[SCIP] Strategies for Tuning Parameters in MILP problems & Pyomo compatibility

[Stefan Vigerske]

Hi,

On 6/10/22 05:25, aiman social wrote:
> Dear SCIP team,
> 
> I am currently working on an MILP scheduling problem using SCIP (with
> python Pyomo framework).
> I’m hoping to get some clarity on the following questions (or if there are
> docs for reference do let me know).
> 
> Using Pyomo framework, SCIP 6.0.0 does not seem to report back the final
> “dualbound” and “primalbound”. Is this expected?
> I'm currently reading the gap results based on the SCIP terminal print out.

Pyomo does not have its own native interface to SCIP, but instead relies 
on SCIP's AMPL interface. It is therefore limited to the information 
that can be passed via AMPL in- and output files. As far as I know, the 
AMPL solution file does not provide facilities to report primal or dual 
bounds. For the primal bound, you can obviously evaluate the objective 
function on a returned solution, if any and feasible, but for the dual 
bound, it seems to be indeed expected that you parse the solvers log.

Stefan