1,720,960 research outputs found
Generalized Nash Equilibria for the Service Provisioning Problem in Cloud Systems
Full text linkRecently, the evolution and widespread adoption of virtualization, SOA, autonomic, and utility computing have converged letting a new paradigm to emerge: Cloud computing. Currently the Cloud offer is becoming wider and wider, since all the major IT Companies and Service providers have started providing solutions. As Cloud-based services are more numerous and dynamic, the development of efficient service provisioning policies becomes increasingly challenging. In this paper we take the perspective of SaaS providers which host their applications at an IaaS. Each SaaS needs to comply with QoS requirements, specified in SLA contracts with the end-users, which determine the revenues and penalties on the basis of the achieved performance level. SaaS providers want to maximize their revenues from SLAs, while competing and bidding for the use of infrastructural resources. In this paper we model the service provisioning problem as a generalized Nash game and we show the existence of equilibria for such game. Moreover, we propose two solution methods based on the best-reply dynamics and we prove their convergence in a finite number of iterations to a generalized Nash equilibrium. We demonstrate the effectiveness of our approach by simulation and performing tests on a real prototype environment deployed on Amazon EC2
A Game Theoretic Formulation of the Service Provisioning Problem in Cloud Systems
No full textCloud computing is an emerging paradigm which allows the on-demand delivering of software, hardware, and data as services. As cloud-based services are more numerous and dynamic, the development of efficient service provisioning policies become increasingly challenging. Game theoretic approaches have shown to gain a thorough analytical under- standing of the service provisioning problem.
In this paper we take the perspective of Software as a Service (SaaS) providers which host their applications at an Infrastructure as a Service (IaaS) provider. Each SaaS needs to comply with quality of service requirements, spec- ified in Service Level Agreement (SLA) contracts with the end-users, which determine the revenues and penalties on the basis of the achieved performance level. SaaS providers want to maximize their revenues from SLAs, while minimiz- ing the cost of use of resources supplied by the IaaS provider. Moreover, SaaS providers compete and bid for the use of in- frastructural resources. On the other hand, the IaaS wants to maximize the revenues obtained providing virtualized re- sources. In this paper we model the service provisioning problem as a Generalized Nash game, and we propose an efficient algorithm for the run time management and alloca- tion of IaaS resources to competing SaaSs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Service Provisioning on the Cloud: Distributed Algorithms for Joint Capacity Allocation and Admission Control
No full textCloud computing represents a new way to deliver and use services on a shared IT infrastructure. Traditionally, IT hardware and software were acquired and provisioned on business premises. Software applications were built, possibly integrating off-the-shelf components, deployed and run on these privately owned resources. With service-oriented computing, applications are offered by service providers to clients, who can simply invoke them through the network. The offer specifies both the functionality and the Quality of Service (QoS). Providers are responsible for deploying and running services on their own resources. Cloud computing moves one step further. Computing facilities can also be delivered on demand in the form of services over a network. In this paper we take the perspective of a Software as a Service (SaaS) provider whose goal is to maximize the revenues from end users who access services on a pay-per-use basis. In turn, the SaaS provider exploits the cloud, which provides an Infrastructure as a Service (IaaS), where the service provider dynamically allocates hardware physical resources.
This paper presents a distributed algorithm for run-time management of SaaS cloud systems that jointly addresses the capacity allocation and admission control of multiple classes of applications providing an heuristic solution which closely approximates the global optimal solution
Energy-aware Autonomic Resource Allocation in Multi-tier Virtualized Environment
No full textWith the increase of energy consumption associated with IT infrastructures, energy management is becoming a priority in the design and operation of complex service-based systems. At the same time, service providers need to comply with Service Level Agreement (SLA) contracts which determine the revenues and penalties on the basis of the achieved performance level. This paper focuses on the resource allocation problem in multitier virtualized systems with the goal of maximizing the SLAs revenue while minimizing energy costs. The main novelty of our approach is to address—in a unifying framework—service centers resource management by exploiting as actuation mechanisms allocation of virtual machines (VMs) to servers, load balancing, capacity allocation, server power state tuning, and dynamic voltage/frequency scaling. Resource management is modeled as an NP-hard mixed integer nonlinear programming problem, and solved by a local search procedure. To validate its effectiveness, the proposed model is compared to top-performing state-of-the-art techniques. The evaluation is based on simulation and on real experiments performed in a prototype environment. Synthetic as well as realistic workloads and a number of different scenarios of interest are considered. Results show that we are able to yield significant revenue gains for the provider when compared to alternative methods (up to 45 percent). Moreover, solutions are robust to service time and workload variations
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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