bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of blueberry supplementation on measures of functional mobility in older adults
Authors: Schrager Matthew A. , Hilton James , Gould Richard , Kelly Valerie E.
Published: January 2015

Limited functional mobility in older adults has been associated with declines in tests of motor, psychomotor, and executive function. Animal studies have demonstrated reversals in indices of motor and psychomotor function via supplementation with polyphenolic-rich foods such as blueberries. The purpose of this study was to examine whether 6 weeks of daily consumption of 2 cups of frozen blueberries affects functional mobility in older adults. Pre- and post-intervention assessments of grip strength, simple reaction time, adaptive gait, and executive function were completed for older adults (age >60 years) partially randomly assigned to a blueberry (BB) supplementation or a carrot juice drink control (CAR) group. Paired t tests were used to assess within-group effects for outcome variables in each supplementation group, and a mixed-model analysis of covariance (ANCOVA) was used to determine group (CAR vs. BB) differences. Mixed-model analysis indicated that the BB group demonstrated significant improvements relative to the CAR group in performance (i.e., number of step errors) of a challenging dual-task adaptive gait test that were independent of differences in gait speed. Within only the BB group, significant improvements were also seen in 3 other measures (i.e., usual gait speed; number of step errors during single-task adaptive gait; and gait speed during dual-task adaptive gait). These preliminary findings support the hypothesis that blueberry supplementation may provide an effective countermeasure to age-related declines in functional mobility and serve as justification for an expansion to larger trials to more fully assess this nonpharmacologic approach to maintaining optimal mobility and independence.
To log or not to log? How forestry fits with the goals of First Nations in British Columbia
Authors: Nikolakis William , Nelson Harry
Published: January 2015

Commercial forestry has played an important role in the Canadian economy. Yet, First Nations (FNs) communities have not shared equitably in the benefits. Since 2002, the government of British Columbia (BC) has actively sought to address this inequity by increasing the volume of forest harvesting tenures to FNs. The rationale is that rights to harvest will also enhance economic and then social outcomes, as well as address broader legal and political disputes. However, whether these rights can translate into the expected benefits has received little attention. This paper seeks to help address this knowledge gap by interviewing FNs experts and forestry professionals in BC to understand the long-term goals of FNs in forestry, to strategically evaluate how (and if) opportunities from forestry arise, and to identify institutional factors that influence successful participation in forestry. What we found is that forest tenure can promote economic outcomes, but it often comes at the expense of other intrinsic forest values. We conclude that a rights-based approach alone will not achieve the diverse outcomes related to forestry without effective governance by FNs to evaluate and capitalize on the opportunity in ways that are legitimate to the individual community’s values.
Genetic control of Eucalyptus globulus harvest traits
Authors: Hamilton Matthew G. , Acuna Mauricio , Wiedemann John C. , Mitchell Rick , Pilbeam David J. , Brown Mark W. , Potts Brad M.
Published: January 2015

The cost of harvesting short-rotation plantation eucalypts can be in excess of AU$2500·ha−1. Despite this high cost, the extent to which harvesting productivity is affected by tree genetics is not well understood. We address this issue in a study of two 10-year-old genetic field trials of Eucalyptus globulus Labill. in Australia. Standing-tree traits analysed were survival, diameter at breast height, basal area, and stem straightness and forking. Harvest traits analysed were volume, time, and productivity. Genetic group and within-group genetic variation (additive and dominance), stand-level family variation, phenotypic and genetic correlations, and the effects of inbreeding were estimated for these traits. The different scenarios studied showed that plantation harvest productivity was affected by tree genetics to some degree but was mainly affected through positive covariation with stem diameter. Harvest productivity is thus unlikely to have been adversely affected by past selection. Although no significant additive or dominance genetic variation in stem forking or straightness was detected, weak phenotypic correlations were consistent with harvest productivity being higher in straighter trees with no forking. High inbreeding depression was evident for growth and survival; however, in open-pollinated progeny, this resulted in only a slight reduction in harvest productivity (5.5%) compared with out-crossed progeny.
Growth and characterization of semi-organic nonlinear optical crystals of l-leucine hydrochlorobromide (LEHCBr)
Authors: Priakumari R. Omegala , Sheba S. Grace Sahaya , Gunasekaran M.
Published: January 2015

l-Leucine hydrochlorobromide (LEHCBr), a semi-organic nonlinear optical material, was synthesized and grown as single crystal by slow evaporation method at ambient temperature. The powder X-ray diffraction pattern of the grown LEHCBr crystal was indexed and compared with single crystal X-ray diffraction data. Functional groups present in the sample were identified by FT-IR analysis. The grown crystal shows a cut off wavelength of 247 nm from the recorded UV–vis–IR spectrum. The thermal stability and melting temperature of LEHCBr were determined from TGA/DTA curves. The Vickers hardness was evaluated to be 71.9 kg/mm2 using Vickers microhardness tester. The dielectric behavior of the crystal was studied at different temperatures. The positive photo conducting nature of the LEHCBr crystal was confirmed by photoconductivity study. The Kurtz–Perry powder study revealed the SHG efficiency of LEHCBr as 4.6 times higher than that of KDP.
Gaussian wave packet states of a generalized inverted harmonic oscillator with time-dependent mass and frequency
Authors: Pedrosa I.A. , de Lima Alberes Lopes , de M. Carvalho Alexandre M.
Published: January 2015

