Viser treff 621-640 av 640

    • Evaluating the performance of the allreduce collective operation on clusters. Approach and results 

      Bongo, Lars Ailo; Anshus, Otto J.; Bjørndalen, John Markus (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 

      Fjeld, Frode V. (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 

      Khalaila, Ahmad H.; Eliassen, Frank (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 

      Fjeld, Frode V. (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 

      Khalaila, Ahmad; Eliassen, Frank (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 

      Renesse, Robbert van; Kvalnes, Aage; Johansen, Dag; Arnesen, Audun (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 

      Bongo, Lars Ailo; Anshus, Otto J.; Bjørndalen, John Markus (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. 

      Jacobsen, Kjetil; Johansen, Dag (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 ...
    • Pesto flavoured security 

      Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, 2002-05)
      Pesto aims at providing highly available and secure storage for longlived data to mobile users roaming into untrusted environments. Security in Pesto encompasses the following three aspects: availability, safety, and privacy. A mechanism supporting one aspect may adversely affect another. For example, replication may increase availability but complicates supporting confidentiality, and simply ...
    • An approach towards an agent computing environment 

      Marzullo, Keith; Johansen, Dag; Lauvset, Kåre J. (Research report; Forskningsrapport, 1998)
      We devise a mobile agent middleware architecture for supporting distributed applications in a wide-area network. The architecture provides a structural framework for functional components that are needed to support mobile agents in asymmetric networking environments.
    • The taste of Pesto 

      Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, 2001-08)
      The Pesto distributed storage platform is geared towards a computing model where private machines play a pivotal r ˆ ole. We argue that no centralized solutions are acceptable in its design and that it supports allocation of separate tasks to separate system components found in its target environment. Hence, Pesto separates trust from responsibility, storage from access control policy, and ...
    • The Pesto project. Goals and motivation 

      Dillema, Feike W.; Stabell-Kulø, Tage (Research report; Forskningsrapport, 2001-06)
      Pesto is a storage system geared towards a computing model where private machines play a pivotal role. Sharing of data is crucial, both between partners, and between the many devices owned by individual users. Replication is the only sensible means to provide ubiquitous access to private data. However, without provisions, replication endangers privacy by enlarging the Trusted Computing Base. The ...
    • Authorization and access control in a distributed file repository 

      Arild, Ronny; Stabell-Kulø, Tage (Research report; Forskningsrapport, 1999-01-18)
      A distributed file repository is described. It supports interaction between different machines used by a single user, as well as between users that share data. Files can be replicated and consistency will be maintained, or files can be shipped (copied) to a remote site. As with more traditional systems, the servers are trusted not to leak information. However, the rôle servers play is not as much ...
    • Some hints on the theory and practice of authentication in distributed systems 

      Stabell-Kulø, Tage; Bottoni, Andrea (Research report; Forskningsrapport, 2003-05-17)
      Authentication in Distributed Systems: Theory and Practice provides considerable insight. However, it can be hard to read, as many details are left out, probably for brevity; it is still 45 pages long. We provide detailed explanations of tricky points.
    • TOS: A Kernel of a Distributed Systems Management System 

      Marzullo, Keith; Lauvset, Kåre J.; Johansen, Dag (Research report; Forskningsrapport, 2000-03-02)
      Distributed systems are becoming harder to manage, in part because the uses we put to distributed systems are rapidly changing. Hence, the software used to manage a distributed system needs to be flexible enough to accommodate these new uses. It also has to be secure enough to not allow unauthorized changes to be made to the system. We present a library and a kernel that supports the management ...
    • Adding mobility to non-mobile web robots 

      Sudmann, Nils P.; Johansen, Dag (Research report; Forskningsrapport, 2000)
      In this paper we will show that it is possible to combine mobile agent technology with existing non-mobile data mining applications. The motivation for this is the advantage mobile agents offer in moving the computation closer to the data in a distributed system. This can save bandwidth and increase performance when the data is condensed as a result of data mining.
    • Kontekstsensitiv tilpasning av interaksjonsmodi mot mobile terminaler 

      Henriksen, André (Master thesis; Mastergradsoppgave, 2003-12-15)
      Denne oppgaven ser på mulighetene for å bruke kontekstinformasjon for å kunne tilpasse interaksjonsmodi mot mobile terminaler, spesielt mobiltelefoner. Hensikten er å illustrere hvordan brukere av et transportselskap automatisk kan motta beskjeder om forsinkelser på bussavganger han/hun er interessert i, samt andre beskjeder fra transportselskapet. Brukere skal altså slippe å kjenne til vanlige ...
    • p-SARS: Peer-to-peer search for a recommender system 

      Devik, Rune (Master thesis; Mastergradsoppgave, 2003-12-15)
      WAIF started out in 2002 and the overall goal is to make the computers automatically search for relevant information based on the user’s preferences, and to push this information directly to the user wherever he/she is and to whatever device he/she has available. In other words, make the machines serve us, with as little human interaction as possible. This thesis focuses on a specific part of this ...
    • FAT: A framework for automated regression testing of protocol stacks 

      Nilsen, Karl Magnus (Master thesis; Mastergradsoppgave, 2003-12-15)
      Software systems today are becoming larger and more complex, resulting in a growing need for good and efficient testing routines. An approach used by several software developers is to automate the test process. Test automation has the benefits that it reduces the time of the testing process and that automated tests are more accurate and precise than manual tests. <br /><br /> Manufacturers who ...
    • Frag: A distributed approach to display wall gaming 

      Grammeltvedt, Åsmund (Master thesis; Mastergradsoppgave, 2006-06-01)
      Computer games with distributed functionality, such as most modern multiplayer games, provide a rich environment in which one can experiment with high performance distribution of computational and graphical resources. Their extremely high requirements for processing power and consistent visual output create a platform with unique demands. Current tiled display walls provide, as a consequence of ...