Beltway: Getting Around Garbage Collection Gridlock

We present the design and implementation of a new garbage collection framework that significantly generalizes existing copying collectors. The Beltway framework exploits and separates object age and incrementality. It groups objects in one or more increments on queues called belts, collects belts independently, and collects increments on a belt in first-in-first-out order. We show that Beltway configurations, selected by command line options, act and perform the same as semi-space, generational, and older-first collectors, and encompass all previous copying collectors of which we are aware. The increasing reliance on garbage collected languages such as Java requires that the collector perform well. We show that the generality of Beltway enables us to design and implement new collectors that are robust to variations in heap size and improve total execution time over the best generational copying collectors of which we are aware by up to 40%, and on average by 5 to 10%, for small to moderate heap sizes. New garbage collection algorithms are rare, and yet we define not just one, but a new family of collectors that subsumes previous work. This generality enables us to explore a larger design space and build better collectors

The Federal Design of a Central Bank in a Monetary Union: The Case of the European System of Central Banks

In this paper we analyze the European System of Central Banks (ESCB) as a federal central bank system. First, the degree of decentralization of the ESCB will be briefly compared with its predecessor, the Deutsche Bundesbank, and its counterweight in the US, the Federal Reserve System. Moreover, the development during the period 1990-99 of the total, economics and research staffing of the ECB and the national central banks in the EU will be investigated and also the staff ratios of the national central banks in 1999. Furthermore, the research activities of the central banks in the European Union over the period 1990-99 will be analyzed both in terms of input (economics and research staff) and output (quality-weighted number of articles in scientific journals). The share of economics research staff in total staff of the national central banks varies between 0.02 and 0.17. The ECB has the highest ratio between economists and researchers and other staff. A ranking of research performance based on the quality-weighted number of scientific articles per economics and research employee reveals that the Bank of Finland has the best research performance of European central banks, followed by De Nederlandsche Bank, the Banco de Portugal and the Oesterreichische Nationalbank. There is only a weak relationship between the research performance and the share of research staff. The conclusion "small is beautiful" also seems to hold for the economics and research departments of the European central banks.

Issues in using commodity operating systems for time-dependent tasks: experiences from a study of windows NT

ManuscriptThis paper presents a snapshot of early results from a study of Windows NT aimed at understanding and improving its limitations when used for time-dependent tasks, such as those that arise for audio and video processing. Clearly there are time scales for which it can achieve effectively perfect reliability, such as the onesecond deadlines present in the Tiger Video Filesystem. Other time scales, such as reliable sub-millisecond scheduling of periodic tasks in user space, are clearly out of reach. Yet, there is an interesting middle ground between these time scales in which deadlines may be met, but will not always be. This study focuses on system and application behaviors in this region with the short-term goals of understanding and improving the real-time responsiveness of applications using Windows NT 5.0 and a longer-term goal of prototyping and recommending possible scheduling and resource management enhancements to future Microsoft systems products. Finally, while this paper primarily contains examples and results from Windows NT, we believe that the kinds of limitations and artifacts identified may also apply to other commodity systems such as the many UNIX variants. Indeed, this paper is primarily intended to provide a starting point for fruitful discussions along these lines at the workshop and not as a record of completed work

The IRIS Network of Excellence:: Integrating Research in Interactive Storytelling

Abstract. Interactive Storytelling is a major endeavour to develop new media which could offer a radically new user experience, with a potential to revolutionise digital entertainment. European research in Interactive Storytelling has played a leading role in the development of the field, and this creates a unique opportunity to strengthen its position even further by structuring collaboration between some of its main actors. IRIS (Integrating Research in Interactive Storytelling) aims at creating a virtual centre of excellence that will be able to progress the understanding of fundamental aspects of Interactive Storytelling and the development of corresponding technologies

The problems you're having may not be the problems you think you're having: results from a latency study of windows NT

ManuscriptThis paper is intended to catalyze discussions on two intertwined systems topics. First, it presents early results from a latency study of Windows NT that identifies some specific causes of long thread scheduling latencies, many of which delay the dispatching of runnable threads for tens of milliseconds. Reasons for these delays, including technical, methodological, and economic are presented and possible solutions are discussed. Secondly, and equally importantly, it is intended to serve as a cautionary tale against believing one's own intuition about the causes of poor system performance. We went into this study believing we understood a number of the causes of these delays, with our beliefs informed more by conventional wisdom and hunches than data. In nearly all cases the reasons we discovered via instrumentation and measurement surprised us. In fact, some directly contradicted "facts" we thought we "knew"

On the effectiveness of run-time checks

Run-time checks are often assumed to be a cost-effective way of improving the dependability of software components, by checking required properties of their outputs and flagging an output as incorrect if it fails the check. However, evaluating how effective they are going to be in a future application is difficult, since the effectiveness of a check depends on the unknown faults of the program to which it is applied. A programming contest, providing thousands of programs written to the same specifications, gives us the opportunity to systematically test run-time checks to observe statistics of their effects on actual programs. In these examples, run-time checks turn out to be most effective for unreliable programs. For more reliable programs, the benefit is relatively low as compared to the gain that can be achieved by other (more expensive) measures, most notably multiple-version diversity

Aspect-oriented interaction in multi-organisational web-based systems

Separation of concerns has been presented as a promising tool to tackle the design of complex systems in which cross-cutting properties that do not fit into the scope of a class must be satisfied. Unfortunately, current proposals assume that objects interact by means of object-oriented method calls, which implies that they embed interactions with others into their functional code. This makes them dependent on this interaction model, and makes it difficult to reuse them in a context in which another interaction model is more suited, e.g., tuple spaces, multiparty meetings, ports, and so forth. In this paper, we show that functionality can be described separately from the interaction model used, which helps enhance reusability of functional code and coordination patterns. Our proposal is innovative in that it is the first that achieves a clear separation between functionality and interaction in an aspect-oriented manner. In order to show that it is feasible, we adapted the multiparty interaction model to the context of multiorganisational web-based systems and developed a class framework to build business objects whose performance rates comparably to handmade implementations; the development time, however, decreases significantly.Comisión Interministerial de Ciencia y Tecnología TIC2000-1106-C02-0