Nazareno Andrade

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Available grid technologies like the Globus Toolkit make possible for one to run a parallel application on resources distributed across several administrative domains. Most grid computing users, however, don’t have access to more than a handful of resources onto which they can use this technologies. This happens mainly because gaining access to resources(More)
eScience is rapidly changing the way we do research. As a result, many research labs now need non-trivial computational power. Grid and voluntary computing are well-established solutions for this need. However, not all labs can effectively benefit from these technologies. In particular, small and medium research labs (which are the majority of the labs in(More)
We collect BitTorrent usage data across multiple file-sharing communities and analyze the factors that affect users' cooperative behavior. We find evidence that the design of the BitTorrent protocol results in increased cooperative behavior over other P2P protocols used to share similar content (e.g. Gnutella). We also investigate two additional(More)
BitTorrent is a widely popular peer-to-peer content distribution protocol. Unveiling patterns of resource demand and supply in its usage is paramount to inform operators and designers of BitTorrent and of future content distribution systems. This study examines three BitTorrent content-sharing communities regarding resource demand and supply. The resulting(More)
Bag-of-Tasks applications (those parallel applications whose tasks are independent) are both relevant and amendable for execution on computational grids. In fact, one can argue that Bag-of-Tasks applications are the applications most suited for grids, where communication can easily become a bottleneck for tightly-coupled parallel applications. In spite of(More)
Q&A sites currently enable large numbers of contributors to collectively build valuable knowledge bases. Naturally, these sites are the product of contributors acting in different ways - creating questions, answers or comments and voting in these - contributing in diverse amounts, and creating content of varying quality. This paper advances present(More)
Currently, most computational grids (systems allowing transparent sharing of computing resources across organizational boundaries) are assembled using human negotiation. This procedure does not scale well, and is too inflexible to allow for large open grids. Peer-to-peer grids present an alternative way to build grids with many sites. However, to actually(More)
The efficiency of BitTorrent in disseminating content has inspired a number of P2P protocols for on-demand video streaming (VoD). Prior work on adapting BitTorrent to VoD mainly focused on the piece selection policy, since streaming requires a somewhat “in order” download progress. Conversely, not much effort has been spent into adapting BitTorrent’s peer(More)
In tagging systems users can annotate items of interest with free-form terms. A good understanding of usage characteristics of such systems is necessary to improve the design of current and next generation of tagging systems. To this end, this work explores three aspects of user behavior in <i>CiteULike</i> and <i>Connotea</i>, two systems that include(More)