Browsing by Subject "Community detection"

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  • Reittu, Hannu; Norros, Ilkka; Räty, Tomi; Bolla, Marianna; Bazsó, Fülöp (Springer Berlin Heidelberg, 2019)
    Abstract We analyze the performance of regular decomposition, a method for compression of large and dense graphs. This method is inspired by Szemerédi’s regularity lemma (SRL), a generic structural result of large and dense graphs. In our method, stochastic block model (SBM) is used as a model in maximum likelihood fitting to find a regular structure similar to the one predicted by SRL. Another ingredient of our method is Rissanen’s minimum description length principle (MDL). We consider scaling of algorithms to extremely large size of graphs by sampling a small subgraph. We continue our previous work on the subject by proving some experimentally found claims. Our theoretical setting does not assume that the graph is generated from a SBM. The task is to find a SBM that is optimal for modeling the given graph in the sense of MDL. This assumption matches with real-life situations when no random generative model is appropriate. Our aim is to show that regular decomposition is a viable and robust method for large graphs emerging, say, in Big Data area.
  • Malkamäki, Arttu; Ylä-Anttila, Tuomas; Brockhaus, Maria; Toppinen, Anne; Wagner, Paul (2021)
    Competing coalitions can stabilise policymaking and hinder policy changes that are required to address the mounting pressures on land use systems across the globe. Thus, understanding the driving forces of coalition formation is important. This paper builds on the Advocacy Coalition Framework to determine the relative contributions of two sets of beliefs (more general policy core beliefs and more specific beliefs concerning policy instruments) to coalition formation in South African tree plantation politics and to identify coalitions therein. Discourse Network Analysis was used to code 656 statements regarding 40 beliefs to create network data from 55 interviews with organisational elites. Results from a network analysis of the twelve most salient beliefs indicate that dissimilar policy core beliefs about the validity of environmental regulation, social costs of tree plantations, and the conditionality of land reform in South Africa divide actors into two coalitions: the hegemonic “business-as-usual” coalition and the minority “justice and change” coalition. These boundaries were confirmed by comparing the network based on shared policy core beliefs with a co-ordination network. Dissimilar beliefs concerning policy instruments, including eco-certification and an indicative zoning, also divide actors, yet actors’ reasoning for or against these instruments differ to the degree that united fronts are unlikely to form. Hegemonic coalitions that combine selected state and business interests with labour arguments and prioritise short-term economic efficiency threaten to delay the necessary changes away from business-as-usual across land use systems in South Africa and beyond.