Performance scalability analysis of JavaScript applications with web workers

Web applications are getting closer to the performance of native applications taking advantage of new standard–based technologies. The recent HTML5 standard includes, among others, the Web Workers API that allows executing JavaScript applications on multiple threads, or workers. However, the internals of the browser’s JavaScript virtual machine does not expose direct relation between workers and running threads in the browser and the utilization of logical cores in the processor. As a result, developers do not know how performance actually scales on different environments and therefore what is the optimal number of workers on parallel JavaScript codes. This paper presents the first performance scalability analysis of parallel web apps with multiple workers. We focus on two case studies representative of different worker execution models. Our analyses show performance scaling on different parallel processor microarchitectures and on three major web browsers in the market. Besides, we study the impact of co–running applications on the web app performance. The results provide insights for future approaches to automatically find out the optimal number of workers that provide the best tradeoff between performance and resource usage to preserve system responsiveness and user experience, especially on environments with unexpected changes on system workload.Peer ReviewedPostprint (author's final draft

Speculative dynamic vectorization

Traditional vector architectures have shown to be very effective for regular codes where the compiler can detect data-level parallelism. However, this SIMD parallelism is also present in irregular or pointer-rich codes, for which the compiler is quite limited to discover it. In this paper we propose a microarchitecture extension in order to exploit SIMD parallelism in a speculative way. The idea is to predict when certain operations are likely to be vectorizable, based on some previous history information. In this case, these scalar instructions are executed in a vector mode. These vector instructions operate on several elements (vector operands) that are anticipated to be their input operands and produce a number of outputs that are stored on a vector register in order to be used by further instructions. Verification of the correctness of the applied vectorization eventually changes the status of a given vector element from speculative to non-speculative, or alternatively, generates a recovery action in case of misspeculation. The proposed microarchitecture extension applied to a 4-way issue superscalar processor with one wide bus is 19% faster than the,same processor with 4 scalar buses to Ll data cache. This speed up is due basically to 1) the reduction in number of memory accesses, 15% for SpecInt and 20% for SpecFP, 2) the transformation of scalar arithmetic instructions into their vector counterpart, 28% for SpecInt and 23% for SpecFP, and 3) the exploitation of control independence for mispredicted branches.Peer ReviewedPostprint (published version

Production of 1,3-propanediol by Clostridium butyricum VPI 3266 using a synthetic medium and raw glycerol

Growth inhibition of Clostridium butyricum VPI 3266 by raw glycerol, obtained from the biodiesel production process, was evaluated. C. butyricum presents the same tolerance to raw and to commercial glycerol, when both are of similar grade, i.e. above 87% (w/v). A 39% increase of growth inhibition was observed in the presence of 100 g l 1 of a lower grade raw glycerol (65% w/v). Furthermore, 1,3-propanediol production from two raw glycerol types (65% w/v and 92% w/v), without any prior purification, was observed in batch and continuous cultures, on a synthetic medium. No significant differences were found in C. butyricum fermentation patterns on raw and commercial glycerol as the sole carbon source. In every case, 1,3-propanediol yield was around 0.60 mol/mol glycerol consumed

Production of 1,3-Propanediol by Clostridium butyricum VPI 3266 in continuous cultures with high yield and productivity

The effects of dilution rate and substrate feed concentration on continuous glycerol fermentation by Clostridium butyricum VPI 3266, a natural 1,3-propanediol producer, were evaluated in this work. A high and constant 1,3-propanediol yield (around 0.65 mol/mol), close to the theoretical value, was obtained irrespective of substrate feed concentration or dilution rate. Improvement of 1,3-propanediol volumetric productivity was achieved by increasing the dilution rate, at a fixed feed substrate concentration of 30, 60 or 70 g l-1. Higher 1,3-propanediol final concentrations and volumetric productivities were also obtained when glycerol feed concentration was increased from 30 to 60 g l-1, at D=0.05–0.3 h-1, and from 60–70 g l-1, at D=0.05 and 0.1 h-1. 30 g l-1 of 1,3-propanediol and the highest reported value of productivity, 10.3 g l-1 h-1, was achieved at D=0.30 h-1 and 60 g l-1 of feed glycerol. A switch to an acetate/butyrate ratio higher than one was observed for 60 g l-1 of feed glycerol and a dilution rate higher than 0.10 h-1; moreover, at D=0.30 h-1 3-hydroxypropionaldehyde accumulation was observed for the first time in the fermentation broth of C. butyricum

A neuroimaging study of pleasant and unpleasant olfactory perceptions of virgin olive oil

