Selective dynamic serialization for reducing energy consumption in hardware transactional memory systems

In the search for new paradigms to simplify multithreaded programming, Transactional Memory (TM) is currently being advocated as a promising alternative to deadlock-prone lock-based synchronization. In this way, future many-core CMP architectures may need to provide hardware support for TM. On the other hand, power dissipation constitutes a first class consideration in multicore processor designs. In this work, we propose Selective Dynamic Serialization (SDS) as a new technique to improve energy consumption without degrading performance in applications with conflicting transactions by avoiding wasted work due to aborted transactions. Our proposal, which is implemented on top of a hardware transactional memory (HTM) system with an eager conflict management policy, detects and serializes conflicting transactions dynamically (at run-time). In its simplest form, in case of conflict, one transaction is allowed to continue whilst the rest are completely stalled. Once the executing transaction has finished, it wakes up several of the stalling transactions. More elaborated implementations of SDS try to delay this behavior until serialization of transactions is profitable, achieving the best trade-off between performance, energy savings and network traffic. SDS implementations differ from each other in the condition that triggers the serialization mode. We have evaluated several SDS schemes using GEMS, a full-system simulator implementing the LogTM-SE Eager–Eager HTM system, and several benchmarks from the STAMP suite. Results for a 16-core CMP show that SDS obtains reductions of 6 % on average in energy consumption (more than 20 % in high contention scenarios) in a wide range of benchmarks without affecting, on average, execution time. At the same time, network traffic level is also reduced by 22 %.     

Functional data analysis in shape analysis

Mid-level processes on images often return outputs in functional form. In this context the use of functional data analysis (FDA) in image analysis is considered. In particular, attention is focussed on shape analysis, where the use of FDA in the functional approach (contour functions) shows its superiority over other approaches, such as the landmark based approach or the set theory approach, on two different problems (principal component analysis and discriminant analysis) in a well-known database of bone outlines. Furthermore, a problem that has hardly ever been considered in the literature is dealt with: multivariate functional discrimination. A discriminant function based on independent component analysis for indicating where the differences between groups are and what their level of discrimination is, is proposed. The classification results obtained with the methodology are very promising. Finally, an analysis of hippocampal differences in Alzheimer’s disease is carried out.     

Chemical Defenses Against Fish Predation in Three Brazilian Octocorals: 11β,12β-Epoxypukalide as a Feeding Deterrent in Phyllogorgia dilatata

The feeding-deterrence properties of crude extracts of three Brazilian octocoral species, Neospongodes atlantica Kükenthal (Alcyonacea, Nephtheidae), Plexaurella regia Castro (Gorgonacea, Plexauridae), and Phyllogorgia dilatata Esper (Gorgonacea, Gorgoniidae), were investigated. All the extracts were incorporated into food strips at the concentrations occurring in the living organisms. Crude extract and its ethyl acetate fraction obtained from P. dilatata collected in Armação dos Búzios (Rio de Janeiro State), when incorporated into artificial diets and tested in the habitat of origin, reduced consumption of food strips by fishes, relative to controls. Crude extracts from two octocoral species collected at the National Marine Park of Abrolhos (Bahia State), N. atlantica and P. regia, had no apparent feeding-deterrence properties; in fact, they seemed to stimulate feeding. Bioassay-guided fractionation of the bioactive P. dilatata crude extract revealed that the deterrent property was restricted to a medium polarity fraction. Field palatability experiments with two pure compounds isolated from this fraction revealed that the furanocembranolide 11,12-epoxypukalide is a potent feeding deterrent produced by P. dilatata against fish. Apparently, furanocembranolides are a particular class of compounds with feeding deterrent properties, protecting some octocorals from potential fish predator species in both tropical and temperate environments.     

