infeasible or unbounded situation after zero iteration

[m.jah...@gmail.com]

Hi,
I faced with a warning, that says Warning: After zero iterations the preprocessor of CPLEX 12.3 concluded that SubProblemf3 is infeasible or unbounded.Two points are important here. First, the constraints that are related to this problem are the subset of ALLCONSTRAINTS, and when I solve this problem with ALLCONSTRAINTS no error will occur!!!!. Second, there is nothing in the listing file (after running this procedure!!!)

If you have any good idea or the same experience please tell me

Thanks

[Guido Diepen]

Hi,

you will only see the constraint listing  in the listing file if you have instructed AIMMS to print the listing file via the project options. Please find any of my earlier posts on this google group for instructions on how to setup AIMMS such that it will print the listing file.

Guido Diepen

AIMMS Specialist

[Marcel Hunting]

Hi,

It seems that the problem is unbounded if you only use the subset of AllConstraints. If you switch off the CPLEX option 'presolve' then CPLEX will tell you whether the problem is actual infeasible or unbounded.

You should set the option 'Constraint Listing' to 'At every solve' (or 'At first solve') to get a constraint listing printed in case the problem is unbounded.

Marcel Hunting

AIMMS Software Developer

On Wednesday, March 6, 2013 8:52:30 AM UTC+1, m.jah...@gmail.com wrote:

[m.jah...@gmail.com]

thanks , how can I switch off the CPLEX option 'presolve'?

[Dirk]

Hi,

When you say, "the constraints that are related to this problem are the subset of ALLCONSTRAINTS " I'm assuming that you're mathematical model references a subset of AllConstraints which includes all constraints in your model.

I've experienced the same thing you have because I defined my subset incorrectly.  Specifically, I forgot to include the constraints that are created from variables with definitions.  I've found the best way to address this problem was by using references to sections in the model tree when defining my subset.

In the example below,  'Section_2_Mathematical_Model' is a Section in my model tree;   'Unused_Section'   is a declaration identifier in the model tree.  The set MyModelConstraints contains all constraints (including variable definition constraints) in the section   'Section_2_Mathematical_Model', but excludes those in the   'Unused_Section'  

SET:
identifier : MyModelConstraints
subset of : AllConstraints
index : iSC
  definition : AllConstraints * Section_2_Mathematical_Model - AllConstraints * Unused_Section
   

[Guido Diepen]

Hi,

you can set this option by going to Menu > Settings > Project options > Specific Solvers > CPLEX 12.X > Preprocessing. Then select Presolve in the right screen and set the value to No.

Guido Diepen

AIMMS Specialist