ResearchResearch paperTraining & Scaling · Reinforcement Learning1 source · Oct 9, 2026

Geometry-Aware Multi-Objective Optimization: Norm-Constrained Oracles with Entropic Weight Updates

We analyze a single-loop multi-objective method combining a norm-constrained linear minimization oracle with entropic updates of task weights.

Key points

  • Multiple-gradient descent is typically formulated in Euclidean geometry, whereas matrix-aware optimizers use directions induced by other norms.
  • For any finite-dimensional norm pair, we establish an $O(T^{-1/2})$ ergodic stationarity rate in the deterministic setting, deriving the required trajectory gradient bound from smoothness and lower-boundedness in the unregularized case.
  • With stochastic gradients and a bounded-gradient assumption, one persistent blended-gradient momentum buffer yields an $O(T^{-1/4})$ rate whose leading term has no explicit dependence on the number of tasks.
  • We also establish static regret for the inner weighting objective on arbitrary bounded gradient sequences and, with entropy regularization and a weight floor, iteration-wise inner-gap control after burn-in while retaining ergodic stationarity, conditional on a trajectory gradient bound.

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