[Osi] CPLEX Error 1217: No solution exists

[Matthew Saltzman]

On Mon, 2008-06-02 at 18:00 -0400, Laszlo Ladanyi wrote:
> No bug.
> 
> Pure and implemented means that if a derived class does not implement it then 
> you get a compile time error. So it forces the user to think and implement 
> something for the method. However, there is a default implementation, so the 
> user can simply invoke the default implementation.

OK But the "user" in this case is OsiCpx, right?  So what's the right
behavior for OsiCpx?  Implement a method that just invokes the
base-class method?

> 
> --Laci
> 
> On Mon, 2 Jun 2008, Matthew Galati wrote:
> 
> > Umm... ok, header has pure (=0) but src has it implemented. Bug.
> >
> >> It looks to me like base implementation is pure virtual
> >>     /// Get objective function value
> >>     virtual double getObjValue() const = 0;
> >>
> >>
> >>
> >>> CPLEX wipes out all solution information as soon as you make any
> >>> change to the problem whatsoever. I don't believe that the objective
> >>> value is one of the things cached in the base class. If you look at
> >>> the current implementation of getObjVal() in OsiCpx, it tries to get
> >>> the objective value using CPXgetobjval(). If Cplex reports
> >>> CPXERR_NO_SOLN, then the function returns 0.0 by default. In the base
> >>> class, the default implementation of the getObjVal() function computes
> >>> the objective value on the fly from cached data, which I guess would
> >>> fix the problem. Try just commenting out the getObjVal() function in
> >>> OsiCpx or else call the base class implementation from there and see
> >>> if that does what you need.  If that works, we should probably make
> >>> that change.
> >>>
> >>> Cheers,
> >>>
> >>> Ted
> >>>
> >>>
> >>>
> >>> Matthew Galati wrote:
> >>>
> >>>> This might be related to an old discussion...
> >>>>
> >>>> Using OsiCpx, I do
> >>>>   initialSolve()
> >>>>   getObjValue()
> >>>>   addCols()
> >>>>   getObjValue()  --> returns CPLEX Error  1217: No solution exists
> >>>>
> >>>> This is just an LP. Earlier issues with caching seem to have to do
> >>>> with switching from MIP to LP, etc.
> >>>>
> >>>> It looks like some attempt to keep cache was already made. Any ideas?
> >>>> If needed, I can create a driver program to show this issue.
> >>>>
> >>>> int err = CPXaddcols(env_,
> >>>> getLpPtr(OsiCpxSolverInterface::KEEPCACHED_ROW),
> >>>>                       numcols, nz, const_cast<double*>(obj),
> >>>>                       start, index, elem,
> >>>>                       const_cast<double*>(collb),
> >>>>                       const_cast<double*>(colub), NULL );
> >>>>
> >>>> _______________________________________________
> >>>> Osi mailing list
> >>>> Osi at list.coin-or.org
> >>>> http://list.coin-or.org/mailman/listinfo/osi
> >>>>
> >>>
> >>
> >>
> >> _______________________________________________
> >> Osi mailing list
> >> Osi at list.coin-or.org
> >> http://list.coin-or.org/mailman/listinfo/osi
> >>
> >
> >
> > _______________________________________________
> > Osi mailing list
> > Osi at list.coin-or.org
> > http://list.coin-or.org/mailman/listinfo/osi
> >
> _______________________________________________
> Osi mailing list
> Osi at list.coin-or.org
> http://list.coin-or.org/mailman/listinfo/osi
-- 
                Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu
http://www.math.clemson.edu/~mjs