Minimum-redundancy prefix codes have been a mainstay of research and commercial compression systems since their discovery by David Huffman more than 50 years ago. In this experimental evaluation we compare techniques ...
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Minimum-redundancy prefix codes have been a mainstay of research and commercial compression systems since their discovery by David Huffman more than 50 years ago. In this experimental evaluation we compare techniques for decoding minimum-redundancy codes, and quantify the relative benefits of recently developed restricted codes that are designed to accelerate the decoding process. We find that table-based decoding techniques offer fast operation, provided that the size of the table is kept relatively small, and that approximate coding techniques can offer higher decoding rates than Huffman codes with varying degrees of loss of compression effectiveness. Copyright (c) 2006 John Wiley & Sons, Ltd.
Intrinsic characterizations by means of analogues of regular expressions are given for six families of regular languages related to the prefix codes, namely their reversals and their closure under union, the right and...
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Intrinsic characterizations by means of analogues of regular expressions are given for six families of regular languages related to the prefix codes, namely their reversals and their closure under union, the right and left ideals, and their complements. First, a characterization for the regular prefix codes is obtained, which is then used to characterize the other families. Characterizations by finite automata are also presented.
In this paper,we exhibit a free monoid containing all prefix codes in connection with the sets of i-th powers of primitive words for all i≥*** extends two results given by Shyr and Tsai in 1998 at the same time.
In this paper,we exhibit a free monoid containing all prefix codes in connection with the sets of i-th powers of primitive words for all i≥*** extends two results given by Shyr and Tsai in 1998 at the same time.
Let m(1), m(2),..., m(t) be a fixed set of natural integers given in ascending order. A multi-delimiter code Dm(1),..., m(t) consists of t words of the form 1(mi)0 and all other binary words with suffixes having one o...
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Let m(1), m(2),..., m(t) be a fixed set of natural integers given in ascending order. A multi-delimiter code Dm(1),..., m(t) consists of t words of the form 1(mi)0 and all other binary words with suffixes having one of the forms 01(mi)0 that cannot occur in other places of a word, i = 1,..., t. Completeness, universality, and density characteristics of multi-delimitercodes are proved. Encoding of integers by multi-delimitercodes is considered in detail. For these codes, fast byte aligned decoding algorithms are also discussed. The comparison of compression rate and decoding speed of Fibonacci codes, (s, c)-dense codes and different multi-delimiter codes is presented. By many useful properties, multi-delimiter codes are superior to Fibonacci codes.
Let L be a finite sequence of natural numbers. In Woryna (2017, 2018), we derived some interesting properties for the ratio rho(n,L) = vertical bar PRn (L)vertical bar/vertical bar UDn(L)vertical bar, where UDn(L) den...
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Let L be a finite sequence of natural numbers. In Woryna (2017, 2018), we derived some interesting properties for the ratio rho(n,L) = vertical bar PRn (L)vertical bar/vertical bar UDn(L)vertical bar, where UDn(L) denotes the set of all codes over an n-letter alphabet and with length distribution L, and PRn(L) subset of UDn(L) is the corresponding subset of prefix codes. In the present paper, we study the case when the length distributions are three-element sequences. We show in this case that the ratio rho(n,L) is always greater than alpha(n), where alpha(n) = (n - 2)/n for n > 2 and alpha(2) = 1/6. Moreover, the number alpha(n) is the best possible lower bound for this ratio, as the length distributions of the form L = (1, 1, c) and L = (1, 2, c) assure that the ratios asymptotically approach alpha(n). Namely, if L = (1, 1, c), then rho(n,L) tends to (n- 2)/n with c -> infinity, and, if L = (1, 2, c), then rho(2,L) tends to 1/6 with c -> infinity. (C) 2020 The Author(s). Published by Elsevier B.V.
We explore the borderline between decidability and undecidability of the following question: " Let C be a class of codes. Given a machine M of type X, is it decidable whether the language L( M) lies in C or not?&...
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We explore the borderline between decidability and undecidability of the following question: " Let C be a class of codes. Given a machine M of type X, is it decidable whether the language L( M) lies in C or not?" for codes in general,omega codes, codes of finite and bounded deciphering delay, prefix, suffix and bi(pre)fix codes, and for finite automata equipped with different versions of push- down stores and counters.
We show that a language L is an s-language if and only if the set of the quotients of L (i.e., the set of the states of its minimal deterministic automaton seen as languages) is a subset of a free monoid generated by ...
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We show that a language L is an s-language if and only if the set of the quotients of L (i.e., the set of the states of its minimal deterministic automaton seen as languages) is a subset of a free monoid generated by a finite set of prefix codes. We demonstrate through examples how to use this result for deciding whether a given language is an s-language. (C) 2003 Elsevier B.V. All rights reserved.
A word which is equal to its mirror image is called a palindrome word. Any language consisting of palindrome words is called a palindrome language. In this paper we investigate properties of palindrome words and langu...
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A word which is equal to its mirror image is called a palindrome word. Any language consisting of palindrome words is called a palindrome language. In this paper we investigate properties of palindrome words and languages. We show that there is no dense regular language consisting of palindrome words. A language contains all the mirror images of its elements is called a reverse closed language. Clearly, every palindrome language is reverse closed. We show that whether a given regular or context-free language is reverse closed is decidable. We study certain properties concerning reverse closed finite maximal prefix codes in this paper. Properties of languages that commute with reverse closed languages are investigated too.
We introduce a notion of coded equivalence in one-sided topological Markov shifts. The notion is inspired by coding theory. One-sided topological conjugacy implies coded equivalence. We will show that coded equivalenc...
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We introduce a notion of coded equivalence in one-sided topological Markov shifts. The notion is inspired by coding theory. One-sided topological conjugacy implies coded equivalence. We will show that coded equivalence implies continuous orbit equivalence of one-sided topological Markov shifts. (C) 2020 Elsevier B.V. All rights reserved.
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