English
norskArtikler, rapporter og annet (informatikk): Recent submissions
Now showing items 441-460 of 468
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Performance experiments with the Storm View Distributed Parallel Volume Renderer.
(Research report; Forskningsrapport, 1995-06)Volume rendering is a useful but cpu-intensive method for visualizing large scalar fields. The time to render a single image may be reduced by parallel processing. This paper reports on performance experiments with the StormView volume renderer, which is parallelized on a set of 57 MIPS / 17 MFLOPS workstations connected by a 10 Mbps Ethernet. For certain user patterns, we show that our parallelization ... -
A Declarative Profile Model for Qos negotiation
(Research report; Forskningsrapport, 2005-12)In this report we define the semantics of a language for dynamic QoS expressions which can be evaluated at run-time for conformance. We define how expressions can be constructed from atomic expressions termed ’basic profiles’ using composition operators. Two such operators are defined: The sum ( ’+’ ) which corresponds to simple conjunction and component-sum (’Å’) which assume that the operands ... -
An introduction to the TACOMA distributed system. Version 1.0
(Research report; Forskningsrapport, 1995-06)This report briefly introduces TACOMA Version 1.0. This distributed system supports agents, computations that can roam the internet. The report presents the TACOMA project, the computational model, how to get started, and the basic TACOMA abstractions. -
The Longcut Wide Area Network Emulator. Design and Evaluation
(Research report; Forskningsrapport, 2005)Experiments run on a Grid, consisting of clusters administered by multiple organizations connected by shared wide area networks (WANs), may not be reproducible. First, traffic on the WAN cannot be controlled. Second, allocating the same resources for subsequent experiments can be difficult. Longcut solves both problems by splitting a single cluster into several parts, and for each part having one ... -
The last hop of global notification delivery to mobile users. Matching preferences, context, and device constraints.
(Research report; Forskningsrapport, 2004)Events injected by publishers into a publish/subscribe system may reach users through a variety of devices: a stationary desktop, a laptop, a mobile phone, etc. We argue that the "last hop" -- from the network to the output device -- has unique properties, owing to the mobile nature of these devices, and as such demands special consideration. In particular, user's preferences and location may limit ... -
Efficient bill-of-materials algorithms
(Research report; Forskningsrapport, 1996-09-01)It has been shown that every linearly recursive database query can be expressed as a transitive closure possibly preceded and followed by relational algebraic operations. A large class of such queries computes the bill-of-materials of database relations. This paper presents efficient sequential and distributed algorithms that compute the bill-of-materials of a database relation. These algorithms ... -
ReflecTS: A reflective transaction service framework for open applications
(Research report; Forskningsrapport, 2004)Transactional middleware platforms must accommodate an increasingly diverse range of requirements from both applications and the underlying systems. It is clear that applications have characteristics and requirements that vary a lot, and that transactional middleware must be able to support the potential variety in transaction execution requirements. In this paper we describe ReflecTS, a reflective ... -
Security in the PASTA project
(Research report; Forskningsrapport, 1997-02-04)This paper presents the system model for the work on security in the Pasta project. We present the objectives of the security effort, the threats we will consider, and those we will not consider. As such, the paper describes the environment which applications must be prepared to face, and still provide users with the desired degree of privacy. -
Environment mobility. Moving the desktop around.
