Abstract: Current superscalar microprocessors are able to operate at a peak performance of up to 1 GFlop/sec. However, current main memory technology does not provide the data needed fast enough to keep the CPU busy. To minimize idle times of the CPU, caches are used to speed up accesses to frequently used data. To exploit caches, the software must be aware of them and reuse data in the cache before it is being replaced. Unfortunately, all conventional multigrid codes are not cache-aware and hence exploit less than 10 percent of the peak performance of cache based machines. Our studies with linear PDEs with constant coefficients show that it is possible to speed up the execution of our multigrid method by a large factor and hence solve a Poisson’s equation with one million unknowns in less than 3 seconds. The optimized reuse of data in the cache allows us to exploit 30 percent of the peak performance of the CPU, in contrast to mgd9v for instance, which achieves less than 5 percent on the same machine. To achieve this, we used several techniques like loop unrolling and loop fusion to better exploit the memory hierarchy and the superscalar CPU. We study the effects of these techniques on the runtime performance in detail. We also study several tools which guide the optimizations and help to restructure the code.

Abstract: A multi-clip query requests multiple video clips. We address the multi-clip query optimization problem. We propose a new heuristic called restricted search interval that maximizes clip sharing between queries and consequently reduces the workload of the video server. The experimental results show that the suggested heuristics reduce the server workload by about 68.7% in comparison to a classical heuristic approach.

Abstract: This paper presents the parallel video server SESAME-KB, by the means of its architectural design, striping, scheduling, caching and admission policy. Furthermore we compare our prototype to approaches which influenced our realization. Keywords: Parallel Video Server, Parallel Systems and Communication.

Abstract: This paper compares different selected and representative parallel video servers, including our server SESAME-KB, by the means of their architectural design, striping, scheduling, caching and admission policy. It is shown that these parallel video servers can support a high number of concurrent accesses, but will also reveal missing components, as bottlenecks. Finally we point to further developments

Abstract: The Multimedia Storage and Retrieval System described in this paper is aimed at storing and retrieving medical multimedia data such as images and videos. There are three significant problems that automatically need to be addressed: providing enough capacity to fit Terabytes of MPEG files, efficient extraction of video fragments from MPEG files and quality of service issues. We are working on two different approaches to build MMSRS. The first one, described in this article, utilizes commercial HSM software for managing the tertiary storage hardware. The second approach that we have started to investigate is an attempt to build a specialised storage management system from scratch.

Abstract: This paper focuses on parallel query optimization. We consider the operator problem and introduce a new class of execution strategies called Linear-oriented Bushy Trees (LBT). Compared to the related approach of the General Bushy Trees (GBT) a significant complexity reduction of the operator ordering problem can be derived theoretically and demonstrated experimentally (e.g. compared with GBTs, LBTs authorize optimization time improvement that can reach up to 49%) without losing quality. Finally we demonstrate that existing commercial parallel query optimizers need little extension mod ifications in order to handle LBTs.

Abstract: This paper describes an unconventional way to apply a performance analysis tool for parallel programs (Vampir) to understand and tune the performance of the real-time voice and data communication software running on top of Frequentis’ V4 switch. The execution schedule of the strictly time-triggered V4 switching software is computed off-line; analyzing the schedule to identify e.g. performance bottlenecks used to be a complex and time-consuming process. We present our approach to transform the V4 software schedule’s information into Vampir trace files and use this tool’s facilities to provide a visualization of the schedule. A case study illustrates the benefits of this approach.

Abstract: The Virtual Interface (VI) Architecture standard was developed to satisfy the need for a high-throughput, low-latency communication system required for cluster computing. This paper presents the results of a performance study of one VI Architecture hardware implementation, the Giganet cLAN (Cluster LAN). The focus of the study is to assess and compare the performance of different VI Architecture data transfer modes and specific features that are available to higher-level communication software like MPI, in order to aid the implementor to decide which VI Architecture options to employ for various communication scenarios. Examples of such options include the use of send/receive vs. RDMA data transfers, polling vs. blocking to check completion of communication operations, multiple VIs, completion queues, and scatter capabilities of VI Architecture.

Abstract: Niklaus Wirth is one of the great pioneers of computer technology and winner of the ACM ’s A.M.Turing Award,the most prestigious award in computer science. He has made substantial contributions to the development of programming languages, compiler construction, programming methodology, and hardware design. While working at ETH Zürich, he developed the languages Pascal and Modula-2. He also designed an early high performance workstation, the Personal Computer Lilith, and most recently the language and operating system Oberon. While Wirth has often been praised for his excellent work as a language designer and engineer, he is also an outstanding educator — something for which he is not as well known. This book brings together prominent computer scientists to describe Wirth’s contributions to education. With the exception of some of his colleagues such as Professors Dijkstra, Hoare, and Rechenberg, all of the contributors to this book are students of Wirth. The essays provide a wide range of contemporary views on modern programming practice and also illuminate the one persistent and pervasive quality found in all his work: his unequivocal demand for simple solutions. The authors and editors hope to pass on their enthusiasm for simple engineering solutions along with their feeling for a man to whom they are all so indebted.

Abstract: Es läuft eine spannende Diskussion darüber, wie früh man Kinder an den Computer heranführen sollte. Jenseits solcher Intellektuellen-Diskussionen machen manche Firmen schon seit Jahren enorme Geschäfte mit Software und Hardware für Kinder im Kindergartenalter. Auch der erste Computer für Babys hat schon seinen Siegeszug auf dem amerikanischen Markt angetreten. Mit den Geschäftemachern zu diskutieren, ist wahrscheinlich nicht viel klüger als gegen Windmühlen zu kämpfen. Diese Firmen könnten ihre Geschäfte nicht machen, wenn es nicht viele Eltern, Großeltern, Pädagogen und Psychologen gäbe, die den Computer kleinen Kindern mit guter Absicht in die Hand geben. Die folgende Diskussion spricht die wohlwollenden Erwachsenen an, die sich für Kinder verantwortlich fühlen und sich nicht entscheiden können, wann und wie Kinder mit dem Phänomen Computer konfrontiert werden sollten.