TD-Grokking: Learning from Zero-Reward Problems by Training-Time Decomposition
Pith reviewed 2026-06-28 06:49 UTC · model grok-4.3
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.
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
- 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
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.
Referee Report
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)
- [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
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
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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
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
axioms (1)
- domain assumption Recursive decomposition into self-contained verifiable subproblems is always possible for the target tasks
Reference graph
Works this paper leans on
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[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: ...
work page internal anchor Pith review Pith/arXiv arXiv doi:10.18653/v1/2023.acl-long.147 2023
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[2]
self-contained subproblems,
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[3]
solvable subproblems,
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[4]
independence between subproblems,
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[5]
reusable mathematical skills,
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[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...
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[7]
Return between 3 and 8 subproblems
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[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
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[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
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[10]
show that
Do not write proof, verification, or "show that" style subproblems
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[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
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[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
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[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‘
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[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
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[15]
The last subproblem must solve for the original target and must end with the original answer exactly. 15
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[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
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[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
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[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
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[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
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[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
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[21]
If unsure, prefer simple arithmetic, algebraic, geometric, or probabilistic intermediate quantities over long theory summaries
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[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
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[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
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[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
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[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‘
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[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‘
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[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
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[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
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[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...
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[30]
Use only labels from the provided label set
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[31]
Output exactly one primary_label
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[32]
Output zero to two secondary_labels
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[33]
Treat verification as a secondary label unless the problem is almost entirely a consistency check
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[34]
Prefer the skill required to solve the problem, not superficial wording
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[35]
If the problem asks for an unknown value by solving an equation or system, prefer equation_solving
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[36]
If the problem mainly asks to rewrite, simplify, or transform an expression, prefer algebraic_manipulation
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[37]
If the problem is mainly about ratios, averages, unit rates, prices, speed, or percentages, prefer ratio_rate_percent
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[38]
If the problem is mainly about counting, probability, expectation, or combinatorial arrangements, prefer counting_probability
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[39]
If the problem is mainly about divisibility, modular arithmetic, bases, remainders, gcd, lcm, or integer structure, prefer number_theory
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[40]
If the problem is mainly about geometric quantities such as length, area, volume, perimeter, coordinates, or chord length, prefer geometry_measurement
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[41]
If the problem is mainly about geometric theorems, angle relations, tangent properties, conics, similarity, congruence, or geometric structure, prefer geometry_relation
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[42]
If the problem is mainly direct evaluation of a known numeric expression, prefer numeric_computation
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[43]
If the problem is mainly about recurrence, progression, repeated updates, or iterative processes, prefer sequence_recurrence
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[44]
If the problem is mainly about function definition recovery or substitution into a function form, prefer function_substitution
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[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...
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[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...
discussion (0)
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