Universal lossless compression via multilevel pattern matching

IEEE Transactions on Information Theory, 2003

A grammar transform is a transformation that converts any data sequence to be compressed into a grammar from which the original data sequence can be fully reconstructed. In a grammar-based code, a data sequence is first converted into a grammar by a grammar transform and then losslessly encoded. In this paper, a greedy grammar transform is first presented; this grammar transform constructs sequentially a sequence of irreducible grammars from which the original data sequence can be recovered incrementally. Based on this grammar transform, three universal lossless data compression algorithms, a sequential algorithm, an improved sequential algorithm, and a hierarchical algorithm, are then developed. These algorithms combine the power of arithmetic coding with that of string matching. It is shown that these algorithms are all universal in the sense that they can achieve asymptotically the entropy rate of any stationary, ergodic source. Moreover, it is proved that their worst case redundancies among all individual sequences of length are upper-bounded by log log log , where is a constant.

2009

Given a sequence S of n symbols over some alphabet Σ, we develop a new compression method that is (i) very simple to implement; (ii) provides O(1) time random access to any symbol of the original sequence; (iii) allows efficient pattern matching over the compressed sequence. Our simplest solution uses at most 2h + o(h) bits of space, where h = n(H0(S) + 1), and H0(S) is the zeroth-order empirical entropy of S. We discuss a number of improvements and trade-offs over the basic method. The new method is applied to text compression. We also propose average case optimal string matching algorithms.

2007 IEEE International Symposium on Information Theory, 2007

In this paper we investigate universal data compression with side information at the decoder by leveraging traditional universal data compression algorithms. Specifically, consider a source network with feedback in which a finite alphabet source X = {Xi} ∞ i=0 is to be encoded and transmitted, and another finite alphabet source Y = {Yi} ∞ i=0 available only to the decoder as the side information correlated with X. Assuming that the encoder and decoder share a uniform i.i.d. (independent and identically distributed) random database that is independent of (X, Y), we propose a string matching-based (variable-rate) block coding algorithm with a simple progressive encoder for the feedback source network. Instead of using standard joint typicality decoding, this algorithm derives its decoding rule from the codeword length function of a traditional universal lossless coding algorithm. As a result, neither the encoder nor the decoder assumes any prior knowledge of the joint distribution of (X, Y) or even the achievable rates. It is proven that for any (X, Y) in the class of all stationary, ergodic source-side information pairs with finite alphabet, the average number of bits per letter transmitted from the encoder to the decoder (compression rate) goes arbitrarily close to the conditional entropy rate H(X|Y) of X given Y asymptotically, and the average number of bits per letter transmitted from the decoder to the encoder (feedback rate) goes to 0 asymptotically.

Most modern lossless data compression techniques used to- day, are based in dictionaries. If some string of data being compressed matches a portion previously seen, then such string is included in the dictionary and its reference is included every time it occurs. A possi- ble generalization of this scheme is to consider not only strings made of consecutive symbols, but more general patterns with gaps between its symbols. In this paper we introduce an o-line method based on this generalization. We address the main problems involved in such approach and provide a good approximation to its solution. Categories and Subject Descriptors: E.4 (Coding and Information Theory)-data compaction and compression; I.2.8 (Artificial Intelli- gence):Problem Solving, Control Methods, and Search-heuristic meth- ods. General Terms: Approximation algorithms, heuristics

2016

A new family of perspective variable length self-synchronazable binary codes with multiple pattern delimiters is introduced. Each delimiter consists of a run of consecutive ones surrounded by zero brackets. These codes are complete and universal. A simple bijective correspondence between natural numbers and any multi-delimiter code set is established. A fast byte aligned decoding algorithm is constructed. Comparisons of text compression rate and decoding speed for different multi-delimiter codes, the Fibonacci code Fib3 and (s, c)-dense codes are also presented.

International Series in Operations Research & Management Science, 2000

Hierarchicallossless. data compression is a compression technique that has been shown to effectively compress data in the face of uncertainty concerning a proper probabilistic model for the data. In this technique, one represents a data sequence x using one of three kinds of structures: (1) a tree called a pointer tree, which generates x via a procedure called "subtree copying"; (2) a data flow graph which generates x via a flow of data sequences along its edges; or (3) a context free grammar which generates x via parallel substitutions accomplished with the production rules of the grammar. The data sequence is then compressed indirectly via compression of the structure which represents it. This article is a survey of recent advances in the rapidly growing field of hierarchical lossless data compression. In the article, we illustrate how the three distinct structures for representing a data sequence are equivalent, outline a simple method for designing compact structures for representing a data sequence, and indicate the level of compression performance that can be obtained by compression of the structure representing a data sequence.

Communications of the ACM, 1987

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES

In this study a new semistatic data compression model that has a fast coding process and that allows compressed pattern matching is introduced. The name of the proposed model is chosen as tagged word-based compression algorithm (TWBCA) since it has a word-based coding and word-based compressed matching algorithm. The model has two phases. In the first phase a dictionary is constructed by adding a phrase, paying attention to word boundaries, and in the second phase compression is done by using codewords of phrases in this dictionary. The first byte of the codeword determines whether the word is compressed or not. By paying attention to this rule, the CPM process can be conducted as word based. In addition, the proposed method makes it possible to also search for the group of consecutively compressed words. Any of the previous pattern matching algorithms can be chosen to use in compressed pattern matching as a black box. The duration of the CPM process is always less than the duration of the same process on the texts coded by Gzip tool. While matching longer patterns, compressed pattern matching takes more time on the texts coded by compress and end-tagged dense code (ETDC). However, searching shorter patterns takes less time on texts coded by our approach than the texts compressed with compress. Besides this, the compression ratio of our algorithm has a better performance against ETDC only on a file that has been written in Turkish. The compression performance of TWBCA is stable and does not vary over 6% on different text files.

A data compression scheme that exploits locality of reference, such as occurs when words are used frequently over short intervals and then fall into long periods of disuse, is described. The scheme is based on a simple heuristic for self-organizing sequential search and on variable-length encodings of integers. We prove that it never performs much worse than Huffman coding and can perform substantially better; experiments on real files show that its performance is usually quite close to that of Huffman coding. Our scheme has many implementation advantages: it is simple, allows fast encoding and decod- ing, and requires only one pass over the data to be com- pressed (static Huffman coding takes huo passes).

IEEE Transactions on Information Theory, 2004

It has long been known that the compression redundancy of independent and identically distributed (i.i.d.) strings increases to infinity as the alphabet size grows. It is also apparent that any string can be described by separately conveying its symbols, and its pattern-the order in which the symbols appear. Concentrating on the latter, we show that the patterns of i.i.d. strings over all, including infinite and even unknown, alphabets, can be compressed with diminishing redundancy, both in block and sequentially, and that the compression can be performed in linear time. To establish these results, we show that the number of patterns is the Bell number, that the number of patterns with a given number of symbols is the Stirling number of the second kind, and that the redundancy of patterns can be bounded using results of Hardy and Ramanujan on the number of integer partitions. The results also imply an asymptotically optimal solution for the Good-Turing probability-estimation problem.