We derive quantum solutions of a generalized inverted or repulsive harmonic oscillator with arbitrary time-dependent mass and frequency using the quantum invariant method and linear invariants, and write its wave functions in terms of solutions of a second-order ordinary differential equation that describes the amplitude of the damped classical inverted oscillator. Afterwards, we construct Gaussian wave packet solutions and calculate the fluctuations in coordinate and momentum, the associated uncertainty relation, and the quantum correlations between coordinate and momentum. As a particular case, we apply our general development to the generalized inverted Caldirola–Kanai oscillator.
Abnormal Rho-associated kinase activity contributes to the dysfunctional myogenic response of cerebral arteries in type 2 diabetes
Authors: Abd-Elrahman Khaled S. , Walsh Michael P. , Cole William C.
Published: January 2015

The structural and functional integrity of the brain, and therefore, cognition, are critically dependent on the appropriate control of blood flow within the cerebral circulation. Inadequate flow leads to ischemia, whereas excessive flow causes small vessel rupture and (or) blood–brain-barrier disruption. Cerebral blood flow is controlled through the interplay of several physiological mechanisms that regulate the contractile state of vascular smooth muscle cells (VSMCs) within the walls of cerebral resistance arteries and arterioles. The myogenic response of cerebral VSMCs is a key mechanism that is responsible for maintaining constant blood flow during variations in systemic pressure, i.e., flow autoregulation. Inappropriate myogenic control of cerebral blood flow is associated with, and prognostic of, neurological deterioration and poor outcome in patients with several conditions, including type 2 diabetes. Here, we review recent advances in our understanding of the role of inappropriate Rho-associated kinase activity as a cause of impaired myogenic regulation of cerebral arterial diameter in type 2 diabetes.
New exotic 4-manifolds via Luttinger surgery on Lefschetz fibrations
Authors: Akhmedov Anar , Saglam Kadriye Nur
Published: January 2015

In [Small exotic 4-manifolds, Algebr. Geom. Topol.8 (2008) 1781–1794], the first author constructed the first known example of exotic minimal symplectic[Formula: see text] and minimal symplectic 4-manifold that is homeomorphic but not diffeomorphic to [Formula: see text]. The construction in [Small exotic 4-manifolds, Algebr. Geom. Topol.8 (2008) 1781–1794] uses Yukio Matsumoto's genus two Lefschetz fibrations on [Formula: see text] over 𝕊2 along with the fake symplectic 𝕊2 × 𝕊2 construction given in [Construction of symplectic cohomology 𝕊2 × 𝕊2, Proc. Gökova Geom. Topol. Conf.14 (2007) 36–48]. The main goal in this paper is to generalize the construction in [Small exotic 4-manifolds, Algebr. Geom. Topol.8 (2008) 1781–1794] using the higher genus versions of Matsumoto's fibration constructed by Mustafa Korkmaz and Yusuf Gurtas on [Formula: see text] for any k ≥ 2 and n = 1, and k ≥ 1 and n ≥ 2, respectively. Using our symplectic building blocks, we also construct new symplectic 4-manifolds with the free group of rank s ≥ 1, the free product of the finite cyclic groups, and various other finitely generated groups as the fundamental group.
Apocynum venetum Leaf Attenuates Myocardial Ischemia/Reperfusion Injury by Inhibiting Oxidative Stress
Authors: Wang Wenqing , Liang Xiangyan , Fu Dong , Tie Ru , Xing Wenjuan , Ji Lele , Liu Fange , Zhang Haifeng , Li Rong
Published: January 2015

Apocynum venetum, a Chinese medicinal herb, is reported to be neuroprotective. However, whether Apocynum venetum leaf extract (AVLE) protects against ischemic myocardium remains elusive. Our present study was aimed to observe the effects of AVLE preconditioning on myocardial ischemia/reperfusion (MI/R) injury and to investigate the possible mechanisms. Rats were treated with AVLE (500 mg/kg/d, o.g.) or distilled water once daily for one week. Afterward, all the animals were subjected to 30 min of myocardial ischemia followed by 4 h of reperfusion. AVLE preconditioning for one week significantly improved cardiac function following MI/R. Meanwhile, AVLE reduced infarct size, plasma creatine kinase (CK)/lactate dehydrogenase (LDH) activities and myocardial apoptosis at the end of reperfusion in rat hearts. Moreover, AVLE preconditioning significantly inhibited superoxide generation, gp91phox expression, malonaldialdehyde formation and enhanced superoxide dismutase (SOD) activity in I/R hearts. Furthermore, AVLE treatment increased Akt and extracellular regulated protein kinases 1/2 (ERK1/2) phosphorylations in I/R rat heart. Either the Phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin or the ERK1/2 inhibitor PD98059 blocked AVLE-stimulated anti-oxidative effects and cardioprotection. Our study demonstrated for the first time that AVLE reduces oxidative stress and exerts cardioprotection against MI/R injury in rats.
Topological symmetry groups of Möbius ladders
Authors: Flapan Erica , Lawrence Emille Davie
Published: January 2015

