George Stelle

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An emerging consensus among policy makers is that interventions undertaken by Internet Service Providers are the best way to counter the rising incidence of malware. However, assessing the suitability of countermeasures at this scale is hard. In this paper, we use an agent-based model, called ASIM, to investigate the impact of policy interventions at the(More)
There are few studies that look closely at how the topology of the Internet evolves over time; most focus on snapshots taken at a particular point in time. In this paper, we investigate the evolution of the topology of the Autonomous Systems graph of the Internet, examining how eight commonlyused topological measures change from January 2002 to January(More)
Malware spread among websites and between websites and clients is an increasing problem. Search engines play an important role in directing users to websites and are a natural control point for intervening using mechanisms such as blacklisting. The paper presents a simple Markov model of malware spread through large populations of websites and studies the(More)
Disruptive changes to computer architecture are paving the way toward extreme scale computing. The co-design strategy of collaborative research and development among computer architects, system software designers, and application teams can help to ensure that applications not only cope but thrive with these changes. In this paper, we present a novel(More)
We introduce a task-parallel algorithm for sparse incomplete Cholesky factorization that utilizes a 2D sparse partitioned-block layout of a matrix. Our factorization algorithm follows the idea of algorithms-by-blocks by using the block layout. The algorithm-byblocks approach induces a task graph for the factorization. These tasks are inter-related to each(More)
Existing machines for lazy evaluation use a flat representation of environments, storing the terms associated with free variables in an array. Combined with a heap, this structure supports the shared intermediate results required by lazy evaluation. We propose and describe an alternative approach that uses a shared environment to minimize the overhead of(More)
This paper describes improvements in task scheduling for the Chapel parallel programming language provided in its default on-node tasking runtime, the Qthreads library. We describe a new scheduler distrib which builds on the approaches of two previous Qthreads schedulers, Sherwood and Nemesis, and combines the best aspects of both --work stealing and load(More)
Tracking Internet censorship is challenging because what content the censors target can change daily, even hourly, with current events. The process must be automated because of the large amount of data that needs to be processed. Our focus in this paper is on automated probing of keyword-based Internet censorship, where natural language processing(More)
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