130,536 research outputs found
Characterization of the evolution a news Web site
No full textThe Web has become a ubiquitous tool for distributing knowledge and information and for conducting businesses. To exploit the huge potential of the Web as a global information repository, it is necessary to understand its dynamics. These issues are particularly important for news Web sites as they are expected to provide fresh information on current world events to a potentially large user population. This paper presents an experimental study aimed at characterizing and modeling the evolution of a news Web site. We focused on the MSNBC Web site as it is a good representative of its category in terms of structure, news coverage and popularity. Specifically, we analyzed how often and to what extent the content of this site changed and we identified models describing its dynamics. The study has shown that the rate of page creations and updates was characterized by some well defined patterns that varied as a function of time of day and day of week. On the contrary, the content of individual pages changed to a different extent. Most updates involved a very small fraction of their content, whereas very few were more extensive and spread over the whole page. By taking into accounts all these aspects, we derived analytical models able to accurately capture and reproduce the evolution of the news Web site
Workload Characterization: A Survey Revisited
No full textWorkload characterization is a well-established discipline that plays a key role in many performance en-
gineering studies. The large-scale social behavior inherent in the applications and services being deployed
nowadays leads to rapid changes in workload intensity and characteristics and opens new challenging
management and performance issues. A deep understanding of user behavior and workload properties and
patterns is therefore compelling. This article presents a comprehensive survey of the state of the art of
workload characterization by addressing its exploitation in some popular application domains. In particular,
we focus on conventional web workloads as well as on the workloads associated with online social networks,
video services, mobile apps, and cloud computing infrastructures. We discuss the peculiarities of these work-
loads and present the methodological approaches and modeling techniques applied for their characterization.
The role of workload models in various scenarios (e.g., performance evaluation, capacity planning, content
distribution, resource provisioning) is also analyzed
Redistribution strategies for portable parallel FFT: a case study
No full textThe best approach to parallelize multidimensional FFT algorithms has long been under debate, Distributed transposes are widely used, but they also vary in communication policies and hence performance. In this work we analyze the impact of different redistribution strategies on the performance of parallel FFT, on various machine architectures. We found that some redistribution strategies were consistently superior, while some others were unexpectedly inferior, An in-depth investigation into the reasons for this behavior is included in this work. Copyright (C) 2001 John Wiley & Sons, Ltd
An extensive study of Web robots traffic
No full textThe traffic produced by the periodic crawling activities of Web robots often represents a good fraction of the overall websites traffic, thus causing some non-negligible effects on their performance. Our study focuses on the traffic generated on the SPEC website by many different Web robots, including, among the others, the robots employed by some popular search engines. This extensive investigation shows that the behavior and crawling patterns of the robots vary
significantly in terms of requests, resources and clients involved in their crawling activities. Some robots tend to concentrate their requests in short periods of time and follow some sorts of deterministic patterns characterized by multiple peaks. The requests of other robots exhibit a time dependent behavior and repeated patterns with some periodicity. We represent the traffic as a time series modelled in the frequency domain. The identified models, consisting of trigonometric polynomials and Auto Regressive Moving
Average components, accurately summarize the behavior of the overall traffic as well as the traffic of individual robots.
These models can be easily used as a basis for forecasting
A Methodology Towards Automatic Performance Analysis of Parallel Applications
No full textTuning and debugging the performance of parallel applications is an iterative process consisting of several steps dealing with identification and localization of inefficiencies, repair, and verification of the achieved performance. In this paper, we address the analysis of the performance of parallel applications from a methodological viewpoint with the aim of identifying and localizing inefficiencies. Our methodology is based on performance metrics and criteria that highlight the properties of the applications and the load imbalance and dissimilarities in the behavior of the processors. A few case studies illustrate the application of the methodology
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