Convex Optimization with Nested Evolving Feasible Sets (CONES) under Time-Varying Loss Functions

arXiv cs.LG Papers

Summary

This paper extends CONES to time-varying loss functions, showing bounds for regret and movement cost using projected proximal algorithms in convex optimization.

arXiv:2609.11207v1 Announce Type: new Abstract: Convex Optimization with Nested Evolving Feasible Sets (CONES)} was introduced in \cite{CONESVaze} where the objective function \(f\) remains fixed but the feasible region evolves over time as a nested sequence \(S_1 \supseteq S_2 \supseteq \cdots \supseteq S_T\). The goal of an online algorithm is to simultaneously minimize the regret with respect to hindsight static optimal benchmark and the total movement cost $M_\cA(T)$ while ensuring feasibility at all times. CONES is an optimization-oriented generalization of the well-known \emph{nested convex body chasing} (NCBC). In this paper, we extend CONES to allow for loss functions $f_t'$s to also change over time. When all loss functions are convex, we show that the projected proximal algorithm achieves $O(T^{1-\beta}), O(T^\beta)$ simultaneous regret and movement cost, respectively, for any $\beta \in [0,1)$, over a time horizon of $T$. We also show that any {\it weakly adaptive} online algorithm with $O(T^\beta)$ regret has a movement cost of $\Omega\left(T^{\frac{1-\beta}{2}}\right)$ for any $\beta \in [0,1)$. When all loss functions are strongly convex, we show that the projected proximal algorithm simultaneously achieves $O(1)$ regret and a movement cost of $O(\log T)$. To complement this, we show that any online algorithm with sublinear {\it anytime} regret has a movement cost of $\Omega\left(\log T\right)$.
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# Convex Optimization with Nested Evolving Feasible Sets (CONES) under Time-Varying Loss Functions
Source: [https://arxiv.org/abs/2609.11207](https://arxiv.org/abs/2609.11207)
[View PDF](https://arxiv.org/pdf/2609.11207)[HTML \(experimental\)](https://arxiv.org/html/2609.11207v1)

> Abstract:Convex Optimization with Nested Evolving Feasible Sets \(CONES\)\} was introduced in \\cite\{CONESVaze\} where the objective function \\\(f\\\) remains fixed but the feasible region evolves over time as a nested sequence \\\(S\_1 \\supseteq S\_2 \\supseteq \\cdots \\supseteq S\_T\\\)\. The goal of an online algorithm is to simultaneously minimize the regret with respect to hindsight static optimal benchmark and the total movement cost $M\_\\cA\(T\)$ while ensuring feasibility at all times\. CONES is an optimization\-oriented generalization of the well\-known \\emph\{nested convex body chasing\} \(NCBC\)\. In this paper, we extend CONES to allow for loss functions $f\_t'$s to also change over time\. When all loss functions are convex, we show that the projected proximal algorithm achieves $O\(T^\{1\-\\beta\}\), O\(T^\\beta\)$ simultaneous regret and movement cost, respectively, for any $\\beta \\in \[0,1\)$, over a time horizon of $T$\. We also show that any \{\\it weakly adaptive\} online algorithm with $O\(T^\\beta\)$ regret has a movement cost of $\\Omega\\left\(T^\{\\frac\{1\-\\beta\}\{2\}\}\\right\)$ for any $\\beta \\in \[0,1\)$\. When all loss functions are strongly convex, we show that the projected proximal algorithm simultaneously achieves $O\(1\)$ regret and a movement cost of $O\(\\log T\)$\. To complement this, we show that any online algorithm with sublinear \{\\it anytime\} regret has a movement cost of $\\Omega\\left\(\\log T\\right\)$\.

## Submission history

From: Rahul Vaze \[[view email](https://arxiv.org/show-email/db8087f8/2609.11207)\] **\[v1\]**Thu, 10 Sep 2026 08:13:27 UTC \(22 KB\)

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