A Scalable Gradient-Based Optimization Framework for Sparse Minimum-Variance Portfolio Selection

Fuente: arXiv
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Auteurs principaux: Moka, Sarat, Quiroz, Matias, Asimit, Vali, Muller, Samuel
Format: Preprint
Publié: 2025
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author Moka, Sarat
Quiroz, Matias
Asimit, Vali
Muller, Samuel
author_facet Moka, Sarat
Quiroz, Matias
Asimit, Vali
Muller, Samuel
contents Portfolio optimization involves selecting asset weights to minimize a risk-reward objective, such as the portfolio variance in the classical minimum-variance framework. Sparse portfolio selection extends this by imposing a cardinality constraint: only $k$ assets from a universe of $p$ may be included. The standard approach models this problem as a mixed-integer quadratic program and relies on commercial solvers to find the optimal solution. However, the computational costs of such methods increase exponentially with $k$ and $p$, making them too slow for problems of even moderate size. We propose a fast and scalable gradient-based approach that transforms the combinatorial sparse selection problem into a constrained continuous optimization task via Boolean relaxation, while preserving equivalence with the original problem on the set of binary points. Our algorithm employs a tunable parameter that transmutes the auxiliary objective from a convex to a concave function. This allows a stable convex starting point, followed by a controlled path toward a sparse binary solution as the tuning parameter increases and the objective moves toward concavity. In practice, our method matches commercial solvers in asset selection for most instances and, in rare instances, the solution differs by a few assets whilst showing a negligible error in portfolio variance.
format Preprint
id arxiv_https___arxiv_org_abs_2505_10099
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Scalable Gradient-Based Optimization Framework for Sparse Minimum-Variance Portfolio Selection
Moka, Sarat
Quiroz, Matias
Asimit, Vali
Muller, Samuel
Machine Learning
Optimization and Control
Portfolio Management
Portfolio optimization involves selecting asset weights to minimize a risk-reward objective, such as the portfolio variance in the classical minimum-variance framework. Sparse portfolio selection extends this by imposing a cardinality constraint: only $k$ assets from a universe of $p$ may be included. The standard approach models this problem as a mixed-integer quadratic program and relies on commercial solvers to find the optimal solution. However, the computational costs of such methods increase exponentially with $k$ and $p$, making them too slow for problems of even moderate size. We propose a fast and scalable gradient-based approach that transforms the combinatorial sparse selection problem into a constrained continuous optimization task via Boolean relaxation, while preserving equivalence with the original problem on the set of binary points. Our algorithm employs a tunable parameter that transmutes the auxiliary objective from a convex to a concave function. This allows a stable convex starting point, followed by a controlled path toward a sparse binary solution as the tuning parameter increases and the objective moves toward concavity. In practice, our method matches commercial solvers in asset selection for most instances and, in rare instances, the solution differs by a few assets whilst showing a negligible error in portfolio variance.
title A Scalable Gradient-Based Optimization Framework for Sparse Minimum-Variance Portfolio Selection
topic Machine Learning
Optimization and Control
Portfolio Management
url https://arxiv.org/abs/2505.10099