(Research report; Forskningsrapport, 2004)In this position paper, we focus on issues related to middleware support for software mobility in ad hoc and pervasive systems. In particular, we are interested in moving the computational environment of a mobile user following his trajectory. We present details of WAIFARER, a prototype implementation that automatically saves and restores application level state to support this mobility. Security, ... -
On the design and performance of the PARFUM Parallel Fault Tolerant Volume Renderer
(Research report; Forskningsrapport, 1997-01)Volume rendering is an important and CPU-intensive technique for visualizing large scalar fields. In essence, a volume renderer performs two activites on behalf of the user: loading a new data set, and rendering the current one. At one level, the performance of an individual activity is important. At another level, the erformance of the session as a whole, in particular switching from one activity ... -
A programmable structure for pervasive computing
(Research report; Forskningsrapport, 2004)This exstended abstract presents an asymmetric and programmable (extensible) approach to pervasive computing. The idea is to off-load computations from light portable clients into a back-bone of seamlessly integrated servers. This way, a user can extend and personalize his pervasive computational environment by installing computations following his trajectory throughout the day. Focus on this extended ... -
QoS applied to security in mobile computing
(Research report; Forskningsrapport, 1997-06-30)Hand-held mobile computers have the potential to become important communication tools for roaming users. As such, they will also become very personal. They will be used under a wide range of operating conditions, and tight user control will be enforced on issues like power consumption, consistency control, and trust management. Their ability to adapt will be the key to their success. In this paper ... -
Evaluating the performance of the allreduce collective operation on clusters. Approach and results
(Research report; Forskningsrapport, 2004)The performance of the collective operations provided by a communication library is important for many applications run on clusters. The communication structure of collective operations can be organized as a tree. Performance can be improved by configuring and mapping the tree to the clusters in use. We describe and demonstrate an approach for evaluating the performance of different configurations ... -
The Movitz development platform
(Research report; Forskningsrapport, 2003-12-19)We present a technical description of the Movitz development platform for stand-alone applications on the x86 PC architecture. -
Quick- instead of Merge-sort for pipelines systems
(Research report; Forskningsrapport, 1997-05)This paper proposes an external sorting algorithm for large data as an alternative to the widely used merge-sort algorithm. The algorithm we present is an application of the widely known quick-sort algorithm to large sequences of data stored externally on a disk device. The problem with the merge-sort algorithm is not its time complexity but the large amount of time it requires to output its first ... -
Using a waiting protocol to separate concerns in the mutual exclusion problem
(Research report; Forskningsrapport, 2003-11-21)How to implement process synchronization in a general-purpose software library while incurring a minimum of policy decisions on the system as a whole? We propose that in dealing with the problem of mutual exclusion in concurrent systems, a separation of concerns between the mechanism of detecting contention and the policy decision of what to do when such contention is detected is appropriate. We ... -
An efficient bill-of-materials algorithm
(Research report; Forskningsrapport, 1997-04)A large class of linear recursive queries compute the bill-of-materials of database relations.This paper presents a novel algorithm that computes the bill-of-materials of its argument's (database) relation. The algorithm uses a special join operation that accumulates the cost of composite parts, without constructing the transitive closure of the argument relation, thus saving time and space. We ... -
Vortex. An event-driven multiprocessor operating system supporting performance isolation
(Research report; Forskningsrapport, 2003-06-13)Vortex is a new multiprocessor operating system that is entirely event-driven. The Vortex kernel, as well as its applications, are structured as stagesthat communicate through event passing. Each stage is a small finite state machine. The event architecture is efficient and allows Vortex to balance load across the processors automatically. Vortex uses an Event Scheduling Tree (EST) on each CPU. ... -
Using a virtual event space to understand parallel application communication behavior
(Research report; Forskningsrapport, 2003)We have developed EventSpace, a configurable data collecting, management and observation system for monitoring low-level synchronization and communication events with the purpose of understanding the behavior of parallel applications on clusters and multi-clusters. Applications are instrumented by adding data collecting code in the form of event collectors to an applications communication paths. ... -
Mobile software on mobile hardware. Experiences with TACOMA on PDAs.
(Research report; Forskningsrapport, 1997)In this paper, we present experiences from adding software mobility to mobile, hand-held computers. In particular, we have built TACOMA Lite, a mobile code system, for this environment. With TACOMA Lite installed, hand-held computers can host and execute mobile code. TACOMA Lite has been used as platform for several mobile code applications. Through experience with these applications, we have derived ...
