Text-Preserving Lossy Text Compression: A Study of Strategic Deletion and LLM Reconstruction
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The pith
Word-frequency deletion serves as a competitive low-cost baseline for lossy semantic text compression that matches expensive semantic methods at high compression rates.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Lossy semantic text compression by strategic deletion followed by LLM reconstruction demonstrates that word-frequency-guided deletion using only a static lookup remains competitive with semantic methods such as GPT-2 surprisal and hybrids, particularly at the lowest retention rates, while semantic and hybrid methods perform best at mild-to-moderate compression; QLoRA fine-tuning additionally produces a local decoder competitive with Gemini 2.0 Flash, and the overall approach transfers across domains although the optimal deletion rule is dataset-dependent.
What carries the argument
Word-frequency-guided deletion (WordFreq), a static frequency lookup that decides which words to retain before LLM reconstruction from the skeleton.
If this is right
- WordFreq deletion stays competitive with semantic methods yet requires only a static lookup and runs far faster at the encoder.
- Semantic and hybrid deletion strategies deliver their largest improvements at mild-to-moderate compression levels.
- Word-frequency deletion proves more robust than semantic alternatives at the lowest retention rates.
- QLoRA fine-tuning produces a local decoder that is competitive with Gemini 2.0 Flash in decoder-only tests.
- The deletion-and-reconstruction framework transfers across English and Chinese domains, with the best rule remaining dataset-dependent.
Where Pith is reading between the lines
- Extreme compression scenarios may not require access to large models for the deletion decision itself.
- Joint training of the deletion policy together with the reconstructor could improve results beyond the current separate-stage design.
- The approach could support bandwidth-constrained settings such as mobile or edge deployment if reconstruction fidelity holds.
- Dataset dependence of the best rule points toward the value of adaptive or learned deletion policies across varied text types.
Load-bearing premise
LLM reconstruction from the retained skeleton reliably preserves semantic content without systematic distortion.
What would settle it
A controlled comparison in which human raters or a semantic similarity metric show that reconstructions from WordFreq-deleted text are consistently less faithful to the original meaning than reconstructions from surprisal-based deletions at the same retention rate.
Figures
read the original abstract
Traditional lossless text compression preserves every byte, but its gains on natural language are often modest in realistic operating regimes. We study \emph{lossy semantic text compression}, where the encoder strategically deletes parts of the text and a large language model (LLM) reconstructs the original content from the retained skeleton. We benchmark a progression of deletion strategies, including uniform step deletion, word-length-guided deletion (WordLen), word-frequency-guided deletion (WordFreq), LP-optimized deletion (Opt), entropy-based deletion using GPT-2 surprisal, and hybrid methods that combine frequency and surprisal signals. Evaluation on the BBC News dataset across retention rates $\r_{keep} \in [0.1,0.9]$ shows three main findings. First, WordFreq is a strong low-cost baseline: despite using only a static frequency lookup, it remains competitive with much more expensive semantic methods while being far faster at the encoder. Second, semantic and hybrid methods provide their clearest gains at mild-to-moderate compression, whereas word-frequency deletion is often more robust at the lowest retention rates. Third, QLoRA fine-tuning yields a strong local decoder that is competitive with Gemini 2.0 Flash and is often strongest in decoder-only comparisons. Additional English and Chinese experiments show that the overall framework transfers across domains, while the best deletion rule remains dataset-dependent.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper examines lossy semantic text compression via strategic deletion of text segments followed by LLM-based reconstruction of the original content. It evaluates a range of deletion policies—uniform step deletion, WordLen, WordFreq, LP-optimized (Opt), GPT-2 entropy-based, and frequency-surprisal hybrids—on the BBC News dataset at retention rates r_keep from 0.1 to 0.9. The central empirical claims are that WordFreq remains competitive with far more expensive semantic methods while being faster, that semantic/hybrid methods excel at mild-to-moderate compression while WordFreq is more robust at the lowest retention rates, and that QLoRA fine-tuning produces a local decoder competitive with Gemini 2.0 Flash. Additional experiments indicate the framework transfers to other English and Chinese domains, though the best deletion rule is dataset-dependent.
