Prediction by Partial Matching (PPM) is a lossless compression algorithm which consistently performs well on text compression benchmarks. This paper introduces a new PPM implementation called PPM-Ens which uses unbounded context lengths and ensemble voting to combine multiple contexts. The algorithm is evaluated on the Calgary corpus. The results indicate that combining multiple contexts leads ...

Abstract— Chip Multiprocessors (CMPs) combine multiple cores on a single die, typically with private level-one caches and a shared level-two cache. The gap between processor and memory speed is alleviated primarily by using caches. However, the increasing number of cores on a single chip increases the demand on a critical resource: the shared L2 cache capacity. In this dissertation work , a los...

The effect of squeeze casting process parameters on wear behavior of AC2A aluminium alloy was primarily investigated in this experimental study. Five process parameters, namely squeeze pressure, pouring temperature, die temperature, die material and compression time, each at four levels were chosen and sixteen experimental runs based on L16 orthogonal array were performed. From analysis of vari...

In this work, we present a scheme for the lossy compression of image sequences, based on the Adaptive Vector Quantization (AVQ) algorithm. The AVQ algorithm is a lossy compression algorithm for grayscale images, which processes the input data in a single-pass, by using the properties of the vector quantization to approximate data. First, we review the key aspects of the AVQ algorithm and, subse...

An image compression algorithm using JPEG-LS and cubic spline interpolation (CSI) is presented in this paper. The CSI is developed in order to subsample image data with minimal distortion and to achieve image compression. It has been shown in literatures that the CSI can be combined with the transform-based image compression algorithm to develop a modified image compression codec. The compressi...

This paper presents conditional versions of Lempel-Ziv (LZ) algorithm for settings where compressor and decompressor have access to the same side information. We propose a fixed-length-parsing LZ algorithm with side information, motivated by the Willems algorithm, and prove the optimality for any stationary processes. In addition, we suggest strategies to improve the algorithm which lower the d...

In 1994 Burrows and Wheeler [3] described a universal data compression algorithm (BWalgorithm, for short) which achieved compression rates that were close to the best known compression rates. Due to it’s simplicity, the algorithm can be implemented with relatively low complexity. Fenwick [5] described ideas to improve the efficiency (i.e. the compression rate) and complexity of the BW-algorithm...

Effective document compression algorithms require that scanned document images be first segmented into regions such as text, pictures, and background. In this paper, we present a multilayer compression algorithm for document images. This compression algorithm first segments a scanned document image into different classes, then compresses each class using an algorithm specifically designed for t...

Classification and compression are common operations in image processing. Conventionally, compression and classification algorithms are independent of each other and performed sequentially. In this paper, a new algorithm is developed, where the two operations are combined in order to optimize some given classification metrics. In other words, the compression ratio is maximized under classificat...

In this paper we fix our attention on the second step algorithms of the Burrows–Wheeler compression algorithm, which in the original version is the Move To Front transform. We discuss many of its replacements presented so far, and compare compression results obtained using them. Then we propose a new algorithm that yields a better compression ratio than the previous ones.