Initializing help system before first use

# problem.getIISData

Purpose
Returns information for an Irreducible Infeasible Set: size, variables and constraints (row and column vectors), and conflicting sides of the variables. For pure linear problems there is also information on duals, reduced costs and isolations.
Topic areas
Infeasibility, Optimizer
Synopsis
`rowind, colind, contype, bndtype, duals, djs, isolationrows, isolationcols = problem.getIISData(iis)`
Argument

iis: int | The ordinal number of the IIS to get data for.

Return value

rowind: list[int] | Indices of rows/sets/piecewise linear constraints/general constraints in the IIS.
colind: list[int] | Indices of bounds (columns) in the IIS.
contype: list[str] | Sense of rows in the IIS:
L | for less or equal row;
G | for greater or equal row.
E | for an equality row (for a non LP IIS);
1 | for a SOS1 row;
2 | for a SOS2 row;
W | for a piecewise linear constraint;
X | for a general constraint;
I | for an indicator row.
bndtype: list[str] | Sense of bound in the IIS:
U | for upper bound;
L | for lower bound.
F | for fixed columns (for a non LP IIS);
B | for a binary column;
I | for an integer column;
P | for a partial integer columns;
S | for a semi-continuous column;
R | for a semi-continuous integer column.
duals: list[float] | The dual multipliers associated with the rows.
djs: list[float] | The dual multipliers (reduced costs) associated with the bounds.
isolationrows: list[str] | The isolation status of the rows:
-1 | if isolation information is not available for row (run iis isolations);
0 | if row is not in isolation;
1 | if row is in isolation.
isolationcols: list[str] | The isolation status of the bounds:
-1 | if isolation information is not available for column (run iis isolations);
0 | if column is not in isolation;
1 | if column is in isolation.

Further information
1. IISs are numbered from 1 to NUMIIS. Index number 0 refers to the IIS approximation.
2. For the initial IIS approximation of linear problems ( iis = 0) the number of rows and columns with a nonzero Lagrange multiplier (dual/reduced cost respectively) are returned. Please note that, in such cases, it might be necessary to call problem.IISStatus to retrieve the necessary size of the return arrays.
3. If there are special ordered sets, piecewise linear constraints or general constraints in the IIS, their number is included in the rowind array.
4. For non LP IISs, some column indices may appear more than once in the colind array, for example an integrality and a bound restriction for the same column.
5. Duals, reduced cost and isolation information are not available for nonlinear IIS problems, and for those the arrays are filled with zero values if they are provided.
Related topics
problem.IISAll, problem.clearIIS, problem.firstIIS, problem.IISIsolations, problem.nextIIS, problem.IISStatus, problem.writeIIS the Optimizer Reference Manual.
Parent Topic Xpress problem object methods

© 2001-2026 Fair Isaac Corporation. All rights reserved. This documentation is the property of Fair Isaac Corporation (“FICO”). Receipt or possession of this documentation does not convey rights to disclose, reproduce, make derivative works, use, or allow others to use it except solely for internal evaluation purposes to determine whether to purchase a license to the software described in this documentation, or as otherwise set forth in a written software license agreement between you and FICO (or a FICO affiliate). Use of this documentation and the software described in it must conform strictly to the foregoing permitted uses, and no other use is permitted.