Notes on a recursive procedure for point estimation

Summary A procedure for making inference about parameters of a statistical model is proposed which uses a general and easy to implement recursive system. Unlike the a full Bayesian approach, this procedure does not require a particular choice of prior, only a suitable (mean, variance)-parametrised class. Unlike maximum likelihood, it takes into account the global structure of the likelihood, and seems reasonable even when pathological cases of the likelihood arise. An heuristic large-sample argument is also considered.     

Nonlinear image representation for efficient perceptual coding.

Image compression systems commonly operate by transforming the input signal into a new representation whose elements are independently quantized. The success of such a system depends on two properties of the representation. First, the coding rate is minimized only if the elements of the representation are statistically independent. Second, the perceived coding distortion is minimized only if the errors in a reconstructed image arising from quantization of the different elements of the representation are perceptually independent. We argue that linear transforms cannot achieve either of these goals and propose, instead, an adaptive nonlinear image representation in which each coefficient of a linear transform is divided by a weighted sum of coefficient amplitudes in a generalized neighborhood. We then show that the divisive operation greatly reduces both the statistical and the perceptual redundancy amongst representation elements. We develop an efficient method of inverting this transformation, and we demonstrate through simulations that the dual reduction in dependency can greatly improve the visual quality of compressed images.     

Archetypal analysis: Contributions for estimating boundary cases in multivariate accommodation problem

The use of archetypal analysis is proposed in order to determine a set of representative cases that entail a certain percentage of the population, in the accommodation problem. A well-known anthropometric database has been used in order to compare our methodology with the common used PCA-approach, showing the advantages of our methodology: the level of accommodation is reached unlike the PCA approach, no more adjustments are necessary, the user can decide the number of archetypes to consider or leave the selection by a criterion. Unlike PCA, the objective of the archetypal analysis is obtaining extreme individuals, so it is the appropriate statistical technique for solving this type of problem. Archetypes cannot be obtained with PCA even if we consider all the components, as we show in the application.     

Perceptually weighted optical flow for motion-based segmentation inMPEG-4 paradigm

In the MPEG-4 paradigm, the sequence must be described in terms of meaningful objects. This meaningful, high-level representation should emerge from low-level primitives such as optical flow and prediction error which are the basic elements of previous-generation video coders. The accuracy of the high-level models strongly depends on the robustness of the primitives used. It is shown how perceptual weighting in optical flow computation gives rise to better motion estimates which consistently improve motion-based segmentation compared to equivalent unweighted motion estimates     

The Sesterterpene Variabilin as a Fish-Predation Deterrent in the Western Atlantic Sponge Ircinia strobilina

The furanosesterterpene variabilin was identified in an unpalatable crude extract and proved to be a feeding deterrent when offered at 0.23% of artificial diet dry weight to reef fishes in field assays. The icthyodeterrent property of variabilin was expressed when food pellets for the palatability assays were made with calcium alginate, but not carrageenan. Variabilin probably failed to show deterrent activity in the carageenan matrix because of decomposition during the necessary heat treatment.     

From Nerode’s congruence to suffix automata with mismatches

In this paper we focus on the minimal deterministic finite automaton _Sk$S_k$ that recognizes the set of suffixes of a word w$w$ up to k$k$ errors. As first result we give a characterization of the Nerode’s right-invariant congruence that is associated with _Sk$S_k$. This result generalizes the classical characterization described in [A. Blumer, J. Blumer, D. Haussler, A. Ehrenfeucht, M. Chen, J. Seiferas, The smallest automaton recognizing the subwords of a text, Theoretical Computer Science, 40, 1985, 31–55]. As second result we present an algorithm that makes use of _Sk$S_k$ to accept in an efficient way the language of all suffixes of w$w$ up to k$k$ errors in every window of size r$r$ of a text, where r$r$ is the repetition index of w$w$. Moreover, we give some experimental results on some well-known words, like prefixes of Fibonacci and Thue-Morse words. Finally, we state a conjecture and an open problem on the size and the construction of the suffix automaton with mismatches.