GRBModel::computeIIS()

Compute an Irreducible Inconsistent Subsystem (IIS). An IIS is a subset of the constraints and variable bounds with the following properties:

  • the subsystem represented by the IIS is infeasible, and
  • if any of the constraints or bounds of the IIS is removed, the subsystem becomes feasible.
Note that an infeasible model may have multiple IISs. The one returned by Gurobi is not necessarily one of minimal cardinality. Thus, there may exist other IISs with fewer constraints or bounds.

If an IIS computation is interrupted before completion, Gurobi will internally store the best available IIS found so far.

This method populates the IISCONSTR, IISQCONSTR, and IISGENCONSTR constraint attributes, the IISSOS SOS attribute, and the IISLB, and IISUB variable attributes. You can also obtain information about the results of the IIS computation by writing a .ilp format file (see GRBModel::write). This file contains only the IIS from the original model.

Note that this method can be used to compute IISs for both continuous and MIP models.

void computeIIS ( )

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