AI 中文总结
本研究测量四种压缩格式的随机访问块粒度开销，发现成本低至1.6%，并证明LZ77解析的重复距离链可前缀扫描，支持自由分割、追加和GPU解码。
AI 中文摘要
对压缩数据的随机访问通常以密度为代价。我们测量了这一交换比率。在公共语料库上，跨四种格式和九个轴，将254 MB的档案切割成独立可寻址的16 KiB单元的成本，对于绝对偏移格式为档案的1.632%，而对于可寻址zstd则为6.57%，且随着单元缩小，差距扩大：在4 KiB时，分别为5.33%和10.06%。由于成本很小，一些通常不可用的属性随之而来：分割档案是免费的，有时甚至有利可图（在平铺输入上为-0.28%），追加无需更改格式，寻道延迟不依赖于位置，并且一个档案可同时被CPU和GPU解码器读取。我们给出了三个带证明和逐位验证的结构性结果——LZ77解析的重复距离链构成一个替换幺半群，因此无需接触比特流即可前缀扫描；自重叠匹配是周期性的而非链式的；依赖深度允许编码器强制界限——并报告了每个测量的限制及其设置机制。列出了十七个被拒绝的方向及其编号，其中一个将密度提高了26%但被否决。每个声明都带有级别：可通过命令复现、有明确原因的测量或估计。测量工具已单独发布（DOI https://doi.org/10.5281/zenodo.22713364），包含435条有来源的记录。
英文摘要
Random access into compressed data is normally bought with density. We measure the exchange rate. Across four formats and nine axes on a common corpus, the cost of cutting a 254 MB archive into independently addressable 16 KiB units is 1.632% of the archive for an absolute-offset format against 6.57% for seekable zstd, and the gap widens as the unit shrinks: at 4 KiB, 5.33% against 10.06%. Because the cost is small, several properties follow that are usually unavailable: splitting an archive is free and occasionally profitable (-0.28% on tiled input), append needs no format change, seek latency does not depend on position, and one archive is read by both a CPU and a GPU decoder. We give three structural results with proofs and bit-perfect verification - that the repeat-distance chain of an LZ77 parse forms a substitution monoid and is therefore prefix-scannable without touching the bitstream, that self-overlapping matches are periodic rather than chained, and that dependency depth admits an encoder-enforced bound - and we report each measured limit together with the mechanism that sets it. Seventeen rejected directions are listed with their numbers, including one that improved density by 26% and was declined. Every claim carries a level: reproducible by command, measured with a stated reason, or estimated. The measurement tool is released separately (DOI 10.5281/zenodo.22713364) with 435 provenanced records.
Comments7 pages, 5 figures, 6 tables. Sixth paper in the ACEAPEX series (see arXiv:2606.04268, 2606.18900, 2606.24531, 2607.18541, 2608.10188). Code: DOI 10.5281/zenodo.22758786. Measurement tool and 435 records: DOI 10.5281/zenodo.22713364