We classify all groups which can occur as the orientation preserving topological symmetry group of some embedding of a Möbius ladder graph in S3.
Extraction of Natural Frequencies and Mode Shapes of Rotating Beams by Variational Iteration Method
Authors: Chen Y. , Zhang J. , Zhang H. , Li X. , Zhou J.
Published: January 2015

Flapwise flexural vibration of rotating beams has been extensively studied since the 1970s. Existing methods for solving the aforementioned vibration problem range from the conventional finite element method to variable-order finite element method, Frobenius method, differential transformation method and dynamic stiffness method (DSM). Although various approximation methods are available, most of these methods are based on perturbation or discretization of the governing equation, often leading to tedious calculations. This paper re-examines flapwise flexural vibration of rotating beams using the method of variational iteration, which is relatively new and capable of providing accurate solutions for eigenvalue problems. The extracted natural frequencies and mode shapes for sample rotating beams with various rotational speeds and hub radii are compared with existing results that were published in the open literature.
Sequence-based prediction of transcription upregulation by auxin in plants
Authors: Ponomarenko Petr M. , Ponomarenko Mikhail P.
Published: January 2015

Auxin is one of the main regulators of growth and development in plants. Prediction of auxin response based on gene sequence is of high importance. We found the TGTCNC consensus of 111 known natural and artificially mutated auxin response elements (AuxREs) with measured auxin-caused relative increase in genes' transcription levels, so-called either "a response to auxin" or "an auxin response." This consensus was identical to the most cited AuxRE motif. Also, we found several DNA sequence features that correlate with auxin-caused increase in genes' transcription levels, namely: number of matches with TGTCNC, homology score based on nucleotide frequencies at the consensus positions, abundances of five trinucleotides and five B-helical DNA features around these known AuxREs. We combined these correlations using a four-step empirical model of auxin response based on a gene's sequence with four steps, namely: (1) search for AuxREs with no auxin; (2) stop at the found AuxRE; (3) repression of the basal transcription of the gene having this AuxRE; and (4) manifold increase of this gene's transcription in response to auxin. Independently measured increases in transcription levels in response to auxin for 70 Arabidopsis genes were found to significantly correlate with predictions of this equation (r = 0.44, p < 0.001) as well as with TATA-binding protein (TBP)'s affinity to promoters of these genes and with nucleosome packing of these promoters (both, p < 0.025). Finally, we improved our equation for prediction of a gene's transcription increase in response to auxin by taking into account TBP-binding and nucleosome packing (r = 0.53, p < 10-6). Fisher's F-test validated the significant impact of both TBP/promoter-affinity and promoter nucleosome on auxin response in addition to those of AuxRE, F = 4.07, p < 0.025. It means that both TATA-box and nucleosome should be taken into account to recognize transcription factor binding sites upon DNA sequences: in the case of the TATA-less nucleosome-rich promoters, recognition scores must be higher than in the case of the TATA-containing nucleosome-free promoters at the same transcription activity.
Embedding assisted prediction architecture for event trigger identification
Authors: Nie Yifan , Rong Wenge , Zhang Yiyuan , Ouyang Yuanxin , Xiong Zhang
Published: January 2015

Molecular events normally have significant meanings since they describe important biological interactions or alternations such as binding of a protein. As a crucial step of biological event extraction, event trigger identification has attracted much attention and many methods have been proposed. Traditionally those methods can be categorised into rule-based approach and machine learning approach and machine learning-based approaches have demonstrated its potential and outperformed rule-based approaches in many situations. However, machine learning-based approaches still face several challenges among which a notable one is how to model semantic and syntactic information of different words and incorporate it into the prediction model. There exist many ways to model semantic and syntactic information, among which word embedding is an effective one. Therefore, in order to address this challenge, in this study, a word embedding assisted neural network prediction model is proposed to conduct event trigger identification. The experimental study on commonly used dataset has shown its potential. It is believed that this study could offer researchers insights into semantic-aware solutions for event trigger identification.
The study of unfoldable self-avoiding walks — Application to protein structure prediction software
Authors: Guyeux Christophe , Nicod Jean-Marc , Philippe Laurent , Bahi Jacques M.
Published: January 2015

