[Help-glpk] Re: Add new rows in a branch and cut resolution with presolve enabled

[Xypron]

Hello David,

please, register for the GLPK help list if you want your mail to be 
received.
See http://lists.gnu.org/mailman/listinfo/help-glpk

There is no function in the API to add rows to the original problem.

You can find the internal function used for pre- and postprocessing in
function preprocess_and_solve_mip in glpk-4.45/src/glpapi09.c.

I suggest you simplify your problem formulation such that you
can do without preprocessor.

The preprocessor can be switched off using the flag presolve in
structure glp_iocp. See glpk-4.45/doc/glpk.pdf.

Best regards

Xypron


 wrote:
>      I suppose that it´s a common problem; we are using an algorithm that
> foolows a strategy based on Bender´s idea for solving a bilevel problem
> (max-min). We obtain a partial resolution of the problem using branch&cut,
> we test a set of restrictions and if any of this restrictions (a condition
> over the objective value of a min problem) is violated we obtain, from the
> dual problem, a new restriction to add to the master problem. We iterate
> until
>
>      Our problem is that we can´t enable the presolver on the master problem
> because it changes the internal representation of the problem and we can´t
> add new rows (or make any simplification of the master problem; i.e row or
> column cleaning). Is there any way, in the GLPK API, to transform from and
> to internal problem representation?
>
>      Thanks in advance, David Pérez.
>
>
>
>