7,523 research outputs found
Robustness analysis of evolutionary controller tuning using real systems
A genetic algorithm (GA) presents an excellent method for controller parameter tuning. In our work, we evolved the heading as well as the altitude controller for a small lightweight helicopter. We use the real flying robot to evaluate the GA's individuals rather than an artificially consistent simulator. By doing so we avoid the ldquoreality gaprdquo, taking the controller from the simulator to the real world. In this paper we analyze the evolutionary aspects of this technique and discuss the issues that need to be considered for it to perform well and result in robust controllers
Simulation from endpoint-conditioned, continuous-time Markov chains on a finite state space, with applications to molecular evolution
Analyses of serially-sampled data often begin with the assumption that the
observations represent discrete samples from a latent continuous-time
stochastic process. The continuous-time Markov chain (CTMC) is one such
generative model whose popularity extends to a variety of disciplines ranging
from computational finance to human genetics and genomics. A common theme among
these diverse applications is the need to simulate sample paths of a CTMC
conditional on realized data that is discretely observed. Here we present a
general solution to this sampling problem when the CTMC is defined on a
discrete and finite state space. Specifically, we consider the generation of
sample paths, including intermediate states and times of transition, from a
CTMC whose beginning and ending states are known across a time interval of
length . We first unify the literature through a discussion of the three
predominant approaches: (1) modified rejection sampling, (2) direct sampling,
and (3) uniformization. We then give analytical results for the complexity and
efficiency of each method in terms of the instantaneous transition rate matrix
of the CTMC, its beginning and ending states, and the length of sampling
time . In doing so, we show that no method dominates the others across all
model specifications, and we give explicit proof of which method prevails for
any given and endpoints. Finally, we introduce and compare three
applications of CTMCs to demonstrate the pitfalls of choosing an inefficient
sampler.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS247 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
12th International Workshop on Termination (WST 2012) : WST 2012, February 19–23, 2012, Obergurgl, Austria / ed. by Georg Moser
This volume contains the proceedings of the 12th International Workshop on Termination (WST 2012), to be held February 19–23, 2012 in Obergurgl, Austria. The goal of the Workshop on Termination is to be a venue for presentation and discussion of all topics in and around termination. In this way, the workshop tries to bridge the gaps between different communities interested and active in research in and around termination. The 12th International Workshop on Termination in Obergurgl continues the successful workshops held in St. Andrews (1993), La Bresse (1995), Ede (1997), Dagstuhl (1999), Utrecht (2001), Valencia (2003), Aachen (2004), Seattle (2006), Paris (2007), Leipzig (2009), and Edinburgh (2010). The 12th International Workshop on Termination did welcome contributions on all aspects of termination and complexity analysis. Contributions from the imperative, constraint, functional, and logic programming communities, and papers investigating applications of complexity or termination (for example in program transformation or theorem proving) were particularly welcome. We did receive 18 submissions which all were accepted. Each paper was assigned two reviewers. In addition to these 18 contributed talks, WST 2012, hosts three invited talks by Alexander Krauss, Martin Hofmann, and Fausto Spoto
FCMpy: A Python Module for Constructing and Analyzing Fuzzy Cognitive Maps
FCMpy is an open source package in Python for building and analyzing Fuzzy
Cognitive Maps. More specifically, the package allows 1) deriving fuzzy causal
weights from qualitative data, 2) simulating the system behavior, 3) applying
machine learning algorithms (e.g., Nonlinear Hebbian Learning, Active Hebbian
Learning, Genetic Algorithms and Deterministic Learning) to adjust the FCM
causal weight matrix and to solve classification problems, and 4) implementing
scenario analysis by simulating hypothetical interventions (i.e., analyzing
what-if scenarios).Comment: 22 pages, 9 Figure
A review of estimation of distribution algorithms in bioinformatics
Evolutionary search algorithms have become an essential asset in the algorithmic toolbox for solving high-dimensional optimization problems in across a broad range of bioinformatics problems. Genetic algorithms, the most well-known and representative evolutionary search technique, have been the subject of the major part of such applications. Estimation of distribution algorithms (EDAs) offer a novel evolutionary paradigm that constitutes a natural and attractive alternative to genetic algorithms. They make use of a probabilistic model, learnt from the promising solutions, to guide the search process. In this paper, we set out a basic taxonomy of EDA techniques, underlining the nature and complexity of the probabilistic model of each EDA variant. We review a set of innovative works that make use of EDA techniques to solve challenging bioinformatics problems, emphasizing the EDA paradigm's potential for further research in this domain
Parsimonious Inference of Hybridization in the Presence of Incomplete Lineage Sorting
Hybridization plays an important evolutionary role in several groups of organisms.
A phylogenetic approach to detect hybridization entails sequencing multiple loci
across the genomes of a group of species of interest, reconstructing their gene trees,
and taking their differences as indicators of hybridization. However, methods that
follow this approach mostly ignore population effects, such as incomplete lineage
sorting (ILS). Given that hybridization occurs between closely related organisms, ILS
may very well be at play and, hence, must be accounted for in the analysis
framework. To address this issue, we present a parsimony criterion for reconciling
gene trees within the branches of a phylogenetic network, and a local search heuristic
for inferring phylogenetic networks from collections of gene-tree topologies under this
criterion. This framework enables phylogenetic analyses while accounting for both
hybridization and ILS. Further, we propose two techniques for incorporating
information about uncertainty in gene-tree estimates. Our simulation studies
demonstrate the good performance of our framework in terms of identifying the
location of hybridization events, as well as estimating the proportions of genes that
underwent hybridization. Also, our framework shows good performance in terms of
efficiency on handling large data sets in our experiments. Further, in analyzing a
yeast data set, we demonstrate issues that arise when analyzing real data sets. While
a probabilistic approach was recently introduced for this problem, and while
parsimonious reconciliations have accuracy issues under certain settings, our
parsimony framework provides a much more computationally efficient technique for
this type of analysis. Our framework now allows for genome-wide scans for
hybridization, while also accounting for ILS
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