Fast parallel $$\alpha $$-stable distribution function evaluation and parameter estimation using OpenCL in GPGPUs

\(\alpha \)-Stable distributions are a family of probability distributions found to be suitable to model many complex processes and phenomena in several research fields, such as medicine, physics, finance and networking, among others. However, the lack of closed expressions makes their evaluation analytically intractable, and alternative approaches are computationally expensive. Existing numerical programs are not fast enough for certain applications and do not make use of the parallel power of general purpose graphic processing units. In this paper, we develop novel parallel algorithms for the probability density function and cumulative distribution function—including a parallel Gauss–Kronrod quadrature—, quantile function, random number generator and maximum likelihood estimation of \(\alpha \)-stable distributions using OpenCL, achieving significant speedups and precision in all cases. Thanks to the use of OpenCL, we also evaluate the results of our library with different GPU architectures.     

Technology for social housing in Latin America : An evaluation of the CYTED research and development programme

Since the mid 1980s an international programme of scientific and technological co-operation between Spain, Portugal and Latin America has been underway (CYTED). One of the 16 sub-programmes is focussing on Technology for Social Housing, and has brought together hundreds of researchers and housing activists from every corner of the continent, to seek pragmatic approaches to improve the housing conditions of the poor majority in Latin America. In addition to cataloguing and exchanging existing experiences, a wide-ranging and detailed programme of research and development of innovative housing technologies has been set in motion. These include materials, techniques and processes.The paper briefly outlines the characteristics of the existing housing situation in Latin America in order to identify the main elements upon which these new approaches are built. The key components of the CYTED housing programme are then described and illustrated using examples of different projects. A common theme is the relationship between the building process and social patterns, particularly the potential for cooperation and community self-help construction. The paper then identifies some limitations of the programme and concludes that despite the commitment and creativity of those involved, the effectiveness of many projects and the general validity of the approaches adopted, severe structural constraints are likely to limit the impact of the programme. However the increased contacts, communication and opportunities for collaboration within the continent provide grounds for limited optimism about future developments.     

Working precarious careers trajectories: tracing neoliberal discourses in younger workers’ narratives

ABSTRACT

The aim of this article is to explore how, in the context of the post Global Financial Crisis (GFC), some Italian younger workers in a specific geographical region in Italy recount their work trajectories. Drawing on narrative interviews with ten participants (aged between 24 and 30) as part of a research project carried out in the Autonomous region of Aosta Valley in Italy, the article traces discourses closely associated with neoliberalism – the discourses of the entrepreneurial self, employability and self-responsibilisation – through which subjects’ work experiences take shape. Moreover, the analysis highlights how locality, one’s personal relation with the geographical territory, makes more complex the younger people’s negotiations in crafting themselves vis-à-vis precarious employment opportunities and wider socio-economic dynamics in respect of precarious employment opportunities.     

Resistance to metropolitan institutionality and planning in Chile

In this article, the authors review and analyse two key processes conducted by the Chilean state over the past 50 years. The first process consists of the development of specific planning instruments for the particular realities of metropolitan areas. The second process consists of the successive legislative attempts to work towards a definition of a new form of institutionality for cities with metropolitan profiles. These attempts have either failed or solely become bills of law. Both processes suggest a political and technical resistance throughout history, to substantially modify institutionality, as well as planning instruments, in order to make them more appropriate and consistent with the needs of growing metropolitan areas in Chile.     

Parameter estimation for fractional birth and fractional death processes

The fractional birth and the fractional death processes are more desirable in practice than their classical counterparts as they naturally provide greater flexibility in modeling growing and decreasing systems. In this paper, we propose formal parameter estimation procedures for the fractional Yule, the fractional linear death, and the fractional sublinear death processes. The methods use all available data possible, are computationally simple and asymptotically unbiased. The procedures exploited the natural structure of the random inter-birth and inter-death times that are known to be independent but are not identically distributed. We also showed how these methods can be applied to certain models with more general birth and death rates. The computational tests showed favorable results for our proposed methods even with relatively small sample sizes. The proposed methods are also illustrated using the branching times of the plethodontid salamanders data of (Syst. Zool. 28:579–599, 1979).     

Discussion on the paper “On simulation and properties of the stable law” by L. Devroye and L. James

We congratulate the authors for the interesting paper. The reading has been really pleasant and instructive. We discuss briefly only some of the interesting results given in Devroye and James (Stat Methods Appl 2014) with particular attention to evolution problems. The contribution of the results collected in the paper is useful in a more wide class of applications in many areas of applied mathematics.     

Improving an exact approach for solving separable integer quadratic knapsack problems

We consider the specially structured (pure) integer Quadratic Multi-Knapsack Problem (QMKP) tackled in the paper “Exact solution methods to solve large scale integer quadratic knapsack problems” by D. Quadri, E. Soutif and P. Tolla (2009), recently appeared on this journal, where the problem is solved by transforming it into an equivalent 0–1 linearized Multi-Knapsack Problem (MKP). We show that, by taking advantage of the structure of the transformed (MKP), it is possible to derive an effective variable fixing procedure leading to an improved branch-and-bound approach. This procedure reduces dramatically the resulting linear problem size inducing an impressive improvement in the performances of the related branch and bound approach when compared to the results of the approach proposed by D. Quadri, E. Soutif and P. Tolla.     

Improving innovation performance through environmental practices in the fashion industry: the moderating effect of internationalisation and the influence of collaboration

In recent years, the scientific literature on supply chain management has increasingly debated on environmental sustainability as well as collaboration, presenting these issues as an important source of innovation along the supply chain. By combining literature streams on environmental sustainability, supply chain collaboration and innovation at the supply chain level, this paper aims to analyse whether the adoption of environmental sustainability practices and collaboration along the supply chain implies better innovation performance, in terms of differentiation from the competitors for higher quality, product or process. The paper also investigates whether the internationalisation, in terms of both production and distribution activities, negatively moderates this relationship. The study focuses on the fashion industry, and a survey of major Italian fashion companies was conducted. The main results of the research clearly show the positive impact of these practices on innovation performance. The paper also proves the existence of a moderating effect exerted by internationalisation on the relationship between environmental sustainability and innovation performance.