REVIEW 4 major objections 5 minor 3 cited by
Not All Correct Answers Are Equal: Why Your Distillation Source Matters
T0 review · 4 major / 5 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read Distillation source determines student reasoning quality: training Qwen2.5-32B on AM-Thinking-v1 distilled data beats training on Qwen3-235B-A22B or DeepSeek-R1 distilled data on AIME2024, AIME2025, MATH500, and LiveCodeBench under the…
desk verdict Large parallel distillation comparison with released data, but teacher attribution is confounded by per-teacher filtering. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is a set of three parallel, verified distillation datasets built from a shared corpus of 1.89 million queries, each query answered by all three teachers and accepted only when an automatic verifier gave a score of at least 0.9. Per-category verifiers (math, code, science, instruction following, multi-turn chat, and general reasoning) enforce correctness, while perplexity filtering, n-gram deduplication, and logical checks shape quality. The comparison works because student model, data volume, training hyperparameters, and evaluation protocol are held constant; the only intended difference is which teacher produced the traces. The paper's explanatory mechanism is distributional: AM-Thinking-v1 data has lower perplexity and a wider token-length spread, which the authors link to the student's observed adaptive output lengths.
What would settle it
Run the same three-way comparison again with identical perplexity thresholds, a fixed and reported maximum number of regeneration attempts per query, and matched final dataset sizes; if the AM-Thinking-v1 student no longer beats the others by a wide margin, the teacher-source explanation fails.
Extended reading notes
Core claim
The paper's central claim is that teacher identity, not just answer correctness, determines how much reasoning skill a student model absorbs. Holding the student base model (Qwen2.5-32B), the 1.89M query set, and the training recipe fixed, swapping only the teacher changes final benchmark performance by up to roughly 19 points on AIME2025. The AM-Thinking-v1-distilled student is best on all four benchmarks; its data is characterized by lower mean perplexity (2.5 vs 2.9 and 3.0) and a token-length distribution with both many short traces and many very long traces. The paper interprets these distributional properties as the mechanism: they teach the student to generate longer solutions when the problem demands it and shorter ones when it does not. This frames distillation quality as a property of the reasoning trace as a whole, not merely of the final answer's correctness.
Load-bearing premise
The comparison assumes the three datasets differ only in which teacher produced them; however, each teacher's outputs were cleaned with a different quality cutoff and regenerated until they passed a score threshold, so part of the measured gap could come from how aggressively each dataset was filtered rather than from the teacher itself.
Editorial extensions
If this is right
- Training on AM-Thinking-v1-distilled data gives a Qwen2.5-32B student 84.3 on AIME2024, 72.2 on AIME2025, 98.4 on MATH500, and 65.9 on LiveCodeBench—higher than the Qwen3- and DeepSeek-R1-distilled students on every benchmark.
- A student's response length becomes adaptive when its training data contains both very short and very long verified traces: it generates roughly 18,000 tokens on AIME2025 but only about 3,500 tokens on MATH500.
- Lower perplexity of the training signal tracks lower training loss throughout optimization, so data quality is visible in training dynamics, not only in final scores.
- The released AM-Thinking-v1 and Qwen3-235B-A22B distilled datasets let others reproduce the comparison and test whether the pattern holds for other student sizes and training budgets.
Reading between the lines
- A controlled follow-up that equalizes filtering thresholds and regeneration budgets across teachers would separate the teacher effect from the curation effect; the paper's current numbers cannot distinguish the two.
- If the active ingredient is token-length diversity rather than the identity of the teacher, resampling the Qwen3 or DeepSeek-R1 outputs to match AM-Thinking-v1's length distribution while keeping content fixed would transfer much of the measured benefit.
- The same three parallel verified datasets, trained on smaller and larger student bases, would show whether the teacher ordering is stable across model capacity and whether the adaptive-length benefit grows with scale.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper reports a large-scale parallel distillation study: for a shared corpus of 1.89 million queries, it collects verified reasoning traces from three teacher models (AM-Thinking-v1, Qwen3-235B-A22B, and DeepSeek-R1), constructs three parallel datasets, and trains Qwen2.5-32B students on each. The authors analyze token-length and perplexity distributions, then evaluate the students on AIME2024, AIME2025, MATH500, and LiveCodeBench. The AM-Thinking-v1-distilled model consistently obtains the highest scores (e.g., 84.3 on AIME2024, 72.2 on AIME2025, 98.4 on MATH500, 65.9 on LiveCodeBench), leading to the conclusion that the distillation source materially affects student reasoning quality. The paper also analyzes generation-length behavior and releases two of the three distilled datasets.
