bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparticipation predictors for championship injury and illness: cohort study at the Beijing 2015 International Association of Athletics Federations World Championships
Authors: Timpka Toomas , Jacobsson Jenny , Bargoria Victor , Périard Julien D , Racinais Sébastien , Ronsen Ola , Halje Karin , Andersson Christer , Dahlström Örjan , Spreco Armin , Edouard Pascal , Alonso Juan-Manuel
Published: November 2016

Objectives

To determine preparticipation predictors of injury and illness at a major Athletics championship.

Methods

A cohort study design was used. Before the 2015 International Association of Athletics Federations World Championships in Athletics, all 207 registered national teams were approached about partaking in a study of preparticipation health; 50 teams accepted. The athletes (n=957) in the participating teams were invited to complete a preparticipation health questionnaire (PHQ). New injuries and illnesses that occurred at the championships were prospectively recorded. Logistic regression analyses were performed with simple and multiple models using any in-championship injury and in-championship illness as outcomes.

Results

The PHQ was completed by 307 (32.1%) of the invited athletes; 116 athletes (38.3%) reported an injury symptom during the month before the championships, while 40 athletes (13%) reported an illness symptom. 20 (6.5%) of the participating athletes sustained a health problem during the championships. Endurance athletes were almost 10-fold more likely to sustain an in-championship illness than speed/power athletes (OR, 9.88; 95% CI 1.20 to 81.31; p=0.033). Participants reporting a preparticipation gradual-onset injury symptom were three times more likely (OR, 3.09; 95% CI 1.08 to 8.79; p=0.035) and those reporting an illness symptom causing anxiety were fivefold more likely (OR, 5.56; 95% CI 1.34 to 23.15; p=0.018) to sustain an in-championship injury.

Summary and conclusions

Analyses of preparticipation predictors of injury and illness at a major Athletics championship suggest that endurance athletes require particular clinical attention. Preparticipation symptoms causing anxiety are interesting predictors for in-championship health problems.
Use of combination therapy in the treatment of primary osteoporosis: protocol for a network meta-analysis of randomised trials
Authors: Lou Shenghan , Lv Houchen , Chen Yuxiang , Zhang Licheng , Tang Peifu
Published: November 2016

Introduction

The existing medications approved for treatment of primary osteoporosis can be divided into antiresorptive drugs and anabolic drugs. According to the mechanisms of action, the combined therapy may produce a synergistic effect on bone mineral density (BMD) compared with monotherapy, and thus improves the efficacy of fracture resistance. This network meta-analysis aims to compare the efficacies of different combined methods for the treatment of primary osteoporosis.

Methods and analysis

MEDLINE, EMBASE and Cochrane databases will be searched to identify all randomised controlled trials (RCTs) and quasi-RCTs that evaluate the effectiveness of combined therapy versus monotherapy for primary osteoporosis. The primary outcome will be the BMD changes at the lumbar spine and total hip, and the secondary outcome will be the risks of vertebral fracture and non-vertebral fracture. The efficacies of different combined methods will be compared via traditional pairwise meta-analysis, trial sequential analysis and Bayesian network meta-analysis. Risk of bias will be assessed using the Cochrane tool and the quality of evidence will be assessed using the Grading of Recommendations Assessment, Development and Evaluation for network meta-analysis.

Ethics and dissemination

Ethical approval is not required because this is a protocol for a systematic review without including confidential personal data or data on interventions on patients. Our results will be published in a peer-review journal.

Trial registration number

PROSPERO CRD42016038569.
Minimal muscle damage after a marathon and no influence of beetroot juice on inflammation and recovery
Authors: Clifford Tom , Allerton Dean M. , Brown Meghan A. , Harper Liam , Horsburgh Steven , Keane Karen M. , Stevenson Emma J. , Howatson Glyn
Published: November 2016

This study examined whether beetroot juice (BTJ) would attenuate inflammation and muscle damage following a marathon. Using a double blind, independent group design, 34 runners (each having completed ca. ∼16 previous marathons) consumed either BTJ or an isocaloric placebo (PLA) for 3 days following a marathon. Maximal isometric voluntary contractions (MIVC), countermovement jumps (CMJ), muscle soreness, serum cytokines, leucocytosis, creatine kinase (CK), high sensitivity C-reactive protein (hs-CRP), and aspartate aminotransferase (AST) were measured pre, post, and 2 days after the marathon. CMJ and MIVC were reduced after the marathon (P < 0.05), but no group differences were observed (P > 0.05). Muscle soreness was increased in the day after the marathon (BTJ; 45 ± 48 vs. PLA; 46 ± 39 mm) and had returned to baseline by day 2, irrespective of supplementation (P = 0.694). Cytokines (interleukin-6; IL-6, interleukin-8, tumour necrosis factor-α) were increased immediately post-marathon but apart from IL-6 had returned to baseline values by day 1 post. No interaction effects were evident for IL-6 (P = 0.213). Leucocytes increased 1.7-fold after the race and remained elevated 2 days post, irrespective of supplement (P < 0.0001). CK peaked at 1 day post marathon (BTJ: 965 ± 967, and PLA: 1141 ± 979 IU·L−1) and like AST and hs-CRP, was still elevated 2 days after the marathon (P < 0.05); however, no group differences were present for these variables. Beetroot juice did not attenuate inflammation or reduce muscle damage following a marathon, possibly because most of these indices were not markedly different from baseline values in the days after the marathon.
Superradiance initiated inside the ergoregion
Authors: Eskin Gregory
Published: November 2016

