SUMMARY Adt is a simple tool in the spirit of Lex and Yacc that makes monomorphic algebraic data types, polymorphic built‐in types like the list and an efficient form of pattern matching available in C programs. C programs built with ADTs typically use NULL pointers only to indicate don't care values, and not as sentinels. This reduces the scope for errors involving NULL pointers. The Adt tool generates runtime checks, which catch many of the remaining NULL pointer dereferences. The runtime checks may consume a significant amount of CPU time; hence they can be switched off once the program is suitably debugged. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper we study the use of GSM signal strength information as a method of inferring position. Location fingerprinting using 802.11 wireless networks is a popular positioning technique. Recently, research has been published that has applied this technique to cellular networks. Cellular networks offer wider coverage than 802.11 and enable context-aware applications to be built upon the already ubiquitous cell-phone platform. We focus on the practical aspects of deploying and managing location based services in dynamic, outdoor environments. We have extended a technique for creating a qualitative location system. This extension allows a symbolic location system to be learnt from training data in an unsupervised manner

In this paper we study, through a concrete case, the feasibility of using a high-level, general-purpose logic language in the design and implementation of applications targeting wearable computers. The case study is a "sound spatializer" which, given real-time signals for monaural audio and heading, generates stereo sound which appears to come from a position in space. The use of advanced compile-time transformations and optimizations made it possible to execute code written in a clear style without efficiency or architectural concerns on the target device, while meeting strict existing time and memory constraints. The final executable compares favorably with a similar implementation written in C. We believe that this case is representative of a wider class of common pervasive computing applications, and that the techniques we show here can be put to good use in a range of scenarios. This points to the possibility of applying high-level languages, with their associated exibility, conciseness, ability to be automatically parallelized, sophisticated compile-time tools for analysis and verification, etc., to the embedded systems eld without paying an unnecessary performance penalty.

Ubiquitous and mobile technologies provide opportunities for designing novel learning experiences that move out of the classroom. Information can be presented and interacted with in a variety of ways while exploring a physical environment. A key issue this raises is when, where, what and how much? Our research is concerned with the design, delivery and interaction of digital information when learning about ecology outdoors. We present a framework of the different forms of digital augmentation and the different processes by which they can be accessed. Using the framework, we designed an outdoors learning experience, aimed at encouraging students to carry out contextualized scientific enquiry and to reflect on their interactions. Pairs of 11-12 year olds explored a woodland and were presented at certain times with different forms of digital augmentation. Our study showed that this kind of exploration promoted interpretation and reflection at a number of levels of abstraction.

A functional programming language can be taught successfully as a first language, but if there is no follow up the students do not appreciate the functional approach. Following discussions concerning this issue at the 1995 FPLE conference (Hartel & Plasmeijer, 1995), we decided to develop such a follow up by writing a book that teaches C to students who can write simple functional programs. This paper summarises the essence of our approach, which is based on program transformation, and presents our experience teaching functional C at the Universities of Southampton and Bristol.

The determinism of instruction cache performance can be considered a major problem in multimedia devices which hope to maximise their quality of service. If instructions are evicted from the cache by competing blocks of code, the running application will take significantly longer to execute than if the instructions were present. Since it is difficult to predict when this interference will occur the performance of the algorithm at a given point in time is unclear We propose the use of an automatically configured partitioned cache to protect regions of the application code from each other and hence minimise interference. As well as being specialised to the purpose of providing predictable performance, this cache can be specialised to the application being run, rather than for the average case, using simple compiler algorithms.

Image segmentation is the first stage of processing in many practical computer vision systems. While development of particular segmentation algorithms has attracted considerable research interest, relatively little work has been published on the subject of their evaluation. In this paper we propose a framework for quantitative evaluation of segmentation algorithms which we believe addresses shortcomings of previous approaches, and use this framework to compare several state-of-the-art algorithms.

In this paper we investigate the combination of multitasking and multithreading in a (virtual) shared memory parallel machine running a number of parallel applications. In particular, we investigate whether it is better to run related threads, or unrelated threads on each node to achieve the best system throughput and to complete a mix of applications as quickly as possible. The experiments provide results for a range of mixes of applications. One of our benchmarks has a clear preference to place its threads across the whole machine, while the others have a slight preference to run their threads on smaller partitions of the machine. The differences are mostly slight, suggesting that the system scheduler has considerable flexibility in thread placement without jeopardising performance.

Abstract Our toolkit for the design and implementation of parallel functional programs supports the stepwise development of parallel programs from a high level sequential specification to an optimised parallel implementation. The toolkit is used as follows: The algorithm to be implemented is specified in a functional language. The program is debugged and tested using an interpreter. The program is compiled for a sequential machine. Its performance is analysed and improved. Annotation‐driven transformations are applied to the program to indicate parallel tasks. Simulations at task level, basic block level and bus transaction level make it possible to analyse the parallel performance of the program at three levels of detail. When the performance is optimised using the simulators, the program is executed on a genuine parallel machine. Several programs have been developed with the toolkit. A program that simulates tidal flow in an estuary of the North sea is presented as a case study to demonstrate the merits of the toolkit when developing complex parallel programs. The toolkit not only supports the design of parallel applications, it also allows the study of important concepts in parallel computer architecture. These include the behaviour of cached memory systems, bus protocols, scheduling algorithms and memory management algorithms.