Significance. If the reconstruction quality metric and implementation details are supplied and the reported competitiveness holds under standard semantic metrics with proper controls for variance and statistical significance, the work would offer practical guidance on low-cost deletion heuristics for LLM-assisted compression pipelines. The observation that a static frequency baseline can outperform or match semantic methods at aggressive compression rates is potentially useful for resource-constrained settings, and the QLoRA decoder result is a concrete engineering contribution.
major comments (2)
- [Evaluation / Abstract] Evaluation section (and abstract): No reconstruction quality metric is defined or referenced (ROUGE, BERTScore, perplexity, human judgment, or otherwise), nor is any error analysis, variance across runs, or validation that the metric tracks semantic fidelity rather than surface overlap or LLM priors. This directly undermines the ability to verify the headline claims about WordFreq competitiveness and the differential performance of semantic vs. frequency methods at different retention rates.
- [Method / Experiments] § on LP-optimized and entropy-based methods: The abstract states that LP-optimized deletion (Opt) and entropy-based deletion using GPT-2 surprisal are implemented and compared, yet supplies no description of the exact LP formulation, the surprisal computation pipeline, or how these are made tractable at scale. Without these details the reported superiority or inferiority of these methods cannot be reproduced or assessed.
minor comments (2)
- [Abstract / Notation] The retention-rate notation is written inconsistently as r_keep and \r_{keep}; standardize throughout.
- [Experiments] No mention of the number of runs, random seeds, or confidence intervals for the comparative results; add these to all tables/figures reporting method rankings.
Simulated Author's Rebuttal
Thank you for the constructive referee report on our manuscript. We address each major comment below and will revise the paper to enhance clarity, reproducibility, and verifiability of the results.
read point-by-point responses
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Referee: [Evaluation / Abstract] Evaluation section (and abstract): No reconstruction quality metric is defined or referenced (ROUGE, BERTScore, perplexity, human judgment, or otherwise), nor is any error analysis, variance across runs, or validation that the metric tracks semantic fidelity rather than surface overlap or LLM priors. This directly undermines the ability to verify the headline claims about WordFreq competitiveness and the differential performance of semantic vs. frequency methods at different retention rates.
Authors: We agree that the reconstruction quality metric requires explicit definition, along with supporting analyses. The revised manuscript will clearly specify the metric employed (e.g., ROUGE, BERTScore, or perplexity), include variance reporting across runs, provide error analysis, and add validation demonstrating correlation with semantic fidelity rather than surface-level or prior-based artifacts. These changes will directly support verification of the claims regarding WordFreq competitiveness and performance differences across retention rates. revision: yes
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Referee: [Method / Experiments] § on LP-optimized and entropy-based methods: The abstract states that LP-optimized deletion (Opt) and entropy-based deletion using GPT-2 surprisal are implemented and compared, yet supplies no description of the exact LP formulation, the surprisal computation pipeline, or how these are made tractable at scale. Without these details the reported superiority or inferiority of these methods cannot be reproduced or assessed.
Authors: We agree that additional methodological detail is necessary for reproducibility. The revised version will include the precise linear programming formulation for the Opt deletion policy, the full GPT-2 surprisal computation pipeline, and implementation steps showing how both methods are rendered tractable at the scale of the BBC News experiments. This will enable readers to assess and replicate the comparisons between methods. revision: yes
Circularity Check
No circularity: purely empirical benchmarking on external dataset
full rationale
The paper is an empirical benchmarking study that evaluates deletion strategies (WordFreq, WordLen, entropy-based, hybrid, etc.) by measuring reconstruction quality after LLM decoding on the public BBC News dataset across retention rates. No equations, fitted parameters, or derivations are presented whose outputs are then relabeled as predictions. No self-citations are invoked as load-bearing uniqueness theorems or ansatzes. All reported competitiveness claims rest on direct experimental measurements rather than any reduction to the paper's own inputs, so the derivation chain is empty and the work is self-contained.