Significance. If the comparison were clean, this would be a valuable empirical contribution: it provides large-scale, verified, parallel distillation data from multiple teachers and demonstrates that teacher identity can shape student performance on reasoning benchmarks. The release of the AM-Thinking-v1 and Qwen3-235B-A22B distilled datasets is a useful community resource, and the decontamination and verification pipeline is described with unusual care. However, the central causal claim—that teacher identity rather than data-construction choices drives the performance gaps—is weakened by protocol differences across teachers in filtering and verification effort, and by the absence of statistical uncertainty estimates on the headline benchmark numbers. The data-quality analysis (perplexity) is also partly self-referential because the scorer is a same-team model. The resource and descriptive findings are significant; the causal attribution requires additional controls.
major comments (4)
- [2.2 (Data Distilling), Perplexity-based Filtering] The paper states that perplexity filtering was applied with 'each model employing a different threshold.' This directly undermines the comparability of the three datasets: if AM-Thinking-v1 data were filtered more aggressively, the lower mean PPL in Figure 5 and the higher benchmark scores in Table 1 could result from data selection rather than from teacher output quality. Please report the exact threshold used for each teacher's data, the final dataset sizes after filtering, and ideally a control experiment in which all three datasets are filtered at the same threshold or matched in size and PPL distribution.
- [2.2 (Data Distilling), Distillation Framework] The verification loop repeats generation 'until the generated response satisfied the verification criterion (score ≥ 0.9)' with no reported cap on attempts, no per-teacher pass rate, and no final dataset sizes. If one teacher required substantially more generation attempts or failed verification more often, the resulting training data would reflect selection effort and query-level difficulty in a way that is not held constant across teachers. Please report the sampling budget, verification pass rate, and final instance counts for each teacher, or modify the protocol to use a fixed number of attempts per query.
- [3.2 and Table 1 (Results)] The benchmark differences that support the headline claim are small on the AIME tasks, which contain only 30 questions each: AIME2024 84.3 vs. 79.4 is a difference of 1.5 questions, and AIME2025 72.2 vs. 62.2 is a difference of 3 questions. No confidence intervals, significance tests, or per-question pass rates are reported, so it is unclear whether these gaps are robust to evaluation noise. Please provide confidence intervals (e.g., bootstrap over the 30 questions) or multiple evaluation seeds for all benchmarks, especially AIME2024 and AIME2025.
- [2.3 (Data Analysis), Figure 5] The claim that AM-Thinking-v1 data has 'better overall quality' because of its lower mean PPL is not supported as independent evidence. The PPL scorer is a 32B model from the same team (reference [30]), and the filtering threshold was allowed to differ per teacher. Lower PPL on the filtered dataset could be a direct consequence of a more aggressive PPL cutoff rather than of genuine output quality. Please report the PPL distribution before filtering, use an external or at least independently trained scorer for at least a subset, and avoid presenting PPL as a quality measure without calibration against downstream task performance.
minor comments (5)
- [Figure 2 caption] The caption contains a typo: 'AM-Thinkin-v1' should be 'AM-Thinking-v1'.
- [Section 3.2 (Benchmarks and Evaluation Setup), MATH500] The text says 'Each prompt was answered once, and we sampled 4 times to compute pass@1,' which is internally inconsistent: sampling 4 times and computing pass@1 is not standard; please clarify whether this is pass@1 from a single sample or a top-k or majority-based metric, and use a consistent nomenclature.
- [Section 4, Table 2] The text emphasizes that AM-Thinking-v1 produces longer outputs on AIME and LiveCodeBench and shorter on MATH500, but Table 2 shows that DeepSeek-R1 produces the longest outputs on LiveCodeBench (30731.0 tokens). Please clarify that the adaptivity claim is about the AM model across tasks, not about being the longest per task, and discuss whether length itself or length diversity is the more likely driver.
- [Section 4 (Results and Analysis), loss curves] Lower training loss on different target distributions is not by itself evidence of 'more learnable, coherent, and high-quality' data; it may simply reflect that the AM-Thinking-v1 responses are easier to model by the Qwen2.5-32B base. Please temper this interpretation or provide a control such as loss on a held-out set of same-distribution data.
- [Section 5 (Conclusion)] The manuscript releases only the AM-Thinking-v1 and Qwen3-235B-A22B distilled datasets, not the DeepSeek-R1 data; this limits independent replication of the three-way comparison. Consider releasing the DeepSeek-R1 data as well, or clearly state where users can obtain an equivalent dataset.
Circularity Check
Central benchmark comparison is externally grounded; only the PPL-based quality analysis is partly self-referential.
-
fitted input called prediction
[Section 2.2 (Quality Assurance Measures) and Section 2.3 (Figure 5, PPL distributions)]
"Perplexity-based Filtering: We computed perplexity scores using a strong 32B language model [30], with each model employing a different threshold. Notably, responses distilled from AM-Thinking-v1 demonstrated the lowest perplexity among the three models. ... Among the three datasets, AM-Thinking-v1 achieves the lowest mean PPL (2.5), suggesting that its distilled outputs are generally of higher quality."
