Convex Cycle Bases

Convex cycles play a role e.g. in the context of product graphs. We introduce convex cycle bases and describe a polynomial-time algorithm that recognizes whether a given graph has a convex cycle basis and provides an explicit construction in the positive case. Relations between convex cycles bases and other types of cycles bases are discussed. In particular we show that if G has a unique minimal cycle bases, this basis is convex. Furthermore, we characterize a class of graphs with convex cycles bases that includes partial cubes and hence median graphs. (authors' abstract)Series: Research Report Series / Department of Statistics and Mathematic

Tuning the Performance of a Computational Persistent Homology Package

In recent years, persistent homology has become an attractive method for data analysis. It captures topological features, such as connected components, holes, and voids from point cloud data and summarizes the way in which these features appear and disappear in a filtration sequence. In this project, we focus on improving the performanceof Eirene, a computational package for persistent homology. Eirene is a 5000-line open-source software library implemented in the dynamic programming language Julia. We use the Julia profiling tools to identify performance bottlenecks and develop novel methods to manage them, including the parallelization of some time-consuming functions on multicore/manycore hardware. Empirical results show that performance can be greatly improved

Integral cycle bases for cyclic timetabling

AbstractCyclic railway timetables are typically modeled by a constraint graph G with a cycle period time T, in which a periodic tension x in G corresponds to a cyclic timetable. In this model, the periodic character of the tension x is guaranteed by requiring periodicity for each cycle in a strictly fundamental cycle basis, that is, the set of cycles generated by the chords of a spanning tree of G.We introduce the more general concept of integral cycle bases for characterizing periodic tensions. We characterize integral cycle bases using the determinant of a cycle basis, and investigate further properties of integral cycle bases.The periodicity of a single cycle is modeled by a so-called cycle integer variable. We exploit the wider class of integral cycle bases to find tighter bounds for these cycle integer variables, and provide various examples with tighter bounds. For cyclic railway timetabling in particular, we consider Minimum Cycle Bases for constructing integral cycle bases with tight bounds

Learning From Experience With Performance Assessment Frameworks for General Budget Support

This report provides the findings of a study financed by SECO and undertaken under the auspices of the OECD-DAC multi-country evaluation of General Budget Support (GBS). The overall objective was to gather preliminary lessons on what could be good international practice in the development\ud of Performance Assessment Frameworks (PAFs) for GBS. The study is based on the experience of three countries which have adopted harmonised PAFs – namely Ghana, Mozambique, and Tanzania, and two which are moving in this direction – Benin and Nicaragua. In order to assess the effectiveness of these PAFs, the study employed a simplified, standard framework reflecting the OECD-DAC guiding principles for the provision of budget support.\u

THE CHANGING NATURE OF RURAL COMMUNITIES

Community/Rural/Urban Development,