We consider the stationary metrics that have both the black hole and the ergoregion. The class of such metric contains, in particular, the Kerr metric. We study the Cauchy problem with highly oscillatory initial data supported in a neighborhood inside the ergoregion with some initial energy [Formula: see text]. We prove that when the time variable [Formula: see text] increases this solution splits into two parts: one with the negative energy [Formula: see text] ending at the event horizon in a finite time, and the second part, with the energy [Formula: see text], escaping, under some conditions, to the infinity when [Formula: see text]. Thus we get the superradiance phenomenon. In the case of the Kerr metric the superradiance phenomenon is “short-lived”, since both the solutions with positive and negative energies cross the outer event horizon in a finite time (modulo [Formula: see text]) where [Formula: see text] is a large parameter. We show that these solutions end on the singularity ring in a finite time. We study also the case of naked singularity.
Late-time cosmic acceleration: ABCD of dark energy and modified theories of gravity
Authors: Sami M. , Myrzakulov R.
Published: November 2016

We briefly review the problems and prospects of the standard lore of dark energy. We have shown that scalar fields, in principle, cannot address the cosmological constant problem. Indeed, a fundamental scalar field is faced with a similar problem dubbed naturalness. In order to keep the discussion pedagogical, aimed at a wider audience, we have avoided technical complications in several places and resorted to heuristic arguments based on physical perceptions. We presented underlying ideas of modified theories based upon chameleon mechanism and Vainshtein screening. We have given a lucid illustration of recently investigated ghost-free nonlinear massive gravity. Again, we have sacrificed rigor and confined to the basic ideas that led to the formulation of the theory. The review ends with a brief discussion on the difficulties of the theory applied to cosmology.
A congruence involving harmonic sums modulo pαqβ
Authors: Cai Tianxin , Shen Zhongyan , Jia Lirui
Published: November 2016

In 2014, Wang and Cai established the following harmonic congruence for any odd prime [Formula: see text] and positive integer [Formula: see text], [Formula: see text] where [Formula: see text] and [Formula: see text] denote the set of positive integers which are prime to [Formula: see text]. In this paper, we obtain an unexpected congruence for distinct odd primes [Formula: see text], [Formula: see text] and positive integers [Formula: see text], [Formula: see text] and the necessary and sufficient condition for [Formula: see text] Finally, we raise a conjecture that for [Formula: see text] and odd prime power [Formula: see text], [Formula: see text], [Formula: see text] However, we fail to prove it even for [Formula: see text] with three distinct prime factors.
Théorie d’Iwasawa des unités de Stark et groupe de classes
Authors: Assim Jilali , Mazigh Youness , Oukhaba Hassan
Published: November 2016

Let [Formula: see text] be a number field and let [Formula: see text] be an odd rational prime. Let [Formula: see text] be a [Formula: see text]-extension of [Formula: see text] and let [Formula: see text] be a finite extension of [Formula: see text], abelian over [Formula: see text]. In this paper we extend the classical results, e.g. [16], relating characteristic ideal of the [Formula: see text]-quotient of the projective limit of the ideal class groups to the [Formula: see text]-quotient of the projective limit of units modulo Stark units, in the non-semi-simple case, for some [Formula: see text]-irreductible characters [Formula: see text] of [Formula: see text]. The proof essentially uses the theory of Euler systems.
Implications of Local Sources to Probabilistic Tsunami Hazard Analysis in South Chinese Coastal Area
Authors: Ren Yefei , Wen Ruizhi , Zhang Peng , Yang Zhibo , Pan Rong , Li Xiaojun
Published: November 2016

