Alessio and me presented our papers at KDD 2018 in London. It has been a very huge event. My first social dinner with more than 3 thousands sit participants.

The first paper is a joint work with Alessio Conte, Tiziano De Matteis, Daniele De Sensi, Roberto Grossi, and Luca Versari, with title “D2K: Scalable Community Detection in Massive Networks via Small-Diameter k-Plexes”.

This paper studies k-plexes, a well known pseudo-clique model for network communities. In a k-plex, each node can miss at most k-1 links. Our goal is to detect large communities in today’s real-world graphs which can have hundreds of millions of edges. While many have tried, this task has been elusive so far due to its computationally challenging nature: k-plexes and other pseudo-cliques are harder to find and more numerous than cliques, a well known hard problem. We present D2K, which is the first algorithm able to find large k-plexes of very large graphs in just a few minutes. The good performance of our algorithm follows from a combination of graph-theoretical concepts, careful algorithm engineering and a high-performance implementation. In particular, we exploit the low degeneracy of real-world graphs, and the fact that large enough k-plexes have diameter 2. We validate a sequential and a parallel/distributed implementation of D2K on real graphs with up to half a billion edges.

The second paper is a joint work with Alessio Conte, Gaspare Ferraro, Roberto Grossi, Kunihiko Sadakane, and Takeaki Uno with title “Node Similarity with q -Grams for Real-World Labeled Networks”

We study node similarity in labeled networks, using the label sequences found in paths of bounded length q leading to the nodes. (This recalls the q-grams employed in document resemblance, based on the Jaccard distance.) When applied to networks, the challenge is two-fold: the number of q-grams generated from labeled paths grows exponentially with q, and their frequency should be taken into account: this leads to a variation of the Jaccard index known as Bray-Curtis index for multisets. We describe nSimGram, a suite of fast algorithms for node similarity with q-grams, based on a novel blend of color coding, probabilistic counting, sketches, and string algorithms, where the universe of elements to sample is exponential. We provide experimental evidence that our measure is effective and our running times scale to deal with large real-world networks.