Computing and Informatics (E-Journal - Institute of Informatics, SAS, Bratislava)
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Stability and Strategic Time-Dependent Behaviour in Multiagent Systems
Get PDFTemporal reasoning and strategic behaviour are important abilities of multiagent systems. We introduce a game-theoretic framework suitable for modelling selfish and rational agents which can store and reason about the evolution of an environment, and act according to their interests. Our aim is to identify stable interactions: those where no agent has a benefit from changing his behaviour to another. For this reason we deploy the game-theoretic concept of Nash equilibrium and strong Nash equilibrium. We show that not all agent interactions can be stable. Also, we investigate the computational complexity for verifying and checking the existence of stable agent interactions. This paves the way for developing agents which can take appropriate decisions in competitive and strategic situations
Comparison of Latent Semantic Analysis and Probabilistic Latent Semantic Analysis for Documents Clustering
Get PDFIn this paper we compare usefulness of statistical techniques of dimensionality reduction for improving clustering of documents in Polish. We start with partitional and agglomerative algorithms applied to Vector Space Model. Then we investigate two transformations: Latent Semantic Analysis and Probabilistic Latent Semantic Analysis. The obtained results showed advantage of Latent Semantic Analysis technique over probabilistic model. We also analyse time and memory consumption aspects of these transformations and present runtime details for IBM BladeCenter HS21 machine
Supporting Dynamicity in Emergency Response Applications
Get PDFMultiagent Systems are a promising paradigm for software development. It is feasible to model such systems with many components where each one can solve a specific problem. This division of responsibilities allows multiagent systems to work in dynamically changing environments. An example of an environment that is very changeable is related with emergencies management. Emergency management systems depend on the cooperation of all their components due to their specialization. In order to obtain this cooperation, the components need to interact with each other and adapt their interactions depending on their purpose and the system components they are interacting with. Also, new components may arrive on the scene, which must be informed about the interaction policies that original components are using. Although Multiagent Systems are suited to managing scenarios of this kind, their effectiveness depends on their capacity to dynamically modify and adapt the protocols that control the interactions among agents in the system. In this paper, an infrastructure to support dynamically changing interaction protocols is presented
Agent-Based Cloud Resource Management for Secure Cloud Infrastructures
Get PDFThe cloud offers clear benefits for computations as well as for storage for diverse application areas. Security concerns are by far the greatest barriers to the wider uptake of cloud computing, particularly for privacy-sensitive applications. The aim of this article is to propose an approach for establishing trust between users and providers of cloud infrastructures (IaaS model) based on certified trusted agents. Such approach would remove barriers that prevent security sensitive applications being moved to the cloud. The core technology encompasses a secure agent platform for providing the execution environment for agents and the secure attested software base which ensures the integrity of the host platform. In this article we describe the motivation, concept, design and initial implementation of these technologies
A GPU-Based Parallel-Agent Optimization Approach for the Service Coverage Problem in UMTS Networks
Get PDFIn the context of coverage planning and control, the power of the common pilot channel signal determines the coverage area of a network cell. It also impacts the network capacity and thus the quality of service. We consider the problem of minimizing the total amount of pilot power subject to a full coverage constraint. Our optimization approach, based on parallel autonomous agents, gives very good solutions within an acceptable amount of time. The parallel implementation takes full advantage of GPU hardware in order to achieve impressive speed-up. We report the results of our experiments for three UMTS networks of different sizes based on a real network currently deployed in Slovenia
Optimization of a Parallel CFD Code and Its Performance Evaluation on Tianhe-1A
Get PDFThis paper describes performance tuning experiences with a parallel CFD code to enhance its performance and flexibility on large scale parallel computers. The code solves the incompressible Navier-Stokes equations based on the novel Slightly Compressible Model on three-dimensional structure grids. High level loop transformations and argument based code specialization are utilized to optimize its uniprocessor performance. Static arrays are converted into dynamically allocated arrays to improve the flexibility. The grid generator is coupled with the flow solver so that they can exchange grid data in the memory. A detailed performance evaluation is performed. The results show that our uniprocessor optimizations improve the performance of the flow solver for 1.38 times to 3.93 times on Tianhe-1A supercomputer. In memory grid data exchange optimization speeds up the application startup time by nearly two magnitudes. The optimized code exhibits an excellent parallel scalability running realistic test cases. On 4 096 CPU cores, it achieves a strong scaling parallel efficiency of 77.39 % and a maximum performance of 4.01 Tflops
Metascheduling and Heuristic Co-Allocation Strategies in Distributed Computing
Get PDFIn this paper, we address problems of efficient computing in distributed systems with non-dedicated resources including utility grid. There are global job flows from external users along with resource owner's local tasks upon the resource non-dedication condition. Competition for resource reservation between independent users, local and global job flows substantially complicates scheduling and the requirement to provide the necessary quality of service. A metascheduling concept, justified in this work, assumes a complex combination of job flow dispatching and application-level scheduling methods for parallel jobs, as well as resource sharing and consumption policies established in virtual organizations and based on economic principles. We introduce heuristic slot selection and co-allocation strategies for parallel jobs. They are formalized by given criteria and implemented by algorithms of linear complexity on an available slots number
An Ontological Framework for Context-Aware Collaborative Business Process Formulation
Get PDFIn cross-enterprise collaborative environment, we have dealt with challenges in business process integration for common business goals. Research directions in this domain range from business to business integration (B2Bi) to service-oriented augmentation. Ontologies are used in Business Process Management (BPM) to reduce the gap between the business world and information technology (IT), especially in the context of cross enterprise collaboration. For a dynamic collaboration, virtual enterprises need to establish collaborative processes with appropriate matching levels of tasks. However, the problem of solving the semantics mismatching is still not tackled or even harder in case of querying space between different enterprise profiles as considered as ontologies. This article presents a framework based on the ontological and context awareness during the task integration and matching in order to form collaborative processes in the manner of cross enterprise collaboration
Visualization of Aircraft Longitudinal-Axis Motion
Get PDFIn this paper, the use of continuous mathematical models of an aircraft in an aircraft simulator is described. The models are of lower degree and less time-consuming for calculation. Computer implementation of the models capable to work faster and more accurately and efficiently is also described. The suggested approach allows to achieve the required precision at accelerated simulation speed using the continuous mathematical models of an aircraft. Frequency of the computation of continuous mathematical models of an aircraft is higher, reaching up to 200 times per second. The main focus of the paper is designing continuous mathematical models of an aircraft, their simulation and visualization in aircraft simulators. Current mathematical models of a control of objects motion are based on aircraft aerodynamics. In our approach, these models have impact on the quality and completeness of simulation process and are crucial for computer modeling and visualization of equations of the continuous mathematical models of an aircraft. In the paper, creating continuous mathematical models of an aircraft and the way of visualization of simulation results are described in detail. The main aim of computer simulation of continuous mathematical models of an aircraft is pilots training. Aircraft simulator plays a key role in the process of pilots training; it enables pilots to control the aircraft and its equipment. Standard computer with a graphic processing unit for the visualization results from continuous mathematical models of an aircraft can be utilized