Functional magnetic resonance imaging (fMRI) has been used to collect information from neurons that receive direct input from olfactory bulbs when subjects smell virgin olive oil. The pleasant aroma of three extra virgin olive oils (var. Royal, Arbequina and Picual) and three virgin olive oils with sensory defects (rancid, fusty and winey/vinegary) were presented to 14 subjects while a fMRI scan acquired data from the brain activity. Data were subjected to a two-sample t test analysis, which allows a better interpretation of results particularly when data are studied across different subjects. Most of the activations, which were located in the frontal lobe, are related to the olfactory task regardless of the hedonic component of perception (e.g. Brodmann areas 10, 11). Comparing the samples with pleasant and unpleasant aromas, differences were found at the anterior cingu�late gyrus (Brodmann area 32), at the temporal lobe (Brodmann area 38), and inferior frontal gyrus (Brodmann area 47), while intense aromas activated Brodmann area 6. The actual perceptions described by the subjects and the concentration of the odorant compounds in the samples were considered in the interpretation of the results.Estudio mediante neuroimagen de percepciones olfativas agradables y desagradables de aceites de oliva virgen. La imagen por resonancia magnética funcional (fMRI) ha sido empleada para estudiar la información de la respuesta cerebral producida al estimular las neuronas que participan en el proceso olfatorio tras percibir el aroma del aceite de oliva virgen (AOV). Se utilizó fMRI para la adquisición de los datos de la actividad cerebral de 14 sujetos a los que se presentaron tres aceites de oliva vírgenes de aroma agradable (var. Royal, Arbequina and Picual) y tres aceites de oliva vírgenes con defectos sensoriales (rancio, atrojado, avinado/avinagrado). Los datos se sometieron a una prueba t para observar diferencias entre dos grupos, la cual permite una mejor interpretación de los resultados, particularmente cuando los datos se estudian a través de diferentes sujetos. La mayoría de las activaciones, que se localizaron en lóbulos frontales, se relacionaron con la tarea olfatoria independientemente de la componente hedónica de la percepción (por ejemplo, áreas Brodmann 10, 11). Al comparar las muestras con aromas agradables y desagradables, se encontraron diferencias significativas en el giro cingulado anterior (área Brodmann 32), el lóbulo temporal (área Brodmann 38) y el giro frontal inferior (área Brodmann 47), mientras que los aromas más intensos activaron el área Brodmann 6. En la interpretación de los resultados se tuvo en cuenta tanto la percepción descrita por los sujetos como las concentraciones de los compuestos volátiles en las muestras.Ramón y Cajal Program AGL2008-01411, AGL2011- 30371-C02-01/02

Tracking Sensory Characteristics of Virgin Olive Oils During Storage: Interpretation of Their Changes from a Multiparametric Perspective

Virgin olive oil is inevitably subject to an oxidation process during storage that can affect its stability and quality due to off-flavors that develop before the oil surpasses its ‘best before’ date. Many parameters are involved in the oxidation process at moderate conditions. Therefore, a multiparametric study is necessary to establish a link between physico-chemical changes and sensory quality degradation in a real storage experiment. In this context, a storage experiment of 27 months was performed for four monovarietal virgin olive oils, bottled in transparent 500-mL PET bottles and subjected to conditions close to a supermarket scenario. Volatile composition, quality parameters and phenolic compounds were determined monthly. Simultaneously, an accredited sensory panel assessed their sensory characteristics. The stability of the fresh samples was also studied with the oxidative stability index (OSI) and mesh cell-FTIR. (E)-2-hexenal, (Z)-3-hexen-1-ol and (E)-2-hexen-1-ol were identified as markers of the fruity attribute. Hexanal and nonanal were also identified as compounds that were associated with the rise of median of defect during storage. Some disagreements were observed between the sensory assessment and the OSI analyzed by Rancimat. However, the increase of concentration of rancid markers agreed with the increase of aldehyde band measured with mesh cell-FTIR.Spanish Research State Agency (research projects AGL2015-69320-R and RTI2018-101546-B-C21

Mapa conceptual global como herramienta para la visión de conjunto de un sistema operativo

Numerosas asignaturas están formadas por un temario que está totalmente interrelacionado. Al final del curso los estudiantes deberían haber adquirido los conocimientos de cada tema pero, más importante aún, deberían saber cómo interactúan los diferentes temas entre ellos para obtener una visión global de la asignatura. Sin embargo, a menudo los estudiantes se centran en los temas por separado, en parte porque no les ofrecemos herramientas que les ayuden a relacionar las distintas partes del curso. En este trabajo presentamos el uso de un Mapa Conceptual Global (MCG) de una asignatura como recurso docente que ayuda al estudiante a obtener una visión de conjunto de todo el temario. La experiencia ha sido realizada como complemento de una clase de aprendizaje activo en una asignatura de Sistemas Operativos, pero pensamos que puede ser fácilmente aplicable a otros cursos.Peer Reviewe

Lowering costs of microbial cellulose

We have been conducting research with Acetobacter xylinium for microbial conversion of sugars to cellulose. A rotating disk biological contactor should lower costs considerably because its production rates are greater than for the usual method of surface culture. Another major cost saving comes from replacing expensive sugars in the medium with sugars derived from wastes. Extracts of spent grapes from wastes of Portuguese wine factories supply suitable sugars for good production of microbial cellulose

Dynamic web worker pool management for highly parallel javascript web applications

JavaScript web applications are improving performance mainly thanks to the inclusion of new standards by HTML5. Among others, web workers API allows multithreaded JavaScript web apps to exploit parallel processors. However, developers have difficulties to determine the minimum number of web workers that provide the highest performance. But even if developers found out this optimal number, it is a static value configured at the beginning of the execution. Because users tend to execute other applications in background, the estimated number of web workers could be non-optimal, because it may overload or underutilize the system. In this paper, we propose a solution for highly parallel web apps to dynamically adapt the number of running web workers to the actual available resources, avoiding the hassle to estimate a static optimal number of threads. The solution consists in the inclusion of a web worker pool and a simple management algorithm in the web app. Even though there are co-running applications, the results show our approach dynamically enables a number of web workers close to the optimal. Our proposal, which is independent of the web browser, overcomes the lack of knowledge of the underlying processor architecture as well as dynamic resources availability changes.Peer ReviewedPostprint (author's final draft