[Cgl] cgl, cpx, mir, error

[Matthew Galati]

> >> The comment was about the workaround. Instead of fiddling with 
> >> OsiCpx, it is simpler to create the empty solver interface and let 
> >> the user set whatever he wants. He will have to do the work to set 
> >> all fields appropriately.
> >
> > The problem with top-posting is, it's hard to tell what 
> responses go 
> > with what comments.  But somewhere along the thread, there was a 
> > comment about sacrificing efficiency in the computation of 
> Ax^*.  If 
> > you can't ask the solver directly, you are stuck with that 
> problem in any solution.
> 
> I was answering to Matt.
> 
> If the user wants to set the solution and the cut generator 
> uses the row activity, the latter has to be computed. The 
> user must be willing to invest the time for doing that and 
> there is no loss of efficiency.
> From what I unserstood, Matt now recomputes the row activity 
> even when it is already available, and that is a waste of 
> time. This would not happen if the "empty" solver interface 
> was available.
> 
> Francois


I'll put together a basic empty OSI class this weekend and see how it works out with CGL. I need it for my work anyway. Then, you can choose to include it or no with the current OSI distribution.

Do you want it called OsiEmpty? 

Other candidates:
 OsiRaw
 OsiNoSolver
 OsiTwinkleToes
 OsiDumb

There are certain CGLs that it can't work with -- like Gomory.  I'll have to think about how to handle that. If the CGLs have good error checking, this shouldn't be a problem. For example, if CglGomory asks Osi for a LP model ptr, OsiEmpty will have to return NULL. In that case CglGomory should give up and say, I can't generate Gomory cuts.

Matt