Self-avoiding walks (SAWs) are the source of very difficult problems in probability and enumerative combinatorics. They are of great interest as, for example, they are the basis of protein structure prediction (PSP) in bioinformatics. The authors of this paper have previously shown that, depending on the prediction algorithm, the sets of obtained walk conformations differ: For example, all the SAWs can be generated using stretching-based algorithms whereas only the unfoldable SAWs can be obtained with methods that iteratively fold the straight line. A deeper study of (non-)unfoldable SAWs is presented in this paper. The contribution is first a survey of what is currently known about these sets. In particular, we provide clear definitions of various subsets of SAWs related to pivot moves (unfoldable and non-unfoldable SAWs, etc.) and the first results that we have obtained, theoretically or computationally, on these sets. Then a new theorem on the number of non-unfoldable SAWs is demonstrated. Finally, a list of open questions is provided and the consequences on the PSP problem is proposed.
From the static interactome to dynamic protein complexes: Three challenges
Authors: Yong Chern Han , Wong Limsoon
Published: January 2015

Protein interactions and complexes behave in a dynamic fashion, but this dynamism is not captured by interaction screening technologies, and not preserved in protein–protein interaction (PPI) networks. The analysis of static interaction data to derive dynamic protein complexes leads to several challenges, of which we identify three. First, many proteins participate in multiple complexes, leading to overlapping complexes embedded within highly-connected regions of the PPI network. This makes it difficult to accurately delimit the boundaries of such complexes. Second, many condition- and location-specific PPIs are not detected, leading to sparsely-connected complexes that cannot be picked out by clustering algorithms. Third, the majority of complexes are small complexes (made up of two or three proteins), which are extra sensitive to the effects of extraneous edges and missing co-complex edges. We show that many existing complex-discovery algorithms have trouble predicting such complexes, and show that our insight into the disparity between the static interactome and dynamic protein complexes can be used to improve the performance of complex discovery.
Dynamics of one-prey two-predator system with square root functional response and time lag
Authors: Misra O. P. , Sinha Poonam , Singh Chhatrapal
Published: January 2015

Animals grouping together is one of the most interesting phenomena in population dynamics and different functional responses as a result of prey–predator forming groups have been considered by many authors in their models. In the present paper we have considered a model for one prey and two competing predator populations with time lag and square root functional response on account of herd formation by prey. It is shown that due to the inclusion of another competing predator, the underlying system without delay becomes more stable and limit cycles do not occur naturally. However, after considering the effect of time lag in the basic system, limit cycles appear in the case of all equilibrium points when delay time crosses some critical value. From the numerical simulation, it is observed that the length of delay is minimum when only prey population survives and it is maximum when all the populations coexist.
Stability analysis and optimal control of an epidemic model with vaccination
Authors: Sharma Swarnali , Samanta G. P.
Published: January 2015

In this paper, we have developed a compartment of epidemic model with vaccination. We have divided the total population into five classes, namely susceptible, exposed, infective, infective in treatment and recovered class. We have discussed about basic properties of the system and found the basic reproduction number (R0) of the system. The stability analysis of the model shows that the system is locally as well as globally asymptotically stable at disease-free equilibrium E0when R0< 1. When R0> 1 endemic equilibrium E1exists and the system becomes locally asymptotically stable at E1under some conditions. We have also discussed the epidemic model with two controls, vaccination control and treatment control. An objective functional is considered which is based on a combination of minimizing the number of exposed and infective individuals and the cost of the vaccines and drugs dose. Then an optimal control pair is obtained which minimizes the objective functional. Our numerical findings are illustrated through computer simulations using MATLAB. Epidemiological implications of our analytical findings are addressed critically.
Octree-Based 3D Logic and Computation of Spatial Relationships in Live Video Query Processing
Authors: Ye Jun , Hua Kien A.
Published: January 2015

Live video computing (LVC) on distributed smart cameras has many important applications; and a database approach based on a Live Video DataBase Management System (LVDBMS) has shown to be effective for general LVC application development. The performance of such a database system relies on accurate interpretation of spatial relationships among objects in the live video. With the popularity of affordable depth cameras, 3D spatial computation techniques have been applied. However, the 3D object models currently used are expensive to compute, and offer limited scalability. We address this drawback in this article by proposing an octree-based 3D spatial logic and presenting algorithms for computing 3D spatial relationships using depth cameras. To support continuous query processing on live video streams, we also develop a GPU-based implementation of the proposed technique to further enhance scalability for real-time applications. Extensive performance studies based on a public RGB-D dataset as well as the LVDBMS prototype demonstrates the correctness and efficiency of our techniques.
Spatial-Temporal Tag Mining for Automatic Geospatial Video Annotation
Authors: Yin Yifang , Shen Zhijie , Zhang Luming , Zimmermann Roger
Published: January 2015

