OpenCL Actors - Adding Data Parallelism to Actor-based Programming with CAF

The actor model of computation has been designed for a seamless support of concurrency and distribution. However, it remains unspecific about data parallel program flows, while available processing power of modern many core hardware such as graphics processing units (GPUs) or coprocessors increases the relevance of data parallelism for general-purpose computation. In this work, we introduce OpenCL-enabled actors to the C++ Actor Framework (CAF). This offers a high level interface for accessing any OpenCL device without leaving the actor paradigm. The new type of actor is integrated into the runtime environment of CAF and gives rise to transparent message passing in distributed systems on heterogeneous hardware. Following the actor logic in CAF, OpenCL kernels can be composed while encapsulated in C++ actors, hence operate in a multi-stage fashion on data resident at the GPU. Developers are thus enabled to build complex data parallel programs from primitives without leaving the actor paradigm, nor sacrificing performance. Our evaluations on commodity GPUs, an Nvidia TESLA, and an Intel PHI reveal the expected linear scaling behavior when offloading larger workloads. For sub-second duties, the efficiency of offloading was found to largely differ between devices. Moreover, our findings indicate a negligible overhead over programming with the native OpenCL API.Comment: 28 page

Equality of averaged and quenched large deviations for random walks in random environments in dimensions four and higher

We consider large deviations for nearest-neighbor random walk in a uniformly elliptic i.i.d. environment. It is easy to see that the quenched and the averaged rate functions are not identically equal. When the dimension is at least four and Sznitman's transience condition (T) is satisfied, we prove that these rate functions are finite and equal on a closed set whose interior contains every nonzero velocity at which the rate functions vanish.Comment: 17 pages. Minor revision. In particular, note the change in the title of the paper. To appear in Probability Theory and Related Fields

Socio-economic and Demographic factors associated with injecting drug use among drug users in Karachi, Pakistan

Objective: To identify the socio-economic and demographic factors associated with injecting drug users (IDUs) in Karachi. Methods: We recruited 242 IDUs (taking drugs through sub-dermal routes) and 231 non-IDUs (taking drugs other than sub-dermal routes) from February through June 1996. IDUs were interviewed regarding sociodemographic factors, economic condition, and social network (marital status, living with spouse). In addition, information regarding location of drug users within the city (districts of Karachi) and current history of sexually transmitted diseases (STDs) were gathered. Moreover, blood samples were also obtained for HIV testing .Results: Multivariate analysis showed that the income generation via illegal modes [AOR 1.6, 95% CI 1.0-2.6], non-sharing of income with family [AOR 1.7, 95% CI 1.1-2.7] and presence of suicidal thoughts [AOR 2.0, 95% CI 1.1-3.8] were associated with the use of drugs through injections. Further, drug users from districts West, East and Central were more likely to use drug through injection as compared to drug users from district South. The history of genital herpes was also found to be associated with injecting drug use. One IDU was found seropositive for HIV. Conclusion: The high-risk behaviors, such as illegal modes of earning and presence of suicidal thoughts, among IDUs suggest that the group needs rehabilitation programme. Moreover, non-sharing of income suggest that IDUs are isolated from social network, therefore primary prevention activities with focus on improving socioeconomic conditions and social networking can reduce drug use through injections. Focused interventions on target districts would be helpful in reducing IDU (JPMA 53:511;2003)

The importance of socio-economic context for social marketing models for improving reproductive health: Evidence from 555 years of program experience

BACKGROUND: Over the past two decades, social marketing programs have become an important element of the national family planning and HIV prevention strategy in several developing countries. As yet, there has not been any comprehensive empirical assessment to determine which of several social marketing models is most effective for a given socio-economic context. Such an assessment is urgently needed to inform the design of future social marketing programs, and to avoid that programs are designed using an ineffective model. METHODS: This study addresses this issue using a database of annual statistics about reproductive health oriented social marketing programs in over 70 countries. In total, the database covers 555 years of program experience with social marketing programs that distribute and promote the use of oral contraceptives and condoms. Specifically, our analysis assesses to what extent the model used by different reproductive health social marketing programs has varied across different socio-economic contexts. We then use random effects regression to test in which socio-economic context each of the models is most successful at increasing use of socially marketed oral contraceptives and condoms. RESULTS: The results show that there has been a tendency to design reproductive health social marketing program with a management structure that matches the local context. However, the evidence also shows that this has not always been the case. While socio-economic context clearly influences the effectiveness of some of the social marketing models, program maturity and the size of the target population appear equally important. CONCLUSIONS: To maximize the effectiveness of future social marketing programs, it is essential that more effort is devoted to ensuring that such programs are designed using the model or approach that is most suitable for the local context

HIGH-CYCLE FATIGUE BEHAVIOUR OF SPHEROIDAL GRAPHITE CAST IRON

International audienc

A Silicon-Based Monolithic Optical Frequency Comb Source

Recently developed techniques for generating precisely equidistant optical frequencies over broad wavelength ranges are revolutionizing precision physical measurement [1-3]. These frequency "combs" are produced primarily using relatively large, ultrafast laser systems. However, recent research has shown that broad-bandwidth combs can be produced using highly-nonlinear interactions in microresonator optical parametric oscillators [4-11]. Such devices not only offer the potential for developing extremely compact optical atomic clocks but are also promising for astronomical spectroscopy [12-14], ultrashort pulse shaping [15], and ultrahigh-speed communications systems. Here we demonstrate the generation of broad-bandwidth optical frequency combs from a CMOS-compatible integrated microresonator [16,17], which is a fully-monolithic and sealed chip-scale device making it insensitive to the surrounding environment. We characterize the comb quality using a novel self-referencing method and verify that the comb line frequencies are equidistant over a bandwidth that is nearly an order of magnitude larger than previous measurements. In addition, we investigate the ultrafast temporal properties of the comb and demonstrate its potential to serve as a chip-scale source of ultrafast (sub-ps) pulses

Cut Points and Diffusions in Random Environment

In this article we investigate the asymptotic behavior of a new class of multi-dimensional diffusions in random environment. We introduce cut times in the spirit of the work done by Bolthausen, Sznitman and Zeitouni, see [4], in the discrete setting providing a decoupling effect in the process. This allows us to take advantage of an ergodic structure to derive a strong law of large numbers with possibly vanishing limiting velocity and a central limit theorem under the quenched measure.Comment: 44 pages; accepted for publication in "Journal of Theoretical Probability