
>
> > > different from mine). Does anybody of you know what is happening? When I
>
> > >
>
> > > try to solve the model (same model, same input) with COIN-OR Cbc, through
>
> > >
>
> > > AMPL, it gives me the non-shifted value. Also, it does not tell me
>
> > anything
>
> > >
>
> > > about constant terms in the function. Also, I checked again and again my
>
> > >
>
> > > objective function: all the terms are functions of some variable, so
>
> > >
>
> > > nothing is really constant in the calculation.
>
> > >
>
> > >
>
> > >
>
> > > Thanks in advance for your help.
>
> > >
>
> > > Goodbye.
>
> > >
>
> > >
>
> > >
>
> > > --
>
> > >
>
> > > Mattia Buccarella
>
> > >
>
> > > _______________________________________________
>
> > >
>
> > > Help-glpk mailing list
>
> > >
>
> > > address@hidden
>
> > >
>
> > > https://lists.gnu.org/mailman/listinfo/help-glpk
>
> >