Most data that is inherently discrete needs to be compressed in such a way that it can be recovered exactly, without any loss. Examples include text of all kinds, experimental results, and statistical databases. Other forms of data may need to be stored exactly, such as images---particularly bilevel ones, or ones arising in medical and remotesensing applications, or ones that may be required to be certified true for legal reasons. Moreover, during the process of lossy compression, many occasions for lossless compression of coefficients or other information arise. This paper surveys techniques for lossless compression. The process of compression can be broken down into modeling and coding. We provide an extensive discussion of coding techniques, and then introduce methods of modeling that are appropriate for text and images. Standard methods used in popular utilities (in the case of text) and international standards (in the case of images) are described. Keywords Text compression, ima...

Suppose that $S$ is a string of length $m$ drawn from an alphabet of $n$ characters, $d$ of which occur in $S$. Let $P$ be the relative frequency distribution of characters in $S$. We present a new algorithm for dynamic coding that uses at most \(\lceil \lg n \rceil 1\) bits to encode each character in $S$

The paper discusses the main aspects of a parallel debugger for the parallel object-oriented language pSather. PSather provides for a single shared-address space and for multiple threads per processor. Threads can arbitrarily migrate between processors. The debugger supports cyclic debugging which is a standard and quite effective technique for sequential programs. To address nondeterminism, deterministic replay is provided. For that reason, one program run is traced. The debugger uses these traces to repeatedly and identically reexecute the recorded program run. An efficient trace and replay scheme that is in particular suited for pSather and that reduces program perturbation and trace file length is presented. Furthermore, breakpoints and single-stepping for such a debugger using deterministic replay are discussed. 1 Introduction Debugging of sequential programs seems to be well understood. The standard technique is testing until an error manifests as a program failure and then to l...

In view of a booming market for microelectronic implants, our ongoing research work is focusing on the specification and design of a novel biomedical microprocessor core targeting a large subset of existing and future biomedical applications. Towards this end, we have taken steps in identifying various tasks commonly required by such applications and profiling their behavior and requirements. A prominent family of such tasks is lossless data compression. In this work we profile a large collection of compression algorithms on suitably selected biomedical workloads. Compression ratio, average and peak power consumption, total energy budget, compression rate and program-code size metrics have been evaluated. Findings indicate the best-performing algorithms across most metrics to be mlzo (scores high in 5 out of 6 imposed metrics) and fin (present in 4 out of 6 metrics). Further mlzo profiling reveals the dominance of i) addressgeneration, load, branch and compare instructions, and ii) interdependent logical-logical and logical-compare instructions combinations.

In this paper, we demonstrate that we can effectively use results from the field of adaptive self-organizing data structures in enhancing compression schemes. Unlike adaptive lists, which have already been used in compression, to the best of our knowledge, adaptive self-organizing trees have not been used in this regard. To achieve this, we introduce a new data structure, the Partitioning Binary Search Tree (PBST) which, although based on the well-known Binary Search Tree (BST), also appropriately partitions the data elements into mutually exclusive sets. When used in conjunction with Fano encoding, the PBST leads to the so-called Fano Binary Search Tree (FBST), which, indeed, incorporates the required Fano coding (nearly-equal-probability) property into the BST. We demonstrate how both the PBST and FBST can be maintained adaptively and in a self-organizing manner. The updating procedure that converts a PBST into an FBST, and the corresponding new tree-based operators, namely the Shift-To-Left (STL) and the Shift-To-Right (STR) operators, are explicitly presented. The encoding and decoding procedures that also update the FBST have been implemented and rigorously tested. Our empirical results on files of the well-known benchmark, the Canterbury corpus, show that the adaptive Fano coding using FBSTs, the Huffman, and the greedy adaptive Fano coding achieve similar compression ratios. However, in terms of encoding/decoding speed, the new scheme is much faster than the latter two in the encoding phase, and they achieve approximately the same speed in the decoding phase. We believe that the same philosophy, namely that of using an adaptive self-organizing BST to maintain the frequencies, can also be utilized for other data encoding mechanisms, even as the Fenwick scheme has been used in arithmetic coding. 1

Despite the fact that computer memory costs havedecreased dramatically over the past few years, data storage still remains, and will probably always remain, an important cost factor for many large scale database applications. Compressing data in a database system is attractive for two reasons: data storage reduction and performance improvement. Storage reduction is a direct and obvious benefit, while performance improves because smaller amounts of physical data need to be moved for any particular operation on the database. We address several aspects of reversible data compression and compression techniques: 2 general concepts of data compression; 2 a number of compression techniques; 2 a comparison of the effects of compression on common data types; 2 advantages and disadvantages of compressing data; and 2 future research needs.

Abstract.Cellular Automata (CAs) have been applied successfully to several physical systems, processes and scientific problems that involve local interactions, such as image processing, data encryption and byte error correcting codes. In this paper, we analyze the cellular automata, and we propose a reconfigurable cryptosystem based on 2-D Von Neumann cellular automata as an image protection technique. In our scheme we used 2-D cellular automata to generate a high quality of random number as key stream. The security analysis of our proposed cryptosystem by statistical approach shows the high quality of the encrypted image. A comparative result shows that the performances of our proposed system are superior in encryption time to those of MIE, the VC, and the N/KC. In order to have a fair and detailed evolution, we implemented an AES (Advanced Encryption Standard) processor. The proposed CA reconfigurable processor is compared to the AES. Performance metrics such as the throughput (Mbps), the area (slices), the power consumption, and the correlation results from these implementations (CA and AES processor) are computed and analyzed.

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