The paper presents AM's lower perplexity as evidence of higher data quality, but the data were selected using that same perplexity metric, with thresholds allowed to differ per teacher. Post-filter PPL is a direct function of the chosen threshold: a stricter cutoff for AM-Thinking-v1 would mechanically lower its mean PPL, so the reported ranking is not an independent property of the teacher's outputs. Since the thresholds are not reported, the 'quality advantage' is at least partly an artifact of the filtering rule rather than a measured teacher characteristic, making the data-quality comparison self-referential rather than a prediction from teacher identity.
full rationale
The paper's headline claim is that distillation source matters: students trained on AM-Thinking-v1-distilled data outperform students trained on Qwen3-235B-A22B or DeepSeek-R1 distilled data under a shared training recipe. This claim is supported by evaluations on external benchmarks (AIME2024, AIME2025, MATH500, LiveCodeBench), which are independent of the paper's data construction and teacher selection. The same training recipe, learning rate, sequence length, and system prompt are applied to all three student arms, so the benchmark comparison is not circular. The use of same-team references for the training recipe and for the AM-Thinking-v1 teacher does not by itself make the central result circular, because the comparison is empirically evaluated against outside benchmarks. The one genuinely circular-adjacent element is the perplexity-based data-quality analysis: the same perplexity metric was used to filter the data (with per-teacher thresholds) and then cited as evidence that AM data is higher quality. That finding is not load-bearing for the external-benchmark conclusion, but it is a self-referential step in the paper's data-quality narrative, so the overall circularity score is low rather than zero.
Assumptions & free parameters
free parameters (5)
- verify_score threshold =
0.9
- per-model PPL filtering threshold =
undisclosed, differs per teacher
- max sequence length =
32k tokens
- evaluation sampling budgets =
64/16/4 for AIME/LCB/MATH500
- training recipe =
lr 8e-5, batch 64, 2 epochs, 32k seq len
assumptions (3)
- domain assumption Automatic verification with score >= 0.9 is a valid proxy for correct reasoning traces.
- domain assumption Perplexity from a 32B model measures data quality.
- domain assumption Decontamination removed overlap with evaluation benchmarks.
Cite this review
Pith. "Pith review of Not All Correct Answers Are Equal: Why Your Distillation Source Matters." pith.science (2026). https://pith.science/paper/XCMOLLDW
@misc{pith2026250514464,
author = {Pith},
title = {Pith review of: Not All Correct Answers Are Equal: Why Your Distillation Source Matters},
year = {2026},
howpublished = {\url{https://pith.science/paper/XCMOLLDW}},
note = {Machine review of arXiv:2505.14464}
}
read the original abstract
Distillation has emerged as a practical and effective approach to enhance the reasoning capabilities of open-source language models. In this work, we conduct a large-scale empirical study on reasoning data distillation by collecting verified outputs from three state-of-the-art teacher models-AM-Thinking-v1, Qwen3-235B-A22B, and DeepSeek-R1-on a shared corpus of 1.89 million queries. We construct three parallel datasets and analyze their distributions, revealing that AM-Thinking-v1-distilled data exhibits greater token length diversity and lower perplexity. Student models trained on each dataset are evaluated on reasoning benchmarks including AIME2024, AIME2025, MATH500, and LiveCodeBench. The model distilled from AM-Thinking-v1 consistently achieves the best performance (e.g., 84.3 on AIME2024, 72.2 on AIME2025, 98.4 on MATH500, and 65.9 on LiveCodeBench) and demonstrates adaptive output behavior-producing longer responses for harder tasks and shorter ones for simpler tasks. These findings highlight the value of high-quality, verified reasoning traces. We release the AM-Thinking-v1 and Qwen3-235B-A22B distilled datasets to support future research on open and high-performing reasoning-oriented language models. The datasets are publicly available on Hugging Face\footnote{Datasets are available on Hugging Face: \href{https://huggingface.co/datasets/a-m-team/AM-Thinking-v1-Distilled}{AM-Thinking-v1-Distilled}, \href{https://huggingface.co/datasets/a-m-team/AM-Qwen3-Distilled}{AM-Qwen3-Distilled}.}.
Figures
Figures from the paper (3 more)
Forward citations
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When Perplexity Lies: Generation-Focused Distillation of Hybrid Sequence Models
Perplexity-based scoring systematically understates teacher–student gaps in distilled hybrid LLMs and can reverse design-choice rankings; generation-based evaluation is the more reliable protocol.
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A Comprehensive FP8 Training Recipe for Reasoning-Enhanced Language Models
A hybrid-granularity FP8 training recipe achieves near-lossless accuracy versus BF16 on reasoning benchmarks with up to 22% faster training and 14% lower memory.
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Reviewed August 7, 2026 · model on record in the stance chip above.
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