BASBLib - A Library of Bilevel Test Problems

A growing collection of bilevel problems

Quadratic-Quadratic bilevel problem from [Yezza, 1996]


Optimal solution

Objective values Solution points
F* = 1.5 x* = 0.25
f* = -2.5 y* = 0.0

Sources where this problem occurs

Original source:

Other sources:

Description of the problem in the AMPL format

var x >= 0, <= 1;         # Outer variable
var y >= 0, <= 1;         # Inner variable
var l{1..5} >= 0, <= 10;  # KKT Multipliers

minimize outer_obj: -(4*x - 3)*y + 2*x + 1;  # Outer objective

subject to
# Inner objective:
    inner_obj: -(1 - 4*x)*y - 2*x -2 = 0;
# KKT conditions:
    stationarity:      4*x - 1 = 0;
    complementarity_1: l[1]*y = 0;
    complementarity_2: l[2]*(y - 1) = 0;

References