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arXiv 2201.05234cs.ITcs.CLmath.ITphysics.data-an
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单文本压缩的最佳字母表

Optimal alphabet for single text compression

Alikhanyan National Laboratory (Yerevan Physics Institute)(阿里哈尼扬国家实验室(埃里温物理研究所));Envoy Media Group(Envoy传媒集团)

Armen E. Allahverdyan, Andranik Khachatryan

摘要:

使用来自给定字母表的符号书写的文本可以使用霍夫曼代码压缩,这最小化了编码文本的长度。然而,有必要采用文本特定的码本,即符号-码字字典来解码原始文本。因此,压缩性能应该通过完整的码长来评估,即编码文本的长度加上码本的长度。我们研究了几种用于压缩文本的字母表--字母、字母的n-gram、音节、单词和短语。如果只保留足够短的文本,则字母表或两克字母是最佳的。对于大多数古腾堡计划文本,最佳字母表(最小化完整代码长度的字母表)由音节或单词给出,这取决于码本的表示。字母3和4-gram的平均长度与音节/单词相当,表现明显不如音节或单词。单词2-grams也从来都不是最好的字母表,因为它有一个非常大的密码本。我们还表明,码本表示是重要的-从一个天真的表示切换到一个紧凑的显着改善了大量的符号,最显着的话,字母表的事项。因此,语言中表达意义的元素(音节或单词)提供了最好的压缩字母表。

英文摘要:

A text written using symbols from a given alphabet can be compressed using the Huffman code, which minimizes the length of the encoded text. It is necessary, however, to employ a text-specific codebook, i.e. the symbol-codeword dictionary, to decode the original text. Thus, the compression performance should be evaluated by the full code length, i.e. the length of the encoded text plus the length of the codebook. We studied several alphabets for compressing texts -- letters, n-grams of letters, syllables, words, and phrases. If only sufficiently short texts are retained, an alphabet of letters or two-grams of letters is optimal. For the majority of Project Gutenberg texts, the best alphabet (the one that minimizes the full code length) is given by syllables or words, depending on the representation of the codebook. Letter 3 and 4-grams, having on average comparable length to syllables/words, perform noticeably worse than syllables or words. Word 2-grams also are never the best alphabet, on the account of having a very large codebook. We also show that the codebook representation is important -- switching from a naive representation to a compact one significantly improves the matters for alphabets with large number of symbols, most notably the words. Thus, meaning-expressing elements of the language (syllables or words) provide the best compression alphabet.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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