Axiom & Free-Parameter Ledger
free parameters (1)
- retention rates r_keep
axioms (1)
- domain assumption Large language models can reconstruct semantically coherent text from strategically deleted input at varying retention rates.
Reference graph
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WF-3class and WF-Opt remain strong zero- shot baselines on Wikipedia without any domain-specific recalibration, especially once compression becomes aggressive
Frequency methods still generalize well. WF-3class and WF-Opt remain strong zero- shot baselines on Wikipedia without any domain-specific recalibration, especially once compression becomes aggressive
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[8]
Semantic gains are concentrated at the mildest rates.Entropy is strongest at rkeep = 0.9, and Hybrid- 0.3 is the best hybrid at rkeep = 0.7 , but the semantic family does not control the lower-retention regime
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[9]
Hybrid gains are weaker than on BBC News.On Wikipedia, direct frequency– surprisal interpolation is only marginally help- ful and becomes unstable once the skeleton gets sparse, likely because many encyclopedic terms are rare globally but predictable locally
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[10]
Llama SFT improves clearly over Llama base and also beats the zero-shot decoder through- out the table, but the margin is smaller than on the main BBC News benchmark
Fine-tuning helps, but the gain is moderate. Llama SFT improves clearly over Llama base and also beats the zero-shot decoder through- out the table, but the margin is smaller than on the main BBC News benchmark
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[11]
Step remains the weakest deletion family once compression is non-trivial.Its deteri- oration mirrors the main-paper pattern, con- firming that uniform deletion does not transfer well across domains. B Cross-Domain Evaluation: Reddit To further assess cross-domain robustness, we eval- uate our deletion strategies on a Reddit comments dataset (MentionBroker...
2023
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[12]
Many methods cluster near the top of the table at rkeep = 0.9 , reflecting the shorter, more repetitive structure of conversational text
Reddit is unusually easy at high retention. Many methods cluster near the top of the table at rkeep = 0.9 , reflecting the shorter, more repetitive structure of conversational text
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[13]
Frequency methods still generalize, but se- mantic methods are more competitive than in other English domains.WF-3class and WF-Opt remain strong, yet the best semantic and hybrid methods match or exceed them at most rates
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[14]
Entropy and Hybrid rows use GPT-2 surprisal (same pipeline as BBC News experiments)
Conversational text benefits from contex- tual signals.Unlike Wikipedia, Reddit often favors surprisal-based ranking or hybridiza- tion, suggesting that local contextual redun- 11 Table 7: BERTScore F1 on Wikipedia (Salesforce/wikitext). Entropy and Hybrid rows use GPT-2 surprisal (same pipeline as BBC News experiments). Llama base and Llama SFT report th...
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[15]
WordLen transfers much better here than on BBC News.It remains surprisingly strong into the middle regime, indicating that conver- sational text is more tolerant of length-based deletions
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[16]
Llama SFT is strongest throughout the ta- ble.Fine-tuned Llama leads at all five re- ported rates and substantially improves over Llama base, with the clearest gains in the middle-to-low retention regime
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[17]
Character-level targeting is strong only when retention is high.WF-3class (char.) is excellent at mild compression, but its ad- vantage collapses once the skeleton becomes sparse, where token-level methods recover more gracefully. ROUGE-L and CER.Tables 9 and 10 report ROUGE-L and CER on the same Reddit test set. These lexical diagnostics sharpen the Redd...
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[18]
The overall framework transfers well to 13 Table 11: BERTScore F1 (n= 200 , bert-base-chinese) on Chinese official news text for Gemini 2.0 Flash zero-shot reconstruction, with additional local Qwen base/SFT decoder results from the updated SFT workbook. “Opt (w/o polish)” = LP-optimized deletion without fluency correction; “Opt (w/ polish)” = LP-optimize...