Videos are increasingly geotagged and used in practical and powerful GIS applications. However, video search and management operations are typically supported by manual textual annotations, which are subjective and laborious. Therefore, research has been conducted to automate or semi-automate this process. Since a diverse vocabulary for video annotations is of paramount importance towards good search results, this article proposes to leverage crowdsourced data from social multimedia applications that host tags of diverse semantics to build a spatio-temporal tag repository, consequently acting as input to our auto-annotation approach. In particular, to build the tag store, we retrieve the necessary data from several social multimedia applications, mine both the spatial and temporal features of the tags, and then refine and index them accordingly. To better integrate the tag repository, we extend our previous approach by leveraging the temporal characteristics of videos as well. Moreover, we set up additional ranking criteria on the basis of tag similarity, popularity and location bias. Experimental results demonstrate that, by making use of such a tag repository, the generated tags have a wide range of semantics, and the resulting rankings are more consistent with human perception.
General Document Retrieval in Compact Space
Authors: Navarro Gonzalo , Puglisi Simon J. , Valenzuela Daniel
Published: January 2015

Given a collection of documents and a query pattern,
document retrieval
is the problem of obtaining documents that are relevant to the query. The collection is available beforehand so that a data structure, called an index, can be built on it to speed up queries. While initially restricted to natural language text collections, document retrieval problems arise nowadays in applications like bioinformatics, multimedia databases, and web mining. This requires a more general setup where text and pattern can be general sequences of symbols, and the classical inverted indexes developed for words cannot be applied. While linear-space time-optimal solutions have been developed for most interesting queries in this general case, space usage is a serious problem in practice.

In this article, we develop compact data structures that solve various important document retrieval problems on general text collections. More specifically, we provide practical solutions for listing the documents where a query pattern appears, together with its frequency in each document, and for listing
k
documents where a query pattern appears most frequently. Some of our techniques build on existing theoretical proposals, while others are new. In particular, we introduce a novel grammar-based compressed bitmap representation that may be of independent interest when dealing with repetitive sequences.

Ours are the first practical indexes that use less space when the text collection is compressible. Our experimental results show that, in various real-life text collections, our data structures are significantly smaller than the most space-efficient previous solutions, using up to half the space without noticeably increasing the query time. Overall, document listing can be carried out in 10 to 40 milliseconds for patterns that appear 100 to 10,000 times in the collection, whereas top-
k
retrieval is carried out in
k
to 10
k
milliseconds.
Paired and Altruistic Kidney Donation in the UK
Authors: Manlove David F. , O’malley Gregg
Published: January 2015

We study the computational problem of identifying optimal sets of kidney exchanges in the UK. We show how to expand an integer programming-based formulation due to Roth et al. [2007] in order to model the criteria that constitute the UK definition of optimality. The software arising from this work has been used by the National Health Service Blood and Transplant to find optimal sets of kidney exchanges for their National Living Donor Kidney Sharing Schemes since July 2008. We report on the characteristics of the solutions that have been obtained in matching runs of the scheme since this time. We then present empirical results arising from experiments on the real datasets that stem from these matching runs, with the aim of establishing the extent to which the particular optimality criteria that are present in the UK influence the structure of the solutions that are ultimately computed. A key observation is that allowing four-way exchanges would be likely to lead to a moderate number of additional transplants.
Advanced Coarsening Schemes for Graph Partitioning
Authors: Safro Ilya , Sanders Peter , Schulz Christian
Published: January 2015

The graph partitioning problem is widely used and studied in many practical and theoretical applications. Today, multilevel strategies represent one of the most effective and efficient generic frameworks for solving this problem on large-scale graphs. Most of the attention in designing multilevel partitioning frameworks has been on the refinement phase. In this work, we focus on the coarsening phase, which is responsible for creating structures similar to the original but smaller graphs. We compare different matching- and AMG-based coarsening schemes, experiment with the algebraic distance between nodes, and demonstrate computational results on several classes of graphs that emphasize the running time and quality advantages of different coarsening schemes.
Progress in Case-Based Planning
Authors: Borrajo Daniel , Roubíčková Anna , Serina Ivan
Published: January 2015

Case-based planning (CBP) is an approach to automated planning that tries to save computational effort by reusing previously found solutions. In 2001, Spalazzi published a survey of work in CBP; here, we present an updated overview of systems that have contributed to the evolution of the field or addressed some issues related to planning by reuse in a novel way. The article presents relevant planners so that readers gain insight into the operation of these systems. This analysis will allow readers to understand the approaches both in the quality of the solutions and in the complexity of finding them.
Improving Multibank Memory Access Parallelism with Lattice-Based Partitioning
Authors: Cilardo Alessandro , Gallo Luca
Published: January 2015

Emerging architectures, such as reconfigurable hardware platforms, provide the unprecedented opportunity of customizing the memory infrastructure based on application access patterns. This work addresses the problem of automated memory partitioning for such architectures, taking into account potentially parallel data accesses to physically independent banks. Targeted at affine static control parts (SCoPs), the technique relies on the Z-polyhedral model for program analysis and adopts a partitioning scheme based on integer lattices. The approach enables the definition of a solution space including previous works as particular cases. The problem of minimizing the total amount of memory required across the partitioned banks, referred to as storage minimization throughout the article, is tackled by an optimal approach yielding asymptotically zero memory waste or, as an alternative, an efficient approach ensuring arbitrarily small waste. The article also presents a prototype toolchain and a detailed step-by-step case study demonstrating the impact of the proposed technique along with extensive comparisons with alternative approaches in the literature.
Mechanistic Analytical Modeling of Superscalar In-Order Processor Performance
Authors: Breughe Maximilien B. , Eyerman Stijn , Eeckhout Lieven
Published: January 2015