The South China Sea is recognized as an area at high risk of tsunamis. The Manila Trench has long been considered as the regional source of tsunamis that might affect Chinese coastal areas, and considerable analysis of the tsunami hazard has been conducted in this area. However, there has been no consideration of other potential local sources near the coastal area. Thus, the locations of local potential tsunami sources (PTSs) along the southern coast of China and the evaluation of their impact on tsunami hazard assessment require investigation. We identified eight local PTSs for given seismic activity parameters. For the probabilistic tsunami hazard analysis (PTHA), the lower-limit earthquake magnitude was determined as 7.0, based on numerical simulation of tsunami scenarios. Six measured sites in the Pearl River Estuary and Taiwan Strait were selected for PTHA, which were referenced to Macao, Hong Kong, Daya Bay, Shantou, Xiamen, and Quanzhou. The annual rate of tsunami waves exceeding a given height [Formula: see text] was calculated for each site. The results show that the upper-limit earthquake magnitude and the relative geographical positions of the measured site of interest and the PTS are two of the most important factors in the PTHA computation. The probabilities of tsunami waves exceeding a given height [Formula: see text] within 100 years and their return periods were calculated for each site. The results show that the probability of [Formula: see text][Formula: see text]m within 100 years is 30–40% in Xiamen and Quanzhou but 5–10% in Macao and Hong Kong. If the Manila Trench were considered as a regional source, these probabilities would be higher. It is concluded that the tsunami hazard on the southern coast of China is very high and that both regional and local PTSs should be included in any future PTHA.
Synthesis and photocatalytic performance of Bi2S3/SnS2 heterojunction
Authors: Ren LiZhen , Zhang DongEn , Hao Xiao Yun , Xiao Xin , Gong Jun Yan , Wang Ming Yan , Tong ZhiWei
Published: November 2016

Bi2S3/SnS2 heterostructured photocatalysts were synthesized from BiOI, SnCl[Formula: see text]5H2O and NH2CSNH2 using an economic and simple hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy. The photodegradation activities of the Bi2S3/SnS2 heterostructured photocatalysts were estimated by degrading rhodamine B under simulated sunlight supplied by irradiating with a 350[Formula: see text]W Xe lamp. Bi2S3/SnS2 photocatalysts were prepared using varying percentages of Bi2S3. The sample containing 13% Bi2S3 had the most efficient photocatalyst performance among the tested samples. The photocatalytic mechanism involves heterojunctions formed in the Bi2S3/SnS2, which promoted effective separation of photoinduced electrons and holes.
Synthesis and characterization of multifunctional ZnBr2/PVA polymer dielectrics
Authors: Naik Jagadish , Bhajantri R. F. , Rathod Sunil G. , Sheela T. , Ravindrachary V.
Published: November 2016

Different weight percentage of ZnBr2doped poly(vinyl alcohol) (PVA) free standing composite films were prepared using solution casting method. These films were characterized for analyzing structural, dielectric, electrochemical properties. This paper mainly focused to understand the contribution of physical phenomenon on conductivity in terms of dielectric parameters. FTIR spectrum confirms the interaction between ZnBr2and PVA. Pseudo-capacitive behavior observed from cyclic voltammograms. Dielectric properties of the composites follow non-Debye type behavior. The conducting phenomenon occurs due to hopping of ions between coordination sites present in the composite and the segmental relaxation of polymer chain.
Evidence of the deformation of dykes from the Central Deccan Volcanic Province, Aurangabad, Maharashtra, India
Authors: Babar M. D. , Kaplay Ramakant D. , Mukherjee Soumyajit , Kulkarni P. S.
Published: November 2016

The Deccan Volcanic Province (DVP) covers an area of more than 500 000 km
2
. There are three major dyke swarms in this province, viz. the Narmada-Tapi, the Western Coast and the Pune-Nasik. In addition, the Nandurbar-Dhule and Pachmari dykes have also been studied. However, the Central Deccan Volcanic Province (CDVP), including parts of Aurangabad (Maharashtra, India), has received less attention than the SW, northern and NE parts of the Deccan Trap. We report on deformed/offset dykes in and around Aurangabad, in the CDVP. These dykes intrude the stratified host basaltic lava flows composed of weathered porphyritic and amygdaloidal basalt. This rheological contrast locally affected the emplacement of dykes, producing offset, the formation of sills, the curvature of dyke walls and finger-like intrusions. The offset of dykes is presumably caused by variations in local stress. The dyke swarm from the CDVP is reported for the first time. The range in the length and width of the dykes is 2.4–26.2 and 1–27 m, respectively. The dykes trend NE, which matches that of the Narmada-Tapi dyke swarm. The present study indicates that the feeder dyke(s) may have fed the basaltic lava flows of the Aurangabad region. The bent pipe vesicles indicate that the lava flowed towards the SE.
Measuring the ‘Great Unconformity’ on the North China Craton using new detrital zircon age data
Authors: He Tianchen , Zhou Ying , Vermeesch Pieter , Rittner Martin , Miao Lanyun , Zhu Maoyan , Carter Andrew , Pogge von Strandmann Philip A. E. , Shields Graham A.
Published: November 2016

New detrital zircon ages confirm that the Neoproterozoic strata of the southeastern North China Craton (NCC) are mostly of early Tonian age, but that the Gouhou Formation, previously assigned to the Tonian, is Cambrian in age. A discordant hiatus of >150–300 myr occurs across the NCC, spanning most of the late Tonian, Cryogenian, Ediacaran and early Cambrian periods. This widespread unconformable surface is akin to the Great Unconformity seen elsewhere in the world and highlights a major shift in depositional style from largely erosional, marked by low rates of net deposition, during the mid- to late Neoproterozoic to high rates of transgressive deposition during the mid- to late Cambrian. The age spectra for the southeastern NCC and northern India are consistent with a provenance affinity linking the NCC and East Gondwana by
c.
510 Ma.

Supplementary material:
Sample descriptions, sampling GPS locations and a compiled dataset of detrital zircon U–Pb LA-ICP-MS dating results are available at
https://doi.org/10.6084/m9.figshare.c.3571119
Adaptive input-aware compilation for graphics engines
Authors: Samadi Mehrzad , Hormati Amir , Mehrara Mojtaba , Lee Janghaeng , Mahlke Scott
Published: November 2016

While graphics processing units (GPUs) provide low-cost and efficient platforms for accelerating high performance computations, the tedious process of performance tuning required to optimize applications is an obstacle to wider adoption of GPUs. In addition to the programmability challenges posed by GPU's complex memory hierarchy and parallelism model, a well-known application design problem is target portability across different GPUs. However, even for a single GPU target, changing a program's input characteristics can make an already-optimized implementation of a program perform poorly. In this work, we propose Adaptic, an adaptive input-aware compilation system to tackle this important, yet overlooked, input portability problem. Using this system, programmers develop their applications in a high-level streaming language and let Adaptic undertake the difficult task of input portable optimizations and code generation. Several input-aware optimizations are introduced to make efficient use of the memory hierarchy and customize thread composition. At runtime, a properly optimized version of the application is executed based on the actual program input. We perform a head-to-head comparison between the Adaptic generated and hand-optimized CUDA programs. The results show that Adaptic is capable of generating codes that can perform on par with their hand-optimized counterparts over certain input ranges and outperform them when the input falls out of the hand-optimized programs' "comfort zone". Furthermore, we show that input-aware results are sustainable across different GPU targets making it possible to write and optimize applications once and run them anywhere.
The implicit calculus
Authors: Oliveira Bruno C.d.S. , Schrijvers Tom , Choi Wontae , Lee Wonchan , Yi Kwangkeun
Published: November 2016

Generic programming
(GP) is an increasingly important trend in programming languages. Well-known GP mechanisms, such as type classes and the C++0x concepts proposal, usually combine two features: 1) a special type of interfaces; and 2)
implicit instantiation
of implementations of those interfaces.

Scala
implicits
are a GP language mechanism, inspired by type classes, that break with the tradition of coupling implicit instantiation with a special type of interface. Instead, implicits provide only implicit instantiation, which is generalized to work for
any types
. This turns out to be quite powerful and useful to address many limitations that show up in other GP mechanisms.

This paper synthesizes the key ideas of implicits formally in a minimal and general core calculus called the implicit calculus (λ⇒), and it shows how to build source languages supporting implicit instantiation on top of it. A novelty of the calculus is its support for
partial resolution
and
higher-order rules
(a feature that has been proposed before, but was never formalized or implemented). Ultimately, the implicit calculus provides a formal model of implicits, which can be used by language designers to study and inform implementations of similar mechanisms in their own languages.
Speculative linearizability
Authors: Guerraoui Rachid , Kuncak Viktor , Losa Giuliano
Published: November 2016

Linearizability is a key design methodology for reasoning about implementations of concurrent abstract data types in both shared memory and message passing systems. It provides the illusion that operations execute sequentially and fault-free, despite the asynchrony and faults inherent to a concurrent system, especially a distributed one. A key property of linearizability is inter-object composability: a system composed of linearizable objects is itself linearizable. However, devising linearizable objects is very difficult, requiring complex algorithms to work correctly under general circumstances, and often resulting in bad average-case behavior. Concurrent algorithm designers therefore resort to speculation: optimizing algorithms to handle common scenarios more efficiently. The outcome are even more complex protocols, for which it is no longer tractable to prove their correctness.

To simplify the design of efficient yet robust linearizable protocols, we propose a new notion:