Deprecated as of Analytica 4.3. Renamed to OptFindIIS.


Finds an Irreducibly Infeasile Subset of Constraints in a linear program defined using LpDefine.

An Irreducibly Infeasibe Subset (IIS) of constraints is a subset of your constraints which contains no feasible solution, but which has the property that if any single constraint is removed, there will be feasible solutions. Thus, it is a minimal set of conflicting constraints.

When LpStatusNum returns 5, it indicates that there are no feasible solutions -- that the set of constraints are contradictory. This function is useful for locating the source of the contradiction.

When called with a single parameter as shown above, a subset of the Constraints index is returned. If any constraint in that subset were to be eliminated, the resulting set of constraints would be feasible.

Variable Bound reduction

LpFindIIS(lp; newLp: optional boolean)

It is possible also to reduce the lower and upper variable bounds, in addition to the constraints, to find a more constrained IIS. This is accomplished by specifying an optional parameter, «newLp», to be true, e.g.:

LpFindIIS(myLp, newLp: true)

When the «newLp» parameter is specified as true, a new linear program object instance is created and returned. The components of this LP can be accessed using the SolverInfo function, e.g.:

SolverInfo(item: "Constraints", lp:my Lp)
SolverInfo(item: "lb", lp: myLp)
SolverInfo(item: "ub", lp: myLp)

The LP returned is infeasible, but if any single remaining variable bound, or any single constraint, were to be removed, the resulting LP would be feasible.


Introduced in Analytica 4.0.

Deprecated as of Analytica 4.3. Renamed to OptFindIIS.

See Also


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