Superscalar in-order processors form an interesting alternative to out-of-order processors because of their energy efficiency and lower design complexity. However, despite the reduced design complexity, it is nontrivial to get performance estimates or insight in the application--microarchitecture interaction without running slow, detailed cycle-level simulations, because performance highly depends on the order of instructions within the application’s dynamic instruction stream, as in-order processors stall on interinstruction dependences and functional unit contention. To limit the number of detailed cycle-level simulations needed during design space exploration, we propose a mechanistic analytical performance model that is built from understanding the internal mechanisms of the processor.

The mechanistic performance model for superscalar in-order processors is shown to be accurate with an average performance prediction error of 3.2% compared to detailed cycle-accurate simulation using gem5. We also validate the model against hardware, using the ARM Cortex-A8 processor and show that it is accurate within 10% on average. We further demonstrate the usefulness of the model through three case studies: (1) design space exploration, identifying the optimum number of functional units for achieving a given performance target; (2) program--machine interactions, providing insight into microarchitecture bottlenecks; and (3) compiler--architecture interactions, visualizing the impact of compiler optimizations on performance.
Studying Optimal Spilling in the Light of SSA
Authors: Colombet Quentin , Brandner Florian , Darte Alain
Published: January 2015

Recent developments in register allocation, mostly linked to static single assignment (SSA) form, have shown the benefits of decoupling the problem in two phases: a first
spilling
phase places load and store instructions so that the register pressure at all program points is small enough, and a second
assignment
and
coalescing
phase maps the variables to physical registers and reduces the number of move instructions among registers. This article focuses on the first phase, for which many open questions remain: in particular, we study the notion of optimal spilling (what can be expressed?) and the impact of SSA form (does it help?).

To identify the important features for optimal spilling on load-store architectures, we develop a new integer linear programming formulation, more accurate and expressive than previous approaches. Among other features, we can express SSA ϕ-functions, memory-to-memory copies, and the fact that a value can be stored simultaneously in a register and in memory. Based on this formulation, we present a thorough analysis of the results obtained for the SPECINT 2000 and EEMBC 1.1 benchmarks, from which we draw, among others, the following conclusions: (1) rematerialization is extremely important; (2) SSA complicates the formulation of optimal spilling, especially because of memory coalescing when the code is not in conventional SSA (CSSA); (3) microarchitectural features are significant and thus have to be accounted for; and (4) significant savings can be obtained in terms of static spill costs, cache miss rates, and dynamic instruction counts.
Compiler-Directed Power Management for Superscalars
Authors: Haj-Yihia Jawad , Asher Yosi Ben , Rotem Efraim , Yasin Ahmad , Ginosar Ran
Published: January 2015

Modern superscalar CPUs contain large complex structures and diverse execution units, consuming wide dynamic power range. Building a power delivery network for the worst-case power consumption is not energy efficient and often is impossible to fit in small systems. Instantaneous power excursions can cause voltage droops. Power management algorithms are too slow to respond to instantaneous events. In this article, we propose a novel compiler-directed framework to address this problem. The framework is validated on a 4th Generation Intel® Core™ processor and with simulator on output trace. Up to 16% performance speedup is measured over baseline for the SPEC CPU2006 benchmarks.
GP-SIMD Processing-in-Memory
Authors: Morad Amir , Yavits Leonid , Ginosar Ran
Published: January 2015

GP-SIMD, a novel hybrid general-purpose SIMD computer architecture, resolves the issue of data synchronization by in-memory computing through combining data storage and massively parallel processing. GP-SIMD employs a two-dimensional access memory with modified SRAM storage cells and a bit-serial processing unit per each memory row. An analytic performance model of the GP-SIMD architecture is presented, comparing it to associative processor and to conventional SIMD architectures. Cycle-accurate simulation of four workloads supports the analytical comparison. Assuming a moderate die area, GP-SIMD architecture outperforms both the associative processor and conventional SIMD coprocessor architectures by almost an order of magnitude while consuming less power.
The Impact of the SIMD Width on Control-Flow and Memory Divergence
Authors: Schaub Thomas , Moll Simon , Karrenberg Ralf , Hack Sebastian
Published: January 2015

