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strong duality

Strong duality is a condition in mathematical optimization where the optimal objective value of the primal problem equals the optimal objective value of its dual problem, resulting in a duality gap of zero. Unlike weak duality, which only guarantees that the dual problem provides a bound on the primal objective, strong duality allows practitioners to solve the dual formulation to find the exact optimal value of the original primal problem. This property holds under specific conditions, most commonly in convex optimization problems that satisfy constraint qualifications such as Slaters condition. Strong duality is central to optimization theory because it underpins the Karush-Kuhn-Tucker optimality conditions and enables efficient algorithms across convex programming, dual decomposition, and multi-objective optimization.

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A Multi-objective / Multi-task Learning Framework Induced by Pareto Stationarity

A Multi-objective / Multi-task Learning Framework Induced by Pareto Stationarity

Michinari Momma, Chaosheng Dong, Jia Liu

Why you should read this

Develops a generic multi-objective learning framework based on Pareto stationarity that incorporates user preferences and extends weighted Chebyshev optimization to discover models outperforming existing baselines in a single training run.

Multi-objective optimization (MOO) and multi-task learning (MTL) have gained much popularity with prevalent use cases such as production model development of regression / classification / ranking models with MOO, and training deep learning models with MTL. Despite the long history of research in MOO, its application to machine learning requires development of solution strategy, and algorithms have recently been developed to solve specific problems such as discovery of any Pareto optimal (PO) solution, and that with a particular form of preference. In this paper, we develop a novel and generic framework to discover a PO solution with multiple forms of preferences. It allows us to formulate a generic MOO / MTL problem to express a preference, which is solved to achieve both alignment with the preference and PO, at the same time. Specifically, we apply the framework to solve the weighted Chebyshev problem and an extension of that. The former is known as a method to discover the Pareto front, the latter helps to find a model that outperforms an existing model with only one run. Experimental results demonstrate not only the method achieves competitive performance with existing methods, but also it allows us to achieve the performance from different forms of preferences.

Added

2026-10-03