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Ioannis Giannakopoulos

Publications and source records attributed to Ioannis Giannakopoulos.

2 recordsLinked to original sources

Graph Operator Modeling over Large Graph Datasets

As graph representations of data emerge in multiple domains, data analysts need to be able to intelligently select among a magnitude of different data graphs based on the effects different graph operators have on them. Exhaustive execution of an operator over the bulk of available data sources is impractical due to the massive resources it requires. Additionally, the same process would have to be re-implemented whenever a different operator is considered. To address this challenge, this work proposes an efficient graph operator modeling methodology. Our novel approach focuses on the inputs themselves, utilizing graph similarity to infer knowledge about input graphs. The modeled operator is only executed for a small subset of the available graphs and its behavior is approximated for the rest of the graphs using machine learning techniques. Our method is operator-agnostic, as the same similarity information can be reused for modeling multiple graph operators. We also propose a family of similarity measures based on the degree distribution that prove capable of producing high quality estimations, comparable or even surpassing other much more costly, state-of-the-art similarity measures. Our evaluation over both real-world and synthetic graphs indicates that our method achieves extremely accurate modeling of many commonly encountered operators, managing massive speedups over a brute-force alternative.

cs.SI↗

A Decision Tree Based Approach Towards Adaptive Profiling of Distributed Applications

The adoption of the distributed paradigm has allowed applications to increase their scalability, robustness and fault tolerance, but it has also complicated their structure, leading to an exponential growth of the applications' configuration space and increased difficulty in predicting their performance. In this work, we describe a novel, automated profiling methodology that makes no assumptions on application structure. Our approach utilizes oblique Decision Trees in order to recursively partition an application's configuration space in disjoint regions, choose a set of representative samples from each subregion according to a defined policy and return a model for the entire space as a composition of linear models over each subregion. An extensive evaluation over real-life applications and synthetic performance functions showcases that our scheme outperforms other state-of-the-art profiling methodologies. It particularly excels at reflecting abnormalities and discontinuities of the performance function, allowing the user to influence the sampling policy based on the modeling accuracy and the space coverage.

cs.DC↗