Power consumption is a prevalent issue in current and future computing systems. SIMD processors amortize the power consumption of managing the instruction stream by executing the same instruction in parallel on multiple data. Therefore, in the past years, the SIMD width has steadily increased, and it is not unlikely that it will continue to do so. In this article, we experimentally study the influence of the SIMD width to the execution of data-parallel programs. We investigate how an increasing SIMD width (up to 1024) influences control-flow divergence and memory-access divergence, and how well techniques to mitigate them will work on larger SIMD widths. We perform our study on 76 OpenCL applications and show that a group of programs scales well up to SIMD width 1024, whereas another group of programs increasingly suffers from control-flow divergence. For those programs, thread regrouping techniques may become increasingly important for larger SIMD widths. We show what average speedups can be expected when increasing the SIMD width. For example, when switching from scalar execution to SIMD width 64, one can expect a speedup of 60.11, which increases to 62.46 when using thread regrouping. We also analyze the frequency of regular (uniform, consecutive) memory access patterns and observe a monotonic decrease of regular memory accesses from 82.6 at SIMD width 4 to 43.1% at SIMD width 1024.
Measuring Microarchitectural Details of Multi- and Many-Core Memory Systems through Microbenchmarking
Authors: Fang Zhenman , Mehta Sanyam , Yew Pen-Chung , Zhai Antonia , Greensky James , Beeraka Gautham , Zang Binyu
Published: January 2015

As multicore and many-core architectures evolve, their memory systems are becoming increasingly more complex. To bridge the latency and bandwidth gap between the processor and memory, they often use a mix of multilevel private/shared caches that are either blocking or nonblocking and are connected by high-speed network-on-chip. Moreover, they also incorporate hardware and software prefetching and simultaneous multithreading (SMT) to hide memory latency. On such multi- and many-core systems, to incorporate various memory optimization schemes using compiler optimizations and performance tuning techniques, it is crucial to have microarchitectural details of the target memory system. Unfortunately, such details are often unavailable from vendors, especially for newly released processors.

In this article, we propose a novel microbenchmarking methodology based on short elapsed-time events (SETEs) to obtain comprehensive memory microarchitectural details in multi- and many-core processors. This approach requires detailed analysis of potential interfering factors that could affect the intended behavior of such memory systems. We lay out effective guidelines to control and mitigate those interfering factors. Taking the impact of SMT into consideration, our proposed methodology not only can measure traditional cache/memory latency and off-chip bandwidth but also can uncover the details of software and hardware prefetching units not attempted in previous studies. Using the newly released Intel Xeon Phi many-core processor (with in-order cores) as an example, we show how we can use a set of microbenchmarks to determine various microarchitectural features of its memory system (many are undocumented from vendors). To demonstrate the portability and validate the correctness of such a methodology, we use the well-documented Intel Sandy Bridge multicore processor (with out-of-order cores) as another example, where most data are available and can be validated. Moreover, to illustrate the usefulness of the measured data, we do a multistage coordinated data prefetching case study on both Xeon Phi and Sandy Bridge and show that by using the measured data, we can achieve 1.3X and 1.08X performance speedup, respectively, compared to the state-of-the-art Intel ICC compiler. We believe that these measurements also provide useful insights into memory optimization, analysis, and modeling of such multicore and many-core architectures.
Cross-Loop Optimization of Arithmetic Intensity for Finite Element Local Assembly
Authors: Luporini Fabio , Varbanescu Ana Lucia , Rathgeber Florian , Bercea Gheorghe-Teodor , Ramanujam J. , Ham David A. , Kelly Paul H. J.
Published: January 2015

We study and systematically evaluate a class of composable code transformations that improve arithmetic intensity in local assembly operations, which represent a significant fraction of the execution time in finite element methods. Their performance optimization is indeed a challenging issue. Even though affine loop nests are generally present, the short trip counts and the complexity of mathematical expressions, which vary among different problems, make it hard to determine an optimal sequence of successful transformations. Our investigation has resulted in the implementation of a compiler (called COFFEE) for local assembly kernels, fully integrated with a framework for developing finite element methods. The compiler manipulates abstract syntax trees generated from a domain-specific language by introducing domain-aware optimizations for instruction-level parallelism and register locality. Eventually, it produces C code including vector SIMD intrinsics. Experiments using a range of real-world finite element problems of increasing complexity show that significant performance improvement is achieved. The generality of the approach and the applicability of the proposed code transformations to other domains is also discussed.
Compiler/Runtime Framework for Dynamic Dataflow Parallelization of Tiled Programs
Authors: Kong Martin , Pop Antoniu , Pouchet Louis-Noël , Govindarajan R. , Cohen Albert , Sadayappan P.
Published: January 2015

Task-parallel languages are increasingly popular. Many of them provide expressive mechanisms for intertask synchronization. For example, OpenMP 4.0 will integrate data-driven execution semantics derived from the StarSs research language. Compared to the more restrictive data-parallel and fork-join concurrency models, the advanced features being introduced into task-parallel models in turn enable improved scalability through load balancing, memory latency hiding, mitigation of the pressure on memory bandwidth, and, as a side effect, reduced power consumption.

