Are developers fixing their own bugs?: Tracing bug-fixing and bug-seeding committers

This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 IGI GlobalThe process of fixing software bugs plays a key role in the maintenance activities of a software project. Ideally, code ownership and responsibility should be enforced among developers working on the same artifacts, so that those introducing buggy code could also contribute to its fix. However, especially in FLOSS projects, this mechanism is not clearly understood: in particular, it is not known whether those contributors fixing a bug are the same introducing and seeding it in the first place. This paper analyzes the comm-central FLOSS project, which hosts part of the Thunderbird, SeaMonkey, Lightning extensions and Sunbird projects from the Mozilla community. The analysis is focused at the level of lines of code and it uses the information stored in the source code management system. The results of this study show that in 80% of the cases, the bug-fixing activity involves source code modified by at most two developers. It also emerges that the developers fixing the bug are only responsible for 3.5% of the previous modifications to the lines affected; this implies that the other developers making changes to those lines could have made that fix. In most of the cases the bug fixing process in comm-central is not carried out by the same developers than those who seeded the buggy code.This work has been partially funded by the European Commission, under the ALERT project (ICT-258098)

Information flow through a model of the C. elegans klinotaxis circuit

Understanding how information about external stimuli is transformed into behavior is one of the central goals of neuroscience. Here we characterize the information flow through a complete sensorimotor circuit: from stimulus, to sensory neurons, to interneurons, to motor neurons, to muscles, to motion. Specifically, we apply a recently developed framework for quantifying information flow to a previously published ensemble of models of salt klinotaxis in the nematode worm C. elegans. The models are grounded in the neuroanatomy and currently known neurophysiology of the worm. The unknown model parameters were optimized to reproduce the worm's behavior. Information flow analysis reveals several key principles underlying how the models operate: (1) Interneuron class AIY is responsible for integrating information about positive and negative changes in concentration, and exhibits a strong left/right information asymmetry. (2) Gap junctions play a crucial role in the transfer of information responsible for the information symmetry observed in interneuron class AIZ. (3) Neck motor neuron class SMB implements an information gating mechanism that underlies the circuit's state-dependent response. (4) The neck carries non-uniform distribution about changes in concentration. Thus, not all directions of movement are equally informative. Each of these findings corresponds to an experimental prediction that could be tested in the worm to greatly refine our understanding of the neural circuit underlying klinotaxis. Information flow analysis also allows us to explore how information flow relates to underlying electrophysiology. Despite large variations in the neural parameters of individual circuits, the overall information flow architecture circuit is remarkably consistent across the ensemble, suggesting that information flow analysis captures general principles of operation for the klinotaxis circuit

Estimating development effort in free/open source software projects by mining software repositories: A case study of OpenStack

Because of the distributed and collaborative nature of free/open source software (FOSS) projects, the development effort invested in a project is usually unknown, even after the software has been released. However, this information is becoming of major interest, especially-but not only-because of the growth in the number of companies for which FOSS has become relevant for their business strategy. In this paper we present a novel approach to estimate effort by considering data from source code management repositories. We apply our model to the OpenStack project, a FOSS project with more than 1,000 authors, in which several tens of companies cooperate. Based on data from its repositories and together with the input from a survey answered by more than 100 developers, we show that the model offers a simple, but sound way of obtaining software development estimations with bounded margins of error.Gregorio Robles, Carlos Cervig on and Jes us M. Gonz alez-Barahona, project SobreSale (TIN2011-28110). and The work of Daniel Izquierdo has been funded in part by the Torres Quevedo program (PTQ-12-05577

New models for two real scalar fields and their kinklike solutions

In this work we study the presence of kinks in models described by two real scalar fields in bi-dimensional space-time. We generate new two-field models, constructed from distinct but important one-field models, and we solve them with techniques that we introduce in the current work. We illustrate the results with several examples of current interest to high energy physics.Comment: 8 pages, 6 figures; To appear in Adv. High Energy Phy

User requirements for multimedia indexing and retrieval of unedited audio-visual footage - RUSHES

Multimedia analysis and reuse of raw un-edited audio visual content known as rushes is gaining acceptance by a large number of research labs and companies. A set of research projects are considering multimedia indexing, annotation, search and retrieval in the context of European funded research, but only the FP6 project RUSHES is focusing on automatic semantic annotation, indexing and retrieval of raw and un-edited audio-visual content. Even professional content creators and providers as well as home-users are dealing with this type of content and therefore novel technologies for semantic search and retrieval are required. As a first result of this project, the user requirements and possible user-scenarios are presented in this paper. These results lay down the foundation for the research and development of a multimedia search engine particularly dedicated to the specific needs of the users and the content

On domain walls in a Ginzburg-Landau non-linear S^2-sigma model

The domain wall solutions of a Ginzburg-Landau non-linear $S^2$-sigma hybrid model are unveiled. There are three types of basic topological walls and two types of degenerate families of composite - one topological, the other non-topological- walls. The domain wall solutions are identified as the finite action trajectories (in infinite time) of a related mechanical system that is Hamilton-Jacobi separable in sphero-conical coordinates. The physical and mathematical features of these domain walls are thoroughly discussed.Comment: 26 pages, 18 figure

The use of the Gompertz model in its differential form for weed emergence modelling

Los modelos empíricos que se utilizan para describir y predecir las emergencias de las malas hierbas basados en temperatura y humedad del suelo presentan dos puntos débiles: la ambigüedad que supone tomar como instante inicial de acumulación de grados termales o hidrotermales el día del laboreo y la necesidad de su validación posterior. La utilización de estos modelos en su forma diferencial haría innecesario establecer un día concreto de inicio de la acumulación de grados y podría aportar predicciones sin necesidad de validaciones. Para comprobar estas hipótesis, la ecuación de Gompertz, uno de los modelos más utilizados para describir emergencias, se ha aplicado en su forma diferencial a 35 conjuntos de datos de malas hierbas de diferentes localidades. El ajuste obtenido reproduce de forma satisfactoria la dinámica de emergencias observada en el campo y permite determinar con precisión el momento de aplicación de una medida de control.The Gompertz model, in its differential form, is used for weed emergence modelling. Empirical models that are used to describe the emergence patterns of weeds based on temperature and soil moisture have two weaknesses: the uncertainty of when to start counting and the need for validation. The use of these models in their differential form avoids setting up an ambiguous starting date and also avoids model validation. In order to check these hypotheses, the Gompertz equation, one of the models used most frequently for weed emergence, was verified in 35 data sets of weed species emergence from different areas within the Iberian Peninsula. In all cases, the emergence pattern and forecast for ideal weed control timing was sufficiently accurate

Optimal Technology Selection and Operation of Bio-methane CHP Units for Commercial Buildings

This paper explores the optimal implementation of bio-methane fuelled combined heat and power (CHP) systems to satisfy heat and electricity demands of commercial buildings; with the overarching goal of making cost-effective investments and decarbonizing building operations. The research work consisted in the development of a CHP technology selection and operation (TSO) optimization model. Its results can be utilized to develop a strategy for investment in bio-methane CHP projects for a portfolio of buildings. The TSO model enables a new approach for the selection and operation of CHP units that encompasses whole life costing, carbon emissions as well as real-time energy prices and demands, providing a more comprehensive result than current methods. Utilizing historic metered energy demands, projected energy prices and a portfolio of available CHP technologies, the mathematical model simultaneously solves for an optimal CHP unit selection and operational strategy for a determined building based on a preferred objective: minimizing cost, minimizing GHG emissions, or a mix of both. Results of this model prove that attractive cost and emissions savings are possible through the optimal selection and operation of CHP technologies fuelled by bio-methan