Abstract
In this paper, we consider a simple bilevel program where the lower level program is a nonconvex minimization problem with a convex set constraint and the upper level program has a convex set constraint. By using the value function of the lower level program, we reformulate the bilevel program as a single level optimization problem with a nonsmooth inequality constraint and a convex set constraint. To deal with such a nonsmooth and nonconvex optimization problem, we design a smoothing projected gradient algorithm for a general optimization problem with a nonsmooth inequality constraint and a convex set constraint. We show that, if the sequence of penalty parameters is bounded then any accumulation point is a stationary point of the nonsmooth optimization problem and, if the generated sequence is convergent and the extended Mangasarian-Fromovitz constraint qualification holds at the limit then the limit point is a stationary point of the nonsmooth optimization problem. We apply the smoothing projected gradient algorithm to the bilevel program if a calmness condition holds and to an approximate bilevel program otherwise. Preliminary numerical experiments show that the algorithm is efficient for solving the simple bilevel program.
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The authors are grateful to the two anonymous referees for their helpful comments and suggestions.
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The first and second author’s work was supported in part by NSFC Grant #11071028. The third author’s work was supported in part by NSERC.
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Lin, GH., Xu, M. & Ye, J.J. On solving simple bilevel programs with a nonconvex lower level program. Math. Program. 144, 277–305 (2014). https://doi.org/10.1007/s10107-013-0633-4
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DOI: https://doi.org/10.1007/s10107-013-0633-4
Keywords
- Bilevel program
- Value function
- Partial calmness
- Smoothing function
- Gradient consistent property
- Integral entropy function
- Smoothing projected gradient algorithm