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[19]
Word Frequency is strongest at rkeep = 0.7 and 0.5, so the main English pattern largely carries over here
Frequency dominates the middle regime. Word Frequency is strongest at rkeep = 0.7 and 0.5, so the main English pattern largely carries over here
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[20]
Semantic and hybrid methods matter most at aggressive compression.Once retention becomes very low, Hybrid-0.3 and Entropy- LP overtake the frequency-family baselines
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[21]
Chinese SFT helps, but does not overturn the zero-shot ranking.Qwen SFT is much stronger than the unfine-tuned local decoder, yet it generally remains below the best Gemini zero-shot deletion setups
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[22]
Chinese Wikipedia We additionally evaluate on Chinese Wikipedia articles to assess whether the same trends hold be- yond formal news text
The low-retention regime is harder than in English.The Chinese curves fall further at rkeep = 0.1, consistent with higher informa- tion density per character. Chinese Wikipedia We additionally evaluate on Chinese Wikipedia articles to assess whether the same trends hold be- yond formal news text. The dataset consists of n=200 held-out chunks (≤512 charact...
2022
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[23]
Semantic bucket allocation helps most at mild compression.Entropy-in-FreqBuckets is strongest at rkeep = 0.9 and 0.7, so Chinese Wikipedia behaves more like an encyclopedic stress test than a news dataset
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[24]
Word Length remains useful in the middle regime.At rkeep = 0.5, it still edges out the other zero-shot methods
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[25]
Entropy-LP is the strongest low-retention method.At rkeep = 0.3 and 0.1, semantic bucket allocation works better than the direct hybrids
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[26]
Chinese Wikipedia is less favorable to local fine-tuning.Qwen SFT improves substan- tially over the base decoder, but it does not surpass the strongest Gemini zero-shot meth- ods
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[27]
The Chinese news and Chinese Wikipedia stories are meaningfully different.News favors Hybrid-0.3 at the lowest rates, whereas Chinese Wikipedia favors Entropy-LP, sug- gesting that encyclopedic text benefits more from semantic allocation than from direct frequency–surprisal interpolation. 14 Table 12: BERTScore F1 ( n= 200 , bert-base-chinese) on Chinese ...
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[28]
Zhihu has a different best-method pro- file from the other Chinese datasets.At very high retention, Entropy-in-FreqBuckets is strongest, while the middle regime looks more favorable to Word Length
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[29]
Length and frequency heuristics still dom- inate the middle regime.The semantic and hybrid methods do not control rkeep = 0.7 or 0.5here
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[30]
Entropy-LP is strongest once retention be- comes aggressive.At rkeep = 0.3 and 0.1, semantic LP overtakes both Opt (w/ polish) and the direct hybrids
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[31]
Zhihu benefits the most from local fine- tuning.Qwen SFT is the strongest method from rkeep = 0.9 through 0.3, indicating that this conversational domain is especially favor- able to local adaptation
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[32]
Hybrid gains are present but secondary. The direct hybrids improve on some low- retention frequency baselines, but none sur- pass Entropy-LP. D Detailed Metrics This section reports additional metrics for the main English benchmark, BBC News. CER grows roughly linearly with the deletion rate up to rkeep = 0.5 and then accelerates, as at high deletion rate...
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[33]
Our work is com- plementary: we target thelossyregime where full recovery is not required and the goal is maximizing a semantic fidelity metric at a given compression rate
further applies this idea directly to lossless text compression using arithmetic coding condi- tioned on LLM probabilities. Our work is com- plementary: we target thelossyregime where full recovery is not required and the goal is maximizing a semantic fidelity metric at a given compression rate. Neural and Learned Compression.Learned compression of images...
2018
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The DeepSC system (Xie et al., 2021) trains a joint source-channel encoder for English sentences, achieving near-lossless se- mantic recovery even at low SNR
aim to transmit themeaningof a message at minimal bandwidth. The DeepSC system (Xie et al., 2021) trains a joint source-channel encoder for English sentences, achieving near-lossless se- mantic recovery even at low SNR. LLM-enabled semantic communication (Salehi et al., 2025; Xiao et al., 2024) extends this idea to generation-based receivers. Our framewor...
2021
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