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arxiv: 2605.12058 · v1 · submitted 2026-05-12 · 💻 cs.LG · cs.AI

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H\"older Policy Optimisation

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Pith reviewed 2026-05-13 05:58 UTC · model grok-4.3

classification 💻 cs.LG cs.AI
keywords Hölder meanpolicy optimizationGRPOreinforcement learninglarge language modelsgradient aggregationmathematical reasoning
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The pith

HölderPO resolves GRPO's aggregation trade-off by using a tunable Hölder mean with annealed parameter p to control gradient concentration and variance.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that fixed aggregation of token probabilities in Group Relative Policy Optimisation creates either training collapse or suboptimal performance. It shows that the Hölder mean offers continuous modulation via the parameter p, where higher values concentrate gradients on sparse signals and lower values bound variance. A dynamic annealing schedule for p adapts this balance throughout training. This leads to improved stability, convergence, and empirical results including 54.9 percent average accuracy on mathematical benchmarks and 93.8 percent success rate on ALFWorld.

Core claim

The central claim is that mapping trajectory advantages to policy updates in GRPO is limited by fixed aggregation mechanisms, but the Hölder mean unifies them and allows explicit control: larger p concentrates the gradient to amplify learning signals while smaller p strictly bounds gradient variance. Since no static p resolves the trade-off universally, dynamic annealing of p across the training lifecycle produces superior stability and performance over baselines.

What carries the argument

The Hölder mean applied to token-level probability aggregation within each trajectory, where the parameter p determines the degree of gradient concentration versus variance bounding.

Load-bearing premise

That modulating the single scalar p via annealing will reliably resolve the concentration-stability trade-off across different model sizes, tasks, and sampling budgets without introducing new failure modes.

What would settle it

A direct comparison of the annealed schedule against the best fixed p value, measured by whether the fixed version matches or exceeds the reported 54.9 percent average accuracy on the mathematical benchmarks.

Figures

Figures reproduced from arXiv: 2605.12058 by Chenyang Le, Dingli Liang, Jiachen Zhu, Jianghao Lin, Jun Wang, Lingyu Yang, Weinan Zhang, Yihang Chen, Yuxiang Chen, Zhaokai Wang, Ziqin Gong.

Figure 1
Figure 1. Figure 1: HölderPO unifies token-level aggregation under a single parameter p. The objective at the top generalises GRPO by replacing its arithmetic mean over token-level importance ratios with the Hölder mean of order p ∈ R, recovering GRPO (p = 1) and GMPO/GSPO (p → 0) as special cases. The bar chart reports accuracy on AIME24 (blue, sparse signal) and MATH500 (red, dense signal), with dashed lines marking GRPO ba… view at source ↗
Figure 2
Figure 2. Figure 2: Token-level importance ratio log ρt(θ) during training. Left and Right track the per-step upper and lower envelopes respectively. As p decreases, the upper envelope drops and the lower envelope rises, tightening the gap monotonically. Our decaying schedule p: 2→−2 (solid green) thus enables aggressive updates in the early stage and progressively converges to stable optimization in the later stage. Constant… view at source ↗
Figure 3
Figure 3. Figure 3: Entropy and gradient-norm dynamics under different Hölder exponents p. Columns: Math (Qwen2.5-Math-7B on MATH-12k) and Alfworld (Qwen2.5-1.5B). Rows: per-step policy entropy and gradient norm ∥∇L∥ (log scale on Math, linear on Alfworld). Constant-p baselines (p ∈ {+2, 0, −2}, dashed/dotted/dash-dotted) are compared with our linearly-decaying schedule p: 2→−2 (solid green). Positive p concentrates mass on h… view at source ↗
read the original abstract

Group Relative Policy Optimisation (GRPO) enhances large language models by estimating advantages across a group of sampled trajectories. However, mapping these trajectory-level advantages to policy updates requires aggregating token-level probabilities within each sequence. Relying on a fixed aggregation mechanism for this step fundamentally limits the algorithm's adaptability. Empirically, we observe a critical trade-off: certain fixed aggregations frequently suffer from training collapse, while others fail to yield satisfactory performance. To resolve this, we propose \textbf{H\"{o}lderPO}, a generalised policy optimisation framework unifying token-level probability aggregation via the H\"{o}lder mean. By explicitly modulating the parameter $p$, our framework provides continuous control over the trade-off between gradient concentration and variance bounds. Theoretically, we prove that a larger $p$ concentrates the gradient to amplify sparse learning signals, whereas a smaller $p$ strictly bounds gradient variance. Because no static configuration can universally resolve this concentration-stability trade-off, we instantiate the framework with a dynamic annealing algorithm that progressively schedules $p$ across the training lifecycle. Extensive evaluations demonstrate superior stability and convergence over existing baselines. Specifically, our approach achieves a state-of-the-art average accuracy of $54.9\%$ across multiple mathematical benchmarks, yielding a substantial $7.2\%$ relative gain over standard GRPO and secures an exceptional $93.8\%$ success rate on ALFWorld.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 2 minor

Summary. The paper proposes HölderPO as a generalization of Group Relative Policy Optimisation (GRPO) for LLM policy optimization. It replaces fixed aggregation of token-level probabilities with the Hölder mean, controlled by a scalar parameter p that trades off gradient concentration (large p) against variance bounds (small p). Theoretical claims establish the limiting behaviors of p, and a dynamic annealing schedule is introduced because no fixed p works universally. Experiments report 54.9% average accuracy on mathematical benchmarks (+7.2% relative to GRPO) and 93.8% success on ALFWorld.

Significance. If the gradient-concentration and variance-bound results are rigorously derived and the empirical gains survive proper ablations and statistical controls, the framework would supply a continuous, theoretically grounded knob for the stability-performance trade-off that appears in many group-based RL methods for LLMs. The explicit unification via Hölder means and the annealing instantiation are the primary contributions.

major comments (3)
  1. [§3] §3 (theoretical analysis): the claim that larger p concentrates the gradient to amplify sparse signals and that smaller p strictly bounds variance is asserted without the key intermediate inequalities or proof steps; the load-bearing step is the mapping from the Hölder mean definition to the advantage-weighted policy gradient, which must be shown explicitly under the GRPO group-relative advantage estimator.
  2. [Experimental section] Experimental section, results table for mathematical benchmarks: the reported 54.9% average and 7.2% relative gain lack error bars, number of random seeds, and any ablation that isolates the annealing schedule from fixed-p Hölder means or from extra hyper-parameter search; without these controls the claim that dynamic p “resolves” the trade-off cannot be distinguished from post-hoc fitting on the same evaluation suites.
  3. [§4.2] §4.2 (annealing algorithm): the specific functional form and timing of the p schedule constitute an additional free parameter whose selection procedure is not described; if this schedule was tuned on the math and ALFWorld data used for final reporting, the performance numbers are at risk of circularity and the universality claim is under-supported.
minor comments (2)
  1. [§2] The Hölder-mean formula itself should be written explicitly once (e.g., as Eq. (3)) rather than left implicit, to aid readers unfamiliar with the family.
  2. [Figures] Figure captions for training curves should state the exact p-annealing schedule used in each run.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed report. We address each major comment below and will incorporate revisions to improve the rigor and clarity of the manuscript.

read point-by-point responses
  1. Referee: [§3] §3 (theoretical analysis): the claim that larger p concentrates the gradient to amplify sparse signals and that smaller p strictly bounds variance is asserted without the key intermediate inequalities or proof steps; the load-bearing step is the mapping from the Hölder mean definition to the advantage-weighted policy gradient, which must be shown explicitly under the GRPO group-relative advantage estimator.

    Authors: We agree that the theoretical claims in §3 require more explicit intermediate steps. In the revised manuscript we will expand the section to include the full derivation: starting from the definition of the Hölder mean, we will show the explicit mapping to the advantage-weighted policy gradient under the GRPO estimator, followed by the inequalities establishing gradient concentration for large p and strict variance bounds for small p. revision: yes

  2. Referee: Experimental section, results table for mathematical benchmarks: the reported 54.9% average and 7.2% relative gain lack error bars, number of random seeds, and any ablation that isolates the annealing schedule from fixed-p Hölder means or from extra hyper-parameter search; without these controls the claim that dynamic p “resolves” the trade-off cannot be distinguished from post-hoc fitting on the same evaluation suites.

    Authors: We will revise the experimental section to report error bars computed across multiple random seeds, state the number of seeds employed, and add ablation studies that compare the dynamic annealing schedule against fixed-p Hölder means while controlling for hyper-parameter search effort. These additions will allow readers to isolate the contribution of the annealing procedure. revision: yes

  3. Referee: [§4.2] §4.2 (annealing algorithm): the specific functional form and timing of the p schedule constitute an additional free parameter whose selection procedure is not described; if this schedule was tuned on the math and ALFWorld data used for final reporting, the performance numbers are at risk of circularity and the universality claim is under-supported.

    Authors: We will expand §4.2 to give the exact functional form of the p schedule, the timing parameters, and the procedure used to select them. The schedule was chosen via preliminary runs on a held-out validation split distinct from the final reported benchmarks; we will state this explicitly and list the concrete hyper-parameters to remove any ambiguity about circularity. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected in the HölderPO derivation

full rationale

The paper's chain begins with an empirical observation of trade-offs in fixed aggregations for GRPO, introduces the Hölder mean (a pre-existing mathematical object) to unify them, derives theoretical bounds on gradient concentration for large p and variance for small p, and motivates dynamic annealing of p because no fixed value resolves the trade-off universally. None of these steps reduce by construction to the final benchmark numbers; the annealing schedule is an explicit algorithmic choice whose specific form is not shown to be equivalent to fitting on the reported math or ALFWorld results. The performance claims are presented as downstream experimental outcomes rather than tautological consequences of the inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the mathematical properties of the Hölder mean (standard) and on the empirical claim that a particular annealing schedule for p improves stability and performance (ad-hoc to the paper). No new physical entities are postulated.

free parameters (1)
  • p
    Continuous parameter of the Hölder mean that controls the aggregation; its schedule is chosen by the authors.
axioms (1)
  • standard math Hölder mean properties hold for the token-probability vectors arising in LLM policy gradients
    Invoked when claiming gradient concentration for large p and variance bounds for small p.

pith-pipeline@v0.9.0 · 5579 in / 1336 out tokens · 44164 ms · 2026-05-13T05:58:47.841499+00:00 · methodology

discussion (0)

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Reference graph

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