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Computers RSS FeedsCapsule Reviews - The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. ...Feed Source: comjnl.oxfordjournals.org Reliability and Performance of Mirrored Disk Organizations -
Disk mirroring or redundant array of independent disk (RAID) level 1 is a popular paradigm to achieve fault-tolerance and a higher disk access bandwidth for read requests. We consider four RAID1 organizations: basic mirroring (BM), group rotate declustering (GRD), interleaved declustering (ID) and chained declustering (CD). The last three organizations provide a more balanced disk load than BM when a single disk fails, but are more susceptible to data loss than BM when additional disks fail. We compare the four organizations from the viewpoint of: (i) reliability [we quote results from [Thomasian, A. and Blaum, M. (2006) Reliability analysis of mirrored disks. IEEE Trans. Comput., 55, 1640–1644.]] (ii) performability, (iii) performance. In (ii) and (iii), we postulate discrete requests to small randomly placed blocks. For (ii), we compute the mean number of disk requests processed to the point where data loss occurs. For the sake of tractability in (iii), the re... A Review of SIMD Multimedia Extensions and their Usage in Scientific and Engineering Applications -
The volume and complexity of data processed by today's personal computers are increasing exponentially, placing incredible demands on the microprocessors. In the meantime, computing performance that can be achieved by increasing the clock speed of a microprocessor is reaching to physical limits thus making the architectural solutions more prominent. Due to this an important architectural feature is added to recent microprocessors, single instruction multiple data (SIMD), which is a set of instructions that can speed up an application performance by allowing basic operation to be performed on multiple data elements in parallel with fewer instructions. The SIMD computational technique was introduced in the IA-32 Intel® architecture with MMX technology and then further enhanced with Intel's introduction of streaming SIMD extensions (SSE), SSE 2 (SSE2) and SSE 3 (SSE3). Although programming using these SIMD extensions enables software to achieve higher performance, sever... Affordance and Symmetry in User Interfaces -
Affordance is a widely used term in human–computer interaction (HCI) that, while familiar and attractive, does not have a clear operational definition. Using the mathematical concept of symmetry, this paper shows that it is possible to begin developing an operational definition for significant aspects of affordance by forming the theoretical concept of symmetry-affordance. The proposed definition restricts symmetry-affordance to particular contexts but in doing so makes it more useful, as it is clear how to exploit symmetry to aid design. The definition is in standard mathematics (in fact, group theory and model theory) and requires little additional structure. In examining symmetry-affordance, it becomes clear that some other HCI notions can be similarly interpreted by symmetry. The paper provides examples and design insights. Symmetry, as wide or as narrow as you may define its meaning, is one idea by which man through the ages has tried to comprehend and create orde... The Collective Index: A Technique for Efficient Processing of Progressive Queries -
The emergence of modern data-intensive applications requires sophisticated database techniques for processing advanced types of user queries on massive data. In this paper, we study such a new type of query, called progressive queries. A progressive query is defined as a set of inter-related and incrementally formulated step-queries. A step-query in a progressive query PQ is specified on the fly based on the results of previously-executed step-queries in PQ. Hence, a progressive query cannot be formulated in advance before its execution, which raises challenges for its processing and optimization. We introduce a query model to characterize different types of progressive queries. We then present a new index structure, called the collective index, to efficiently process progressive queries. The collective index technique incrementally evaluates step-queries via dynamically maintained member indexes. Utilizing the special structure of a collective index, the (member) indexes on the in... The Availability of Complemental k-Coteries -
k-Coterie is a graceful concept to solve the distributed k-mutual exclusion problem. The k-mutual exclusion algorithm adopting k-coteries could provide the fault-tolerant capability. The complementalness and the availability are two important metrics to measure the fault-tolerant capability of a k-coterie. Since those two metrics are defined under two different failure assumptions, for a given k-coterie, two independent works to measure those two metrics are necessary. In this paper, we derive the characteristics of the complemental k-coterie on its availability. With the characteristic, verifying the complementalness of a k-coterie and evaluating its availability could be combined together to reduce the redundant works on measuring the fault-tolerant capability of the k-coterie.
... Vertex-ordering Algorithms for Automatic Differentiation of Computer Codes -
In the context of Automatic Differentiation (AD) of functions represented by computer code via the vertex elimination approach first advocated by Griewank and Reese (On the Calculation of Jacobian Matrices by the Markowitz Rule. In Griewank, A. and Corliss, G.F. (eds), Automatic Differentiation of Algorithms: Theory, Implementation and Application, pp. 126–135. SIAM, 1991, Philadelphia, PA.), we present two approximate algorithms based on the linearized computational graph of the input code. The first is a statement-reordering algorithm aiming to tune the AD-generated code so as to maximize its performance for modern superscalar processors. The second is aimed at detecting interface contractions introduced by Bischof and Haghighat (Hierarchical Approaches to Automatic Differentiation. In Berz, M., Bischof, C., Corliss, G. and Griewank, A. (eds), Computational Differentiation: Techniques, Applications, and Tools, pp. 83–94. SIAM, 1996, Philadelphia, PA) in order t... An Introduction to Reversible Latches -
Reversible logic has been suggested as one solution to the problem of power consumption in today's electronic devices. This paper addresses the issue of designing reversible latches and provides an overview and analysis of some proposed designs.
