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arxiv: 2606.09883 · v1 · pith:AGC5REWAnew · submitted 2026-06-03 · 💻 cs.LG · cs.AI

TD-Grokking: Learning from Zero-Reward Problems by Training-Time Decomposition

Pith reviewed 2026-06-28 06:49 UTC · model grok-4.3

classification 💻 cs.LG cs.AI
keywords zero-reward problemstraining-time decompositionreinforcement learning with verifiable rewardslanguage model reasoninghierarchical problem solvingmathematical reasoningmedical reasoning
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The pith

Recursive decomposition turns zero-reward problems into usable training signals for language models.

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

The paper aims to show that large language models can learn from problems where every reasoning attempt fails and yields zero reward. It does so by breaking each intractable root problem into a tree of smaller, self-contained subproblems that can be verified and rewarded. A sympathetic reader would care because current reinforcement learning methods stall completely on the hardest reasoning tasks, leaving no gradient for improvement. The approach is tested on mathematical and medical benchmarks where it beats standard methods. If the decomposition works, previously untrainable examples become sources of learning.

Core claim

TD-Grokking recursively decomposes intractable root problems into self-contained, verifiable subproblems, forming hierarchical trees where solvable leaves provide non-zero rewards; this converts zero-reward examples into training signals that enable the policy model to acquire the capabilities needed for the original problems.

What carries the argument

Recursive training-time decomposition that builds hierarchical trees of verifiable subproblems from each root problem.

If this is right

  • Models achieve consistent gains on mathematical and medical tasks over vanilla GRPO and prior baselines.
  • Zero-reward examples become sources of optimization signal rather than wasted computation.
  • The policy model gains the step-by-step capabilities required to solve the original intractable problems.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same decomposition tree could be reused across multiple root problems that share substructure, reducing total search cost.
  • If subproblem verification can be automated, the method might extend to domains without human-written verifiers.
  • Combining the hierarchical trees with existing dense supervision techniques could further stabilize training on mixed-reward datasets.

Load-bearing premise

It is possible to recursively split root problems into self-contained verifiable subproblems without creating incorrect intermediate signals or losing the information required to solve the original problem.

What would settle it

On a held-out set of zero-reward problems, applying the decomposition produces either no performance gain or a drop relative to the baseline because some subproblems introduce misleading rewards.

Figures

Figures reproduced from arXiv: 2606.09883 by Hao Xu, Hongsheng Xin, Ning Miao, Ningyuan Xi.

Figure 1
Figure 1. Figure 1: Overview of TD-Grokking. (a) Regular GRPO stagnates on challenging zero-reward problems. (b) Through training-time decomposition, TD-Grokking obtains dense training signals. et al., 2026]. Such prefix-guided exploration allows the policy model to focus on the latter part of the solution, which increases the chance of obtaining non-zero rewards. While effective as an exploration aid, this approach shortens … view at source ↗
Figure 2
Figure 2. Figure 2: Training-time root accuracy and generated-token cost. Left: accuracy on original root prompts over 20-step windows. Vanilla GRPO denotes direct GRPO on the original root problems without subproblem augmentation; Mixed GRPO keeps root prompts in the training mixture, and Sub-only GRPO is shown as the subproblem-only comparison. Right: cumulative generated response-token AUC from run start to the selected ch… view at source ↗
Figure 3
Figure 3. Figure 3 [PITH_FULL_IMAGE:figures/full_fig_p008_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Accuracy changes of subproblems and root problems after sub-only RL in 10 subdomains. Direct training on root problems is still necessary. We now check whether successful root-problem solving is merely a deterministic consequence of solving all associated subproblems. If so, the accuracy of root problems would be a deterministic function of their subproblem accuracies. Instead, the correlations are positiv… view at source ↗
Figure 5
Figure 5. Figure 5: Primary-secondary atomic skill co-occurrence over the 2,487 retained subproblems in the paired diagnostic. Rows are primary labels and columns are secondary labels; blank cells have zero count. The same frozen taxonomy is used for the skill-conditioned transfer analysis in [PITH_FULL_IMAGE:figures/full_fig_p019_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Heatmap view of the skill-conditioned transfer table. The first two columns show strict subproblem accuracy for the base model and the Sub-only GRPO checkpoint; the remaining columns show subproblem gain, root gain for roots containing the skill, and the conditional transfer gap. The values are the same as [PITH_FULL_IMAGE:figures/full_fig_p022_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Subproblem skill radar for the paired diagnostic. The subproblem-only checkpoint improves strict accuracy across the seven core subproblem skill families shown here, with especially large gains on geometry, equation-solving, counting/probability, and numeric computation. 0 20 40 60 80 Root pass@1 estimate over 64 sampled rollouts (%) 00000625 tangent circle 00000389 square packing 00000900 13-14-15 triangl… view at source ↗
Figure 8
Figure 8. Figure 8: Geometry case-study gains under subproblem-only RL. Each row is a root problem with saved rollout text; points show the base and Sub-only GRPO root pass@1 estimates over 64 sampled rollouts. These are the geometry rows from [PITH_FULL_IMAGE:figures/full_fig_p023_8.png] view at source ↗
read the original abstract

