This modified example also demonstrates a few features that are available only in the Callable Library and Concert Technology, not in the Interactive Optimizer:

Preferences in the Conflict Refiner

You can assign preference to members of a conflict. In most cases there is no advantage to assigning unique preferences, but if you know something about your model that suggests assigning an ordering to certain members, you can do so.

Groups in the Conflict Refiner

You can organize constraints and bounds into one or more groups in a conflict. A group is a set of constraints or bounds that must be considered together; that is, if one member of a group is designated by the conflict refiner to be a necessary in a minimal conflict, then the entire group will be part of the conflict.

by the following lines to declare a group of the constraints expressing skill requirements:

         infeas.add(rng[0]);
         IloAnd skills(env);
         skills.add(rng[1]);
         skills.add(rng[2]);
         skills.add(rng[3]);
         infeas.add(skills);
         for (IloInt i = 4; i<rng.getSize(); i++) {
           infeas.add(rng[i]);
         }

(This particular modification is specific to this simplified resource allocation model and thus would not make sense in some other infeasible model you might run with the modified ilomipex2.cpp application.)

After that modification, the cost constraint and the constraints indexed 4 through 10 are treated individually (that is, normally) as before. The three constraints indexed 1 through three are combined into a skills constraint through the IloAnd operator, and added to the infeasible set.

Individual preferences are not assigned to any of these members in this example, but you could assign preferences if they express your knowledge of the problem.

After this modification to group the skill constraints, a minimal conflict is reported like this, with the skill constraints grouped inseparably:

Conflict :
Proved  : IloAnd and36 = {
c2( 2.1 <= ( x1 + x2 + 0.8 * x3 + 0.6 * x4 + 0.4 * x5 ) ) 
c3( 1.2 <= ( x6 + 0.9 * x7 + 0.5 * x8 ) ) 
c4( 0.8 <= ( x9 + 0.9 * x10 ) ) }

Proved  : c8( ( x2 + x3 + x4 + x5 )  <= 0)