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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 the content 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 Evaluation of Economy in a Zero-sum Perfect Information Game -
A zero-sum perfect information game is one where every player knows all the moves. Chess is a good example where the object is to checkmate or capture the enemy king. One important feature of checkmates, especially in chess problem composition, is economy. This paper proposes a computational function to evaluate the economy of checkmate configurations on the chessboard. Several experiments were performed comparing chess compositions and regular games to validate the function. The results suggest that the proposed evaluation function is able to correctly discern economical differences in checkmate positions to a high degree of statistical significance and correlates positively with the perception of human chess players. This evaluation function can therefore be useful in increasing the versatility of chess database search engines, as a component in aesthetic models of chess and aiding judges in chess composition tournaments.
... Selectively Convertible Authenticated Encryption in the Random Oracle Model -
Conventionally, a verified digital signature releases information about both the signing event and the signed content simultaneously, where the signing event proves the truth that someone actually signed something. However, in many cases, the information of the signing event and the signed content have different uses and distinct degrees of importance on various occasions. In such cases, the conventional digital signature, the current authenticated encryption schemes and the current signcryption schemes cannot satisfy the needs of selectively releasing either the information about the signing event or that about the signed content or both depending on the situation. In this paper, we shall propose a selectively convertible authenticated encryption scheme where either the sender or the designated receiver can selectively convert the encryption such that the signing event and that of the signed content can be released adaptively... Modeling ODP Computational Specifications Using UML -
The open distributed processing (ODP) computational viewpoint describes the functionality of a system and its environment in terms of a configuration of objects interacting at interfaces, independently of their distribution. Quality of service (QoS) contracts and service level agreements are an integral part of any computational specification, which are specified in ODP in terms of environment contracts. Up until unified modeling language (UML) version 2, both the lack of precision in the UML definition and the semantic gap between the ODP concepts and the UML constructs hindered its application for ODP computational viewpoint modeling. With the advent of UML 2 the situation has changed, because its semantics have been more precisely defined and it now incorporates a whole new set of concepts more apt for modeling the structure and behavior of distributed systems. In this paper, we explore the benefits provided by the new extension mechanisms of UML for modeling the ODP computation... Analysis of Linear Time Sorting Algorithms -
We derive CPU time formulae for the two simplest linear time-sorting algorithms, linear probing sort and bucket sort, as a function of the load factor, and show agreement with experimentally measured CPU times. This allows us to compute optimal load factors for each algorithm, whose values have previously been identified only approximately in the literature. We also present a simple model of cache latency and apply it not only to linear probing sort and bucket sort, where the bulk of the latency is due to random access, but also to the log–linear algorithm quicksort, where the access is primarily sequential, and again show agreement with experimental CPU times. With minor modifications, our model also fits CPU times previously reported by LaMarca and Ladner for radix sort, and by Rahman and Raman for most significant digit radix sort, Flashsort1, and memory tuned quicksort.
... Efficient Algorithms for Integer Division by Constants Using Multiplication -
We present a complete analysis of the integer division of a single unsigned dividend word by a single unsigned divisor word based on double-word multiplication of the dividend by an inverse of the divisor. The well-known advantage of this method yields run-time efficiency, if the inverse of the divisor can be calculated at compile time, since multiplication is much faster than division in arithmetic units. Our analysis leads to the discovery of a limit to the straightforward application of this method in the form of a critical dividend, which fortunately associates with a minority of the possible divisors (20%) and defines only a small upper part of the available dividend space. We present two algorithms for ascertaining whether a critical dividend exists and, if so, its value along with a circumvention of this limit. For completeness, we include an algorithm for integer division of a unsigned double-word dividend by an unsigned single-word divisor in which the quotient is not limi... Composition of Self-Adapting Components for Customizable Systems -
Software systems grow each day in size and complexity. In an effort to manage increasing complexity and to maximize the reuse of code, the software engineering community has, in recent years, put considerable effort into the design and development of component-based software methodologies and tools. Inspired by the notion of connector (Allen and Garlan (1994) Formal connectors. Technical report CMU-CS-94-115, Carnegie Mellon University, PA, USA) in software architecture and the ‘Design by Contract’ metaphor proposed by Meyer ((2000) Object-Oriented Software Construction. Prentice Hall, USA), this paper presents a methodology for component composition, coordination and dynamic adaptation. Our proposal is based on connectors enriched with contracts, making software architecture more explicit at the implementation level. Those connectors will be components in our system. Therefore, we can use subtyping techniques for connectors development and we could offer a set of gener... The Effect of the Distributed Test Architecture on the Power of Testing -
There has been much interest in testing from finite-state machines (FSMs). If the system under test can be modelled by the (minimal) FSM N then testing from an (minimal) FSM M is testing to check that N is isomorphic to M. In the distributed test architecture, there are multiple interfaces/ports and there is a tester at each port. This can introduce controllability/synchronization and observability problems. This paper shows that the restriction to test sequences that do not cause controllability problems and the inability to observe the global behaviour in the distributed test architecture, and thus relying only on the local behaviour at remote testers, introduces fundamental limitations into testing. There exist minimal FSMs that are not equivalent, and so are not isomorphic, and yet cannot be distinguished by testing in this architecture without introducing controllability problems. Similarly, an FSM may have non-equivalent states that cannot be disti... Computing with Time: From Neural Networks to Sensor Networks -
This article advocates a new computing paradigm, called computing with time, that is capable of efficiently performing a certain class of computation, namely, searching in parallel for the closest value to the given parameter. It shares some features with the idea of computing with action potentials proposed by Hopfield, which originated in the field of artificial neuron networks. The basic idea of computing with time is captured in a novel distributed algorithm based on broadcast communication called the lecture hall algorithm, which can compute the minimum among n positive numbers, each residing on a separate processor, using only O(1) broadcasts. When applied to sensor networks, the lecture hall algorithm leads to an interesting routing protocol having several desirable properties.
... 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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