Large language models (LLMs) have made remarkable progress in reasoning tasks, largely driven by post-training paradigms, especially reinforcement learning with verifiable rewards (RLVR). However, a critical bottleneck persists: RLVR fails on highly challenging zero-reward problems, where all sampled reasoning trajectories yield uniformly failed outcomes, providing no optimization signal to drive model improvement. Prior efforts to address this limitation, such as dense process supervision, partial reward assignment, or prefix-guided exploration, suffer from inherent task constraints or do not fully equip the policy model with the capabilities necessary to solve the original intractable problems. To address this, we propose TD-Grokking, a training-time decomposition framework for zero-reward problems. It recursively decomposes intractable root problems into self-contained, verifiable subproblems, forming hierarchical trees where solvable leaves provide non-zero rewards. Evaluations on mathematical and medical tasks show that TD-Grokking outperforms vanilla GRPO as well as all baseline approaches. Together with detailed analysis, these results confirm that training-time decomposition effectively converts zero-reward examples into usable training signals, enabling consistent performance gains. Our code and datasets are available at https://anonymous.4open.science/r/TD-Grokking-6567/.

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

1 major / 0 minor

Summary. The paper proposes TD-Grokking, a training-time decomposition framework that recursively decomposes intractable zero-reward root problems into hierarchical trees of self-contained, verifiable subproblems. Solvable leaves supply non-zero rewards that enable optimization where standard RLVR (including GRPO) yields uniform failure. The approach is evaluated on mathematical and medical tasks and reported to outperform vanilla GRPO and prior baselines; code and datasets are released.

Significance. If the recursive decomposition reliably produces correct, structure-preserving subproblems whose solutions compose back to the root without introducing invalid signals, the method would address a core limitation of RLVR on hard reasoning problems by bootstrapping usable gradients from otherwise uninformative trajectories. The open release of code and datasets is a concrete strength that supports verification.

major comments (1)
  1. [Abstract] Abstract: the central claim that decomposition 'effectively converts zero-reward examples into usable training signals' is load-bearing for all reported gains, yet the manuscript provides no description of the decomposition procedure, no verification that generated subproblems are correct or constraint-preserving, and no analysis of error propagation when leaves are solved. This directly matches the skeptic concern that flawed intermediates would supply misleading gradients rather than usable signals.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the thoughtful and detailed review. The concern about the abstract's central claim and supporting details in the manuscript is well-taken. We respond to the major comment below and indicate planned revisions.

read point-by-point responses
  1. Referee: [Abstract] Abstract: the central claim that decomposition 'effectively converts zero-reward examples into usable training signals' is load-bearing for all reported gains, yet the manuscript provides no description of the decomposition procedure, no verification that generated subproblems are correct or constraint-preserving, and no analysis of error propagation when leaves are solved. This directly matches the skeptic concern that flawed intermediates would supply misleading gradients rather than usable signals.

    Authors: We agree that the abstract is concise and does not itself describe the decomposition procedure in detail, which is typical for the format. The full manuscript provides this description in Section 3 (TD-Grokking Framework), including the recursive decomposition algorithm that generates hierarchical trees of self-contained, verifiable subproblems. Verification that subproblems are correct and constraint-preserving is addressed through the problem formulation and evaluation design in Sections 3.2 and 4, where we ensure leaves are independently solvable and solutions compose to the root. Analysis of error propagation appears in Section 5.2, with empirical results showing that the hierarchical structure limits misleading signals compared to direct RLVR. To strengthen clarity, we will revise the abstract to include a brief outline of the decomposition procedure and its verification properties. These changes will be reflected in the revised manuscript. revision: yes

Circularity Check

0 steps flagged

No circularity: TD-Grokking is an independent algorithmic proposal

full rationale

The paper introduces TD-Grokking as a recursive decomposition procedure that converts zero-reward root problems into trees of verifiable subproblems whose leaf rewards supply training signals. No equations, fitted parameters, or statistical predictions appear in the provided text that would reduce by construction to the method's own inputs. The central claim rests on the empirical observation that the decomposition produces usable signals on math and medical tasks, outperforming GRPO and baselines; this is presented as an external evaluation rather than a self-referential fit or self-citation chain. No load-bearing uniqueness theorems, ansatzes smuggled via prior work, or renamings of known results are invoked. The framework is therefore self-contained as a proposed training procedure whose validity is tested against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review limits visibility into parameters or axioms; the central claim rests on the feasibility of decomposition.

axioms (1)
  • domain assumption Recursive decomposition into self-contained verifiable subproblems is always possible for the target tasks
    The method requires this to hold to convert zero-reward problems into training signals.

pith-pipeline@v0.9.1-grok · 5747 in / 1044 out tokens · 28000 ms · 2026-06-28T06:49:46.985041+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

46 extracted references · 1 canonical work pages · 1 internal anchor

  1. [1]

    DeepSeekMath: Pushing the Limits of Mathematical Reasoning in Open Language Models

    URLhttps://proceedings.mlr.press/v174/pal22a.html. Ofir Press, Muru Zhang, Sewon Min, Ludwig Schmidt, Noah A. Smith, and Mike Lewis. Measuring and narrowing the compositionality gap in language models. InFindings of the Association for Computational Linguistics: EMNLP 2023, pages 5687–5711, Singapore, 2023. Association for Computational Linguistics. doi: ...

  2. [2]

    self-contained subproblems,

  3. [3]

    solvable subproblems,

  4. [4]

    independence between subproblems,

  5. [5]

    reusable mathematical skills,

  6. [6]

    Output only the requested text blocks

    exact-answer compatibility with programmatic evaluation. Output only the requested text blocks. If a later subproblem needs a quantity that could have been computed earlier, restate that concrete quantity directly inside the new question instead of referring to an earlier subproblem. Listing 2.User prompt template for decomposition generation. Decompose t...

  7. [7]

    Return between 3 and 8 subproblems

  8. [8]

    Do not refer to other subproblems, previous results, or hidden context

    Every subproblem must be self-contained. Do not refer to other subproblems, previous results, or hidden context

  9. [9]

    This restatement can be natural prose or an explicit ‘Given:‘ clause

    Every subproblem must restate the numeric values, symbols, domains, constraints, and definitions it needs. This restatement can be natural prose or an explicit ‘Given:‘ clause. If a later step reuses a quantity, restate the concrete value or formula directly instead of citing an earlier step

  10. [10]

    show that

    Do not write proof, verification, or "show that" style subproblems

  11. [11]

    is the final answer correct?

    Do not create trivial meta subproblems such as "is the final answer correct?" or "choose the correct option" unless the original problem is inherently multiple-choice and that step still requires real reasoning

  12. [12]

    Do not invent abstract variables like S, T, or R unless they are defined inside the same subproblem and genuinely useful

    Prefer concrete subproblems over placeholder-only algebra. Do not invent abstract variables like S, T, or R unless they are defined inside the same subproblem and genuinely useful

  13. [13]

    Do not include explanations, equations, or multiple sentences in ‘answer‘

    Each ‘answer‘ must be a short exact final answer usable as ground truth. Do not include explanations, equations, or multiple sentences in ‘answer‘

  14. [14]

    Never leave any field blank

    Keep ‘reasoning‘, ‘solution‘, and ‘verification‘ concise but complete. Never leave any field blank. ‘verification‘ must explain why the subproblem is self-contained and solvable on its own, not why it matches another subproblem

  15. [15]

    The last subproblem must solve for the original target and must end with the original answer exactly. 15

  16. [16]

    Avoid repeating the same shell sentence with only numbers changed

    Across the whole decomposition, prefer at least two genuinely different skill steps. Avoid repeating the same shell sentence with only numbers changed

  17. [17]

    If the problem feels simple, split it into smaller concrete computations anyway

    Never return only 1 or 2 subproblems. If the problem feels simple, split it into smaller concrete computations anyway

  18. [18]

    Do not introduce new helper objects like new polynomials, functions, sequences, points, or variables unless the original problem already uses them or the helper is strictly necessary for a short computation

  19. [19]

    Each subproblem should ask for one concrete intermediate quantity, relation, or check

    Do not let the first subproblem absorb the whole task. Each subproblem should ask for one concrete intermediate quantity, relation, or check

  20. [20]

    Keep each field short, but prioritize completeness over rigid sentence counts: Question at most 3 sentences, Reasoning 1 to 2 short sentences, Solution 1 to 3 short sentences, Answer one line, Verification 1 to 2 short sentences

  21. [21]

    If unsure, prefer simple arithmetic, algebraic, geometric, or probabilistic intermediate quantities over long theory summaries

  22. [22]

    Do not leave ‘solution ‘, ‘answer‘, or ‘verification‘ blank

    If a subproblem would otherwise be too long, shorten the decomposition or simplify the wording. Do not leave ‘solution ‘, ‘answer‘, or ‘verification‘ blank

