Optimisation robuste | EPFL Graph Search

L'optimisation robuste est une branche de l'optimisation mathématique qui cherche à résoudre un problème d'optimisation en prenant en compte les différentes sources d'incertitude de celui-ci. Histoire Les origines de l'optimisation robuste remontent aux débuts de la théorie de la décision moderne dans les années 1950. Des « analyses des cas les plus défavorables » ont été réalisées pour faire face aux fortes incertitudes. L'optimisation robuste devient dans les années 1970 une discipline à elle-seule avec des applications dans des domaines tels que la recherche opérationnelle, la théorie du contrôle, les statistiques, l'économie… Exemple
Considérons le problème de type optimisation linéaire suivant : \max_{x,y} \ {3x + 2y} \ \ \mathrm { s.c. }\ \ \left{\begin{array}{l} cx + dy \le 10, \forall (c,d)\in P ; \ x,y\ge 0 \end{array}\right. où P est un sous-ensemble de \mathbb{R}^{2}. La ligne cx + dy \le 10,

Distributionally Robust Optimization with Markovian Data

Daniel Kuhn, Mengmeng Li, Tobias Sutter

We study a stochastic program where the probability distribution of the uncertain problem parameters is unknown and only indirectly observed via finitely many correlated samples generated by an unknown Markov chain with d states. We propose a data-driven distributionally robust optimization model to estimate the problem’s objective function and optimal solution. By leveraging results from large deviations theory, we derive statistical guarantees on the quality of these estimators. The underlying worst-case expectation problem is nonconvex and involves O(d^2) decision variables. Thus, it cannot be solved efficiently for large d. By exploiting the structure of this prob- lem, we devise a customized Frank-Wolfe algorithm with convex direction-finding subproblems of size O(d). We prove that this algorithm finds a stationary point efficiently under mild conditions. The efficiency of the method is predicated on a dimensionality reduction enabled by a dual reformulation. Numerical experiments indicate that our approach has better computational and statistical properties than the state-of-the-art methods.

2021

Multi-Period Portfolio Optimization: Translation of Autocorrelation Risk to Excess Variance

Byung-Geun Choi, Napat Rujeerapaiboon

Growth-optimal portfolios are guaranteed to accumulate higher wealth than any other investment strategy in the long run. However, they tend to be risky in the short term. For serially uncorrelated markets, similar portfolios with more robust guarantees have been recently proposed. This paper extends these robust portfolios by accommodating non-zero autocorrelations that may reflect investors' beliefs about market movements. Moreover, we prove that the risk incurred by such autocorrelations can be absorbed by modifying the covariance matrix of asset returns.

2016

Robust Portfolio Optimization

Zheng Wei Yap

Since the 2008 Global Financial Crisis, the financial market has become more unpredictable than ever before, and it seems set to remain so in the forseeable future. This means an investor faces unprecedented risks, hence the increasing need for robust portfolio optimization to protect them against uncertainty, which is potentially devastating if unattended yet ignored in the classical Markowitz model, whose another deficiency is the absence of higher moments in its assumption of the distribution of asset returns. We establish an equivalence between the Markowitz model and the portfolio return value-at-risk optimization problem under multivariate normality of asset returns, so that we can add these excluded features into the former implicitly by incorporating them into the latter. We also provide a probabilistic smoothing spline approximation method and a deterministic model within the location-scale framework under elliptical distribution of the asset returns to solve the robust portfolio return value-at-risk optimization problem. In particular for the deterministic model, we introduce a novel eigendecomposition uncertainty set which lives in the positive definite space for the scale matrix without compromising on the computational complexity and conservativeness of the optimization problem, invent a method to determine the size of the involved uncertainty sets, test it out on real data, and explore its diversification properties. Although the value-at-risk has been the standard risk measure adopted by the banking and insurance industry since the early nineties, it has since attracted many criticisms, in particular from McNeil et al. (2005) and the Basel Committee on Banking Supervision in 2012, also known as Basel 3.5. Basel 4 even suggests a move away from the what" value-at-risk to the what-if" conditional value-at-risk' measure. We shall see that the former may be replaced with the latter or even other risk measures in our formulations easily.

EPFL2017

Robust Portfolio Optimization

Zheng Wei Yap

EPFL2017