Distributed Gradient-Regularized Newton Method: Scheduled Consensus and O(epsilon^{-1}) Global Iteration Complexity

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Main Authors: Hu, Wei, Xie, Pengcheng, Yuan, Ya-Xiang, Zhang, Li
Format: Preprint
Published: 2026
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_version_ 1866910235051950080
author Hu, Wei
Xie, Pengcheng
Yuan, Ya-Xiang
Zhang, Li
author_facet Hu, Wei
Xie, Pengcheng
Yuan, Ya-Xiang
Zhang, Li
contents We propose DisGrem, a fully decentralized second-order method for convex consensus optimization over networks. Each agent solves a local Newton system with vanishing gradient-norm regularization and an eigenvalue-shift stabilizer, communicating through a two-stage gossip-mixing mechanism. We introduce a reference-step framework that reduces the network-wide update to an inexact centralized regularized Newton step, replacing the static Hessian-heterogeneity assumptions of prior work with an increment-based dispersion analysis that imposes no irreducible accuracy floor. Under a bounded-iterates assumption, after a burn-in phase whose order is controlled by the scheduled consensus accuracy, the post-burn-in phase achieves an O(epsilon^{-1}) iteration complexity for driving the gradient norm below epsilon, matching the centralized regularized Newton rate without line search or stepsize tuning. For a logarithmic schedule with p >= 3, the total iteration complexity remains O(epsilon^{-1}). For a fixed connected network, this yields O(epsilon^{-1} log(1/epsilon)) neighbor communication rounds, with explicit spectral-gap dependence O((1-rho)^{-1} epsilon^{-1} log(1/epsilon)) as rho approaches 1. Under strong convexity and a relative tracking-accuracy condition, we further establish conditional local superlinear convergence of order 3/2. In our nine-problem benchmark suite, the DisGrem family attains relF <= 10^{-6} on every test instance, while the tested baselines stagnate or diverge on at least one problem.
format Preprint
id arxiv_https___arxiv_org_abs_2605_19396
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Distributed Gradient-Regularized Newton Method: Scheduled Consensus and O(epsilon^{-1}) Global Iteration Complexity
Hu, Wei
Xie, Pengcheng
Yuan, Ya-Xiang
Zhang, Li
Optimization and Control
90C25, 90C30, 65K05, 68W15
We propose DisGrem, a fully decentralized second-order method for convex consensus optimization over networks. Each agent solves a local Newton system with vanishing gradient-norm regularization and an eigenvalue-shift stabilizer, communicating through a two-stage gossip-mixing mechanism. We introduce a reference-step framework that reduces the network-wide update to an inexact centralized regularized Newton step, replacing the static Hessian-heterogeneity assumptions of prior work with an increment-based dispersion analysis that imposes no irreducible accuracy floor. Under a bounded-iterates assumption, after a burn-in phase whose order is controlled by the scheduled consensus accuracy, the post-burn-in phase achieves an O(epsilon^{-1}) iteration complexity for driving the gradient norm below epsilon, matching the centralized regularized Newton rate without line search or stepsize tuning. For a logarithmic schedule with p >= 3, the total iteration complexity remains O(epsilon^{-1}). For a fixed connected network, this yields O(epsilon^{-1} log(1/epsilon)) neighbor communication rounds, with explicit spectral-gap dependence O((1-rho)^{-1} epsilon^{-1} log(1/epsilon)) as rho approaches 1. Under strong convexity and a relative tracking-accuracy condition, we further establish conditional local superlinear convergence of order 3/2. In our nine-problem benchmark suite, the DisGrem family attains relF <= 10^{-6} on every test instance, while the tested baselines stagnate or diverge on at least one problem.
title Distributed Gradient-Regularized Newton Method: Scheduled Consensus and O(epsilon^{-1}) Global Iteration Complexity
topic Optimization and Control
90C25, 90C30, 65K05, 68W15
url https://arxiv.org/abs/2605.19396