In this article, we develop a systematic approach to compile loop nests into concurrent, dynamically constructed graphs of dependent tasks. We propose a simple and effective heuristic that selects the most profitable parallelization idiom for every dependence type and communication pattern. This heuristic enables the extraction of interband parallelism (cross-barrier parallelism) in a number of numerical computations that range from linear algebra to structured grids and image processing. The proposed static analysis and code generation alleviates the burden of a full-blown dependence resolver to track the readiness of tasks at runtime. We evaluate our approach and algorithms in the PPCG compiler, targeting OpenStream, a representative dataflow task-parallel language with explicit intertask dependences and a lightweight runtime. Experimental results demonstrate the effectiveness of the approach.
Transactional Read-Modify-Write Without Aborts
Authors: Ruan Wenjia , Liu Yujie , Spear Michael
Published: January 2015

Language-level transactions are said to provide “atomicity,” implying that the order of operations within a transaction should be invisible to concurrent transactions and thus that independent operations within a transaction should be safe to execute in any order. In this article, we present a mechanism for dynamically reordering memory operations within a transaction so that read-modify-write operations on highly contended locations can be delayed until the very end of the transaction. When integrated with traditional transactional conflict detection mechanisms, our approach reduces aborts on hot memory locations, such as statistics counters, thereby improving throughput and reducing wasted work. We present three algorithms for delaying highly contended read-modify-write operations within transactions, and we evaluate their impact on throughput for eager and lazy transactional systems across multiple workloads. We also discuss complications that arise from the interaction between our mechanism and the need for strong language-level semantics, and we propose algorithmic extensions that prevent errors from occurring when accesses are aggressively reordered in a transactional memory implementation with weak semantics.
Play it seriously
Authors: JafariNaimi Nassim , Meyers Eric
Published: January 2015

In this forum we highlight innovative thought, design, and research in the area of interaction design and sustainability, illustrating the diversity of approaches across HCI communities.
--- Lisa Nathan and Samuel Mann, Editors
Demo hour
Authors: Fortmann Jutta , Müller Heiko , Heuten Wilko , Boll Susanne , Kangas Jari , Akkil Deepak , Rantala Jussi , Isokoski Poika , Majaranta Päivi , Raisamo Roope , Orlov Pavel A. , Bednarik Roman , Caltenco Héctor A. , Larsen Henrik Svarrer , Hedvall Per-Olof
Published: January 2015

NordiCHI'14 conference attendees got hands-on experience with a number of great new interactive systems. Among the accepted poster, video, and demo submissions, we selected the following four prototypes to illustrate the high-quality design research displayed during the conference, which was held in Helsinki, Finland, October 26--30, 2014.
Mikael Wiberg, Lily Diaz-Kommonen, and Anna Kolehmainen, NordiCHI'14 Poster, Video, and Demo Chairs
Efficient Correction of Anomalies in Snapshot Isolation Transactions
Authors: Litz Heiner , Dias Ricardo J. , Cheriton David R.
Published: January 2015

Transactional memory systems providing snapshot isolation enable concurrent access to shared data without incurring aborts on read-write conflicts. Reducing aborts is extremely relevant as it leads to higher concurrency, greater performance, and better predictability. Unfortunately, snapshot isolation does not provide serializability as it allows certain anomalies that can lead to subtle consistency violations. While some mechanisms have been proposed to verify the correctness of a program utilizing snapshot isolation transactions, it remains difficult to repair incorrect applications. To reduce the programmer’s burden in this case, we present a technique based on dynamic code and graph dependency analysis that automatically corrects existing snapshot isolation anomalies in transactional memory programs. Our evaluation shows that corrected applications retain the performance benefits characteristic of snapshot isolation over conventional transactional memory systems.
Lessons in customer experience leadership
Authors: Courage Catherine
Published: January 2015

This forum is dedicated to maximizing the success of HCI practitioners within the frenetic world of product and service design. It focuses on UX strategy approaches, leadership, management techniques, and above all the challenge of bringing HCI to peer-level status with longstanding business disciplines such as marketing and engineering.
--- Daniel Rosenberg, Editor
Conservation Genetics and Genomics of Amphibians and Reptiles
Authors: Shaffer H. Bradley , Gidiş Müge , McCartney-Melstad Evan , Neal Kevin M. , Oyamaguchi Hilton M. , Tellez Marisa , Toffelmier Erin M.
Published: January 2015

Amphibians and reptiles as a group are often secretive, reach their greatest diversity often in remote tropical regions, and contain some of the most endangered groups of organisms on earth. Particularly in the past decade, genetics and genomics have been instrumental in the conservation biology of these cryptic vertebrates, enabling work ranging from the identification of populations subject to trade and exploitation, to the identification of cryptic lineages harboring critical genetic variation, to the analysis of genes controlling key life history traits. In this review, we highlight some of the most important ways that genetic analyses have brought new insights to the conservation of amphibians and reptiles. Although genomics has only recently emerged as part of this conservation tool kit, several large-scale data sources, including full genomes, expressed sequence tags, and transcriptomes, are providing new opportunities to identify key genes, quantify landscape effects, and manage captive breeding stocks of at-risk species.