A Study of Energy and Locality Effects using Space-filling Curves

The cost of energy is becoming an increasingly important driver for the operating cost of HPC systems, adding yet another facet to the challenge of producing efficient code. In this paper, we investigate the energy implications of trading computation for locality using Hilbert and Morton space-filling curves with dense matrix-matrix multiplication. The advantage of these curves is that they exhibit an inherent tiling effect without requiring specific architecture tuning. By accessing the matrices in the order determined by the space-filling curves, we can trade computation for locality. The index computation overhead of the Morton curve is found to be balanced against its locality and energy efficiency, while the overhead of the Hilbert curve outweighs its improvements on our test system.Comment: Proceedings of the 2014 IEEE International Parallel & Distributed Processing Symposium Workshops (IPDPSW

Optical and Digital Technique for Watermark Detection

A digital watermark is a visible, or preferably invisible, identification code that is permanently embedded in some digital data to prove owner authentication and provide protection of that document. In this paper we utilize a watermark generation technique based on the use of chaotic functions and the motivation for using these functions is presented. The technique used for watermark embedding is also described, together with a watermark detection scheme based on an optical Matched Filter correlator. We provide results of optical simulations of the watermark detection scheme and show that correlation-based detection is an excellent method for detecting chaotically-generated watermarks embedded in the Fourier domain using multiplicative embedding.We also show that it is possible to detect chaotically-generated watermarks in images that have been subjected to noise

Optical and Digital Technique for Watermark Detection

A digital watermark is a visible, or preferably invisible, identification code that is permanently embedded in some digital data to prove owner authentication and provide protection of that document. In this paper we utilize a watermark generation technique based on the use of chaotic functions and the motivation for using these functions is presented. The technique used for watermark embedding is also described, together with a watermark detection scheme based on an optical Matched Filter correlator. We provide results of optical simulations of the watermark detection scheme and show that correlation-based detection is an excellent method for detecting chaotically-generated watermarks embedded in the Fourier domain using multiplicative embedding.We also show that it is possible to detect chaotically-generated watermarks in images that have been subjected to noise

Geographic Information Systems: The Developer\u27s Perspective

Geographic information systems, which manage data describing the surface of the earth, are becoming increasingly popular. This research details the current state of the art of geographic data processing in terms of the needs of the geographic information system developer. The research focuses chiefly on the geographic data model--the basic building block of the geographic information system. The two most popular models, tessellation and vector, are studied in detail, as well as a number of hybrid data models. In addition, geographic database management is discussed in terms of geographic data access and query processing. Finally, a pragmatic discussion of geographic information system design is presented covering such topics as distributed database considerations and artificial intelligence considerations

Generation and Detection of Watermarks Derived from Chaotic Functions

A digital watermark is a visible, or preferably invisible, identification code that is permanently embedded in digital media, to prove owner authentication thereby providing a level of document protection. In this paper, we review several approaches for the generation of watermarks using chaotic functions, and in particular, the logistic chaotic function. Using this function, in conjunction with seed management, it is to generate chaotic sequences that may be used to create highpass or lowpass digital watermarks.A slight change in the initial conditions will quickly lead to a significant change in the subsequent states of the system, and thus will generate substantially different watermarks. This technique has been shown to offer an added security advantage over tha more traditionally generated watermarks created from pseudorandom sequences, in that only the function seed needs to be stored. It also has the advantage that , through examination of the theoretical properties of the function, it is possible to choose seeds that lead to robust, lowpass watermarks. We review various detection techniques including correlation and statistical methods, and present an analysis of the impact of noise present in a model optical detector. The logistic function presented in this paper is ill defined for certain seed values and has not been fully investigated for the purpose of watermark generation. We consider the impact of the theoretical properties of the logistic function for several chaos-based watermark generation techniques, in particular, their highpass and low pass properties, which when embedded in digital media, are suitable for correlation and statistical based detection methods

Weighted universal image compression

We describe a general coding strategy leading to a family of universal image compression systems designed to give good performance in applications where the statistics of the source to be compressed are not available at design time or vary over time or space. The basic approach considered uses a two-stage structure in which the single source code of traditional image compression systems is replaced with a family of codes designed to cover a large class of possible sources. To illustrate this approach, we consider the optimal design and use of two-stage codes containing collections of vector quantizers (weighted universal vector quantization), bit allocations for JPEG-style coding (weighted universal bit allocation), and transform codes (weighted universal transform coding). Further, we demonstrate the benefits to be gained from the inclusion of perceptual distortion measures and optimal parsing. The strategy yields two-stage codes that significantly outperform their single-stage predecessors. On a sequence of medical images, weighted universal vector quantization outperforms entropy coded vector quantization by over 9 dB. On the same data sequence, weighted universal bit allocation outperforms a JPEG-style code by over 2.5 dB. On a collection of mixed test and image data, weighted universal transform coding outperforms a single, data-optimized transform code (which gives performance almost identical to that of JPEG) by over 6 dB

The Impact of the theoretical properties of the Logistic Function on the generation of optically detectable watermarks

A digital watermark is a visible, or preferably invisible, identification code that is permanently embedded in digital media, to prove owner authentication and provide protection for security or defence documents.In this paper, we present an approach for the generation of watermarks using a logistic chaotic function. Using this function in conjunction with seed management, it is possible to generate chaotic sequences that may be used to create highpass or lowpass digital watermarks. A slight change in the initial conditions will quickly lead to a significant change in the subsequent states of the system, and thus will generate substantially different watermarks. This technique has been shown to offer an added security advantage over the more traditionally generated watermarks created from pseudorandom sequences, in that only the function seed needs to be stored. We have previously presented a study where an optical correlator was suitable for the detection of chaotically generated watermarks.We have also studied the impact of shot noise present in an optical detector for watermarks generated using the logistic function. The logistic function presented in this paper is ill-defined for certained seed values and has not been fully investigated for the purpose of watermark generation. We consider the impact of the theoretical properties of the logistic function on watermark generation and their highpass and lowpass properties, which when embedded in digital media, are suitable for optical detection

A Comparative Study of Chaotic and White Noise Signals in Digital Watermarking

Digital Watermarking is an ever increasing and important discipline, especially in the modern electronically-driven world. Watermarking aims to embed a piece of information into digital documents which their owner can use to prove that the document is theirs, at a later stage. In this paper, performance analysis of watermarking schemes is performed on white noise sequences and chaotic sequences for the purpose of watermark generation. Pseudorandom sequences are compared with chaotic sequences generated from chaotic skew tent map. In particular, analysis is performed on highpass signals generated from both these watermark generation schemes, along with analysis on lowpass watermarks and white noise watermarks. This analysis focuses on the watermarked images after they have been subjected to common image distortion attacks. It is shown that signals generated from highpass chaotic signals have superior performance than highpass noise signals, in the presence of such attacks. It is also shown that watermarks generated from lowpass chaotic signals have superior performance over the other signal types analysed

Block motion estimation using adaptive partial distortion search

Centre for Multimedia Signal Processing, Department of Electronic and Information EngineeringRefereed conference paper2002-2003 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

An adaptive partial distortion search for block motion estimation

2002-2003 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe