Documentation

Model.computeIIS()

computeIIS ( void )

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 the one with minimum cardinality; there may exist others with fewer constraints or bounds.

If an IIS computation is interrupted before completion, Gurobi will return the smallest IIS found to that point.

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 an .ilp format file (see Model.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.

Example usage:

  model.computeIIS()
  model.write("model.ilp")