Halpern Iteration Achieves Õ(ε⁻¹ᐟᵖ) pth-Order Oracle Complexity for Monotone Variational Inequalities

Lesi Chen, Xinliang Zhang, Hengyu Wang, Chengchang Liu, Yongchao Chen, Jingzhao Zhang

Under the paper’s pth-order smoothness and oracle assumptions, the final Halpern-based method for smooth monotone variational inequalities attains residual rate Õ(T^(−p)), or Õ(ε^(−1/p)) oracle complexity.

Sources for this record

What was already known

Monteiro and Svaiter's second-order monotone-VI rate was O(T^(−3/2)), with a general pth-order rate O(T^(−(p+1)/2)); a more recent faster rate applied to the narrower convex-concave minimax class. The optimal general monotone-VI complexity for p≥2 remained open.

AI involvement AI-centered

The researchers posed the faster-rate conjecture. GPT 5.6 Sol supplied an initial proof and resolvent subsolver; Lesi Chen, Xinliang Zhang, Chengchang Liu and Jingzhao Zhang verified the result, and the team simplified the final algorithm.

GPT 5.6 Sol supplied the first proof of the team's conjectured faster rate, while the human researchers posed the target, checked it and simplified the final algorithm.

Importance Notable

Improves the known higher-order convergence exponent for general smooth monotone variational inequalities.

Limitations

This is a general monotone-VI rate under the stated oracle assumptions; no matching lower bound establishes optimality. Claude’s earlier O(T^(−(p−1))) method is a separate intermediate result.

Technical verification Formal (human)

The paper explicitly names four human authors who verified the AI-found results and provides the initial AI algorithm and analysis beside the simplified final proof. This is source-reported human proof verification; no machine formalization or exact certificate is documented.

Formal checking

The paper explicitly names four human authors who verified the AI-found results and provides the initial AI algorithm and analysis beside the simplified final proof. This is source-reported human proof verification; no machine formalization or exact certificate is documented.

Checker
Lesi Chen, Xinliang Zhang, Chengchang Liu and Jingzhao Zhang
Scope
The Õ(T^(−p)) higher-order monotone-VI rate and its proof, developed with GPT 5.6 Sol
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

The human authors describe the Halpern iteration, resolvent subproblem and higher-order generalization, and explicitly simplify the AI's triple-loop method.

Correction and publication history

2026-10-18 · publication

GPT 5.6 Sol found an initial proof of the faster rate; the authors verified and simplified it.

Read this published revision