... Visual Cryptography Schemes with Reversing -
The Visual cryptography scheme (VCS) is a perfect secure method that encrypts a secret image by breaking it into shadow images. A distinctive property of VCS is that one can visually, without computation, decode the secret by superimposing shadow images. However, much of the contrast of the reconstructed image is lost. A different kind of VCS has been recently proposed by Viet and Kurosawa, called VCS with reversing, allowing participants to perform a reversing operation (reverse black and white) on shadow images. Two drawbacks of the Viet–Kurosawa VCS are: (1) one can only reconstruct an almost ideal contrast image but not an ideal contrast image and (2) the Viet–Kurosawa VCS is constructed just from a perfect black VCS. This paper shows a real perfect contrast VCS such that the black and white pixels are perfectly reconstructed within finite runs, no matter what VCS (perfect black or non-perfect black) is used.
... Synchronized Interactions in Spiked Neuronal Networks -
The study of artificial neural networks has originally been inspired by neurophysiology and cognitive science. It has resulted in a rich and diverse methodology and in numerous applications to machine intelligence, computer vision, pattern recognition and other applications. The random neural network (RNN) is a probabilistic model which was inspired by the spiking behaviour of neurons, and which has an elegant mathematical treatment that provides both its steady-state behaviour and offers efficient learning algorithms for recurrent networks. Second-order interactions, where more than one neuron jointly act upon other cells, have been observed in nature; they generalize the binary (excitatory–inhibitory) interaction between pairs of cells and give rise to synchronous firing (SF) by many cells. In this paper, we develop an extension of the RNN to the case of synchronous interactions, which are based on two cells that jointly excite a third cell; this local behaviour is in fact ... The Future of Computer Technology and its Implications for the Computer Industry -
Progress in computer technology over the last four decades has been spectacular, driven by Moore's law which, though initially an observation, has become a self-fulfilling prophecy and a boardroom planning tool. Although Gordon Moore expressed his vision of progress simply in terms of the number of transistors that could be manufactured economically on an integrated circuit, the means of achieving this progress was based principally on shrinking transistor dimensions, and with that came collateral gains in performance, power-efficiency and, last but not least, cost. The semiconductor industry appears to be confident in its ability to continue to shrink transistors, at least for another decade or so, but the game is already changing. We can no longer assume that smaller circuits will go faster, or be more power-efficient. As we approach atomic limits, device variability is beginning to hurt, and design costs are going through the roof. These are impacting the economics of design in ... DNA Profiles Link Dope to Its Source - 09 Jul 03
Forensic scientists in the U.S. are applying DNA fingerprinting methods to the cannabis plant. They say the technique, which is being used to create a database of DNA profiles of different marijuana plants, will help them to trace the source of any sample.
'It links everybody together: the user, the distributor, the grower,' says the database's creator, Heather Miller Coyle of the Connecticut State Forensic Science Laboratory in Meriden. 'That's the real intent of it, to show it's not just one guy with a little bag of marijuana, but it's a group of people.'
A method for spotting the tiniest traces of marijuana, based on detecting DNA unique to cannabis chloroplasts, has already been developed in the UK (New Scientist print edition, 07 Aug 1999). B... Mathematics: Does the Proof Stack Up? - by George Szpiro
03 Jul 03
Just under five years ago, Thomas Hales made a startling claim. In an e-mail he sent to dozens of mathematicians, Hales declared that he had used a series of computers to prove an idea that has evaded certain confirmation for 400 years. The subject of his message was Kepler's conjecture, proposed by the German astronomer Johannes Kepler, which states that the densest arrangement of spheres is one in which they are stacked in a pyramid - much the same way as grocers arrange oranges.
Soon after Hales made his announcement, reports of the breakthrough appeared on the front pages of newspapers around the world. But today, Hales's proof remains in limbo. It has been submitted to the prestigious Annals of Mathematics, but... Scientists Discover Planetary System Similar to Our Own -
The image shows an impression by David A. Hardy of a possible scene from a moon orbiting the extra-solar planet in orbit around the star HD70642. Photo Credit: David A. Hardy.
... Hacker How-To Good Summer Reading - by Michelle Delio
27 Jun 03
Stealing the Network: How to Own the Boxby Ryan RussellSyngress, 330 pp., $49.95
Stealing The Network: How to Own the Box, a compendium of tales written by well-known hackers, is a perfect summer read. The stories are fictional. The technology and techniques described are very real.
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