Abstract
We give new characterizations for the subdifferential of the supremum of an arbitrary family of convex functions, dropping out the standard assumptions of compactness of the index set and upper semi-continuity of the functions with respect to the index (J. Convex Anal. 26, 299–324, 2019). We develop an approach based on the compactification of the index set, giving rise to an appropriate enlargement of the original family. Moreover, in contrast to the previous results in the literature, our characterizations are formulated exclusively in terms of exact subdifferentials at the nominal point. Fritz–John and KKT conditions are derived for convex semi-infinite programming.
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References
Brøndsted, A.: On the subdifferential of the supremum of two convex functions. Math. Scand. 31, 225–230 (1972)
Chieu, N.H., Jeyakumar, V., Li, G., Mohebi, H.: Constraint qualifications for convex optimization without convexity of constraints: new connections and applications to best approximation. Eur. J. Oper. Res. 265, 19–25 (2018)
Correa, R., Hantoute, A., López, M.A.: Weaker conditions for subdifferential calculus of convex functions. J. Funct. Anal. 271, 1177–1212 (2016)
Correa, R., Hantoute, A., López, M.A.: Towards supremum-sum subdifferential calculus free of qualification conditions. SIAM J. Optim. 26, 2219–2234 (2016)
Correa, R., Hantoute, A., López, M.A.: Valadier-like formulas for the supremum function I. J. Convex Anal. 25, 1253–1278 (2018)
Correa, R., Hantoute, A., López, M.A.: Moreau–rockafellar type formulas for the subdifferential of the supremum function. SIAM J. Optim. 29, 1106–1130 (2019)
Correa, R., Hantoute, A., López, M.A.: Valadier-like formulas for the supremum function II: the compactly indexed case. J. Convex Anal. 26, 299–324 (2019)
Dinh, N., Goberna, M.A., López, M.A.: From linear to convex systems: consistency, Farkas’ lemma and applications. J. Convex Anal. 13, 113–133 (2006)
Dutta, J., Lalitha, C.S.: Optimality conditions in convex optimization revisited. Optim. Lett. 7, 221–229 (2013)
Ekeland, I., Témam, R.: Convex Analysis and Variational Problems. North-holland & American Elsevier, Amsterdam (1976)
Goberna, M.A., López, M.A.: Linear Semi-infinite Optimization. J. Wiley, Chichester (1998)
Hantoute, A.: Subdifferential set of the supremum of lower semi-continuous convex functions and the conical hull property. Top 14, 355–374 (2006)
Hantoute, A., López, M. A.: A complete characterization of the subdifferential set of the supremum of an arbitrary family of convex functions. J. Convex Anal. 15, 831–858 (2008)
Hantoute, A., López, M.A., Zălinescu, C.: Subdifferential calculus rules in convex analysis: a unifying approach via pointwise supremum functions. SIAM J. Optim. 19, 863–882 (2008)
Hiriart-Urruty, J.-B.: Convex analysis and optimization in the past 50 years: some snapshots. In: Demyanov, V.F., Pardalos, P.M., Batsyn, M (eds.) Constructive Nonsmooth Analysis and Related Topics. Springer Optimization and Its Applications, vol. 87, pp 245–253. Springer, New York (2014)
Hiriart-Urruty, J.-B., Phelps, R.R.: Subdifferential calculus using ε-subdifferentials. J. Funct. Anal. 118, 154–166 (1993)
Ioffe, A.D.: A note on subdifferentials of pointwise suprema. Top 20, 456–466 (2012)
Ioffe, A.D., Levin, V.L.: Subdifferentials of convex functions. Tr. Moskov Mat. Obshch 26, 3–73 (1972). (In Russian)
Ioffe, A.D., Tikhomirov, V.H.: Theory of Extremal Problems. Studies in Mathematics and Its Applications, vol. 6. North-Holland, Amsterdam (1979)
Levin, V.L.: An application of Helly’s theorem in convex programming, problems of best approximation and related questions. Mat. Sb., Nov. Ser. 79, 250–263 (1969). Engl. Trans.: Math. USSR, Sb. 8, 235–247 (1969)
López, M.A., Volle, M.: A formula for the set of optimal solutions of relaxed minimization problems. Applications to subdifferential calculus. J. Convex Anal. 17, 1057–1075 (2010)
Munkres, J.: Topology, 2nd edn. Prentice Hall, Upper Saddle River (2000)
Pschenichnyi, B.N.: Convex programming in a normalized space. Kibernetika 5, 46–54 (1965). (Russian); Engl. Trans.: Cybernetics 1, 46–57 (1965)
Rockafellar, R.T., Brøndsted, A.: On the subdifferentiability of convex functions. Proc. Am. Math. Soc. 16, 605–611 (1965)
Rockafellar, R.T.: Convex Analysis. Princeton University Press, Princeton (1970)
Rockafellar, R.T.: Directionally Lipschitzian functions and subdifferential calculus. Proc. Lond. Math. Soc. 39, 331–355 (1979)
Solov’ev, V.N.: The subdifferential and the directional derivatives of the maximum of a family of convex functions. Izvestiya RAN: Ser. Mat. 65, 107–132 (2001)
Thibault, L.: Sequential convex subdifferential calculus and sequential Lagrange multipliers. SIAM J. Control Optim. 35, 1434–1444 (1997)
Tikhomirov, V. M.: Analysis II: convex analysis and approximation theory. In: Gamkrelidze, R.V. (ed.) Encyclopaedia of Mathematical Sciences, vol. 14. Springer, Berlin (1990)
Valadier, M.: Sous-différentiels d’une borne supérieure et d’une somme continue de fonctions convexes. C. R. Acad. Sci. Paris Sé,r. A-B 268, A39–A42 (1969)
Zălinescu, C.: Convex Analysis in General Vector Spaces. World Scientific, River Edge (2002)
Acknowledgements
Research supported by CONICYT (Fondecyt 1190012 and 1190110), Proyecto/Grant PIA AFB-170001, MICIU of Spain and Universidad de Alicante (Grant Beatriz Galindo BEA- GAL 18/00205), and Research Project PGC2018-097960-B-C21 from MICINN, Spain. The research of the third author is also supported by the Australian ARC - Discovery Projects DP 180100602.
The authors wish to thank the referee for the valuable comments and suggestions which have contributed to improve the first version of this paper.
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Dedicated by his coauthors to Prof. Marco A. López on his 70th birthday.
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Correa, R., Hantoute, A. & López, M.A. Subdifferential of the Supremum via Compactification of the Index Set. Vietnam J. Math. 48, 569–588 (2020). https://doi.org/10.1007/s10013-020-00403-5
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DOI: https://doi.org/10.1007/s10013-020-00403-5
Keywords
- Supremum of convex functions
- Subdifferentials
- Stone–Čech compactification
- Convex semi-infinite programming
- Optimality conditions