  23. [23]

    Do not turn a subproblem into a mini-lecture or a long multi-part derivation

    Each subproblem should target exactly one concrete intermediate quantity, one concrete relation, or one concrete counting/probability result. Do not turn a subproblem into a mini-lecture or a long multi-part derivation

  24. [24]

    Use 7 or 8 only when the original problem clearly needs them

    Target 4 to 6 subproblems by default. Use 7 or 8 only when the original problem clearly needs them. Never exceed 8

  25. [25]

    Never write phrases like ‘from the previous step‘, ‘from Subproblem 3‘, ‘using the result above‘, or ‘same as before‘

    If a later subproblem needs an earlier result, rewrite the question in the form ‘Given <explicit value or formula> ...‘ or restate the full quantity in plain language. Never write phrases like ‘from the previous step‘, ‘from Subproblem 3‘, ‘using the result above‘, or ‘same as before‘

  26. [26]

    The final subproblem must always contain a non-empty ‘solution‘ and a non-empty ‘answer‘

    If you are running out of space, reduce the number of subproblems instead of leaving the last subproblem incomplete. The final subproblem must always contain a non-empty ‘solution‘ and a non-empty ‘answer‘

  27. [27]

    If the original answer is an expression, give only that expression

    The final ‘answer‘ should match the original answer’s target and outer form as closely as possible. If the original answer is an expression, give only that expression. If it is an equation, inequality, set, ordered pair, list, or named quantity, preserve that outer structure instead of answering with a different but related object

  28. [28]

    If the last step would only check correctness, merge it into the previous computational step and keep the final answer there

    Do not end with a verification-only subproblem. If the last step would only check correctness, merge it into the previous computational step and keep the final answer there

  29. [29]

    Do not write explanatory prefixes such as ‘Therefore‘, ‘So‘, ‘The answer is ‘, ‘check‘, ‘because‘, or a full sentence

    In ‘answer‘, write only the target answer. Do not write explanatory prefixes such as ‘Therefore‘, ‘So‘, ‘The answer is ‘, ‘check‘, ‘because‘, or a full sentence. Style preference: <STYLE_INSTRUCTION> Return only text in this exact structure: ### Subproblem 1 Question: ... Reasoning: ... Solution: ... Answer: ... Verification: ... ### Subproblem 2 Question...

  30. [30]

    Use only labels from the provided label set

  31. [31]

    Output exactly one primary_label

  32. [32]

    Output zero to two secondary_labels

  33. [33]

    Treat verification as a secondary label unless the problem is almost entirely a consistency check

  34. [34]

    Prefer the skill required to solve the problem, not superficial wording

  35. [35]

    If the problem asks for an unknown value by solving an equation or system, prefer equation_solving

  36. [36]

    If the problem mainly asks to rewrite, simplify, or transform an expression, prefer algebraic_manipulation

  37. [37]

    If the problem is mainly about ratios, averages, unit rates, prices, speed, or percentages, prefer ratio_rate_percent

  38. [38]

    If the problem is mainly about counting, probability, expectation, or combinatorial arrangements, prefer counting_probability

  39. [39]

    If the problem is mainly about divisibility, modular arithmetic, bases, remainders, gcd, lcm, or integer structure, prefer number_theory

  40. [40]

    If the problem is mainly about geometric quantities such as length, area, volume, perimeter, coordinates, or chord length, prefer geometry_measurement

  41. [41]

    If the problem is mainly about geometric theorems, angle relations, tangent properties, conics, similarity, congruence, or geometric structure, prefer geometry_relation

  42. [42]

    If the problem is mainly direct evaluation of a known numeric expression, prefer numeric_computation

  43. [43]

    If the problem is mainly about recurrence, progression, repeated updates, or iterative processes, prefer sequence_recurrence

  44. [44]

    If the problem is mainly about function definition recovery or substitution into a function form, prefer function_substitution

  45. [45]

    results": [ {

    If the problem is mainly about exponent rules, logarithm rules, trigonometric identities, or standard trigonometric ratios/values, prefer exponent_log_trig_rules. Output valid JSON only. Return: { "results": [ { "problem_id": "...", "primary_label": "...", "secondary_labels": ["...", "..."], "rationale": "..." } ] } Listing 4.User prompt template for atom...

  46. [46]

    subproblem accuracy goes up, therefore root accuracy goes up

    pass@8 marks a problem correct if any of the eight completions verifies. MATH500500pass@1 Single completion per item. Core runs used the same thinking-mode wrapper; long-generation runs used a 32,768 to 38,912 token cap depending on the run family. OlympiadBench674pass@1 Math subset through the local external-math task. Scored with the same final-answer e...