2,591 research outputs found
KADABRA is an ADaptive Algorithm for Betweenness via Random Approximation
We present KADABRA, a new algorithm to approximate betweenness centrality in
directed and undirected graphs, which significantly outperforms all previous
approaches on real-world complex networks. The efficiency of the new algorithm
relies on two new theoretical contributions, of independent interest. The first
contribution focuses on sampling shortest paths, a subroutine used by most
algorithms that approximate betweenness centrality. We show that, on realistic
random graph models, we can perform this task in time
with high probability, obtaining a significant speedup with respect to the
worst-case performance. We experimentally show that this new
technique achieves similar speedups on real-world complex networks, as well.
The second contribution is a new rigorous application of the adaptive sampling
technique. This approach decreases the total number of shortest paths that need
to be sampled to compute all betweenness centralities with a given absolute
error, and it also handles more general problems, such as computing the
most central nodes. Furthermore, our analysis is general, and it might be
extended to other settings.Comment: Some typos correcte
Improving the Parallel Execution of Behavior Trees
Behavior Trees (BTs) have become a popular framework for designing
controllers of autonomous agents in the computer game and in the robotics
industry. One of the key advantages of BTs lies in their modularity, where
independent modules can be composed to create more complex ones. In the
classical formulation of BTs, modules can be composed using one of the three
operators: Sequence, Fallback, and Parallel. The Parallel operator is rarely
used despite its strong potential against other control architectures as Finite
State Machines. This is due to the fact that concurrent actions may lead to
unexpected problems similar to the ones experienced in concurrent programming.
In this paper, we introduce Concurrent BTs (CBTs) as a generalization of BTs in
which we introduce the notions of progress and resource usage. We show how CBTs
allow safe concurrent executions of actions and we analyze the approach from a
mathematical standpoint. To illustrate the use of CBTs, we provide a set of use
cases in robotics scenarios
On the Implementation of Behavior Trees in Robotics
There is a growing interest in Behavior Trees (BTs) as a tool to describe and
implement robot behaviors. BTs were devised in the video game industry and
their adoption in robotics resulted in the development of ad-hoc libraries to
design and execute BTs that fit complex robotics software architectures.
While there is broad consensus on how BTs work, some characteristics rely on
the implementation choices done in the specific software library used.
In this letter, we outline practical aspects in the adoption of BTs and the
solutions devised by the robotics community to fully exploit the advantages of
BTs in real robots. We also overview the solutions proposed in open-source
libraries used in robotics, we show how BTs fit in robotic software
architecture, and we present a use case example
High resolution map of migrants in the EU
This report describes a data set generated from the harmonization and spatial processing of official census statistics collected from National Statistical Institutes in 8 EU Member States (France, Germany, Ireland, Italy, Netherlands, Portugal, Spain and UK).
The dataset provides a map at high spatial resolution of the population with migrant background in these Member States.
The uniqueness of the data set resides both the high level of spatial resolution (cells of 100 by 100 m) and the large geographical coverage which is including almost 45 thousand local administrative units.
From this data set it is possible to calculate indicators of concentration of migrants, diversity and spatial residential segregation which can support comparative research and policies on the local aspect of the integration of migrants in the EU.JRC.E.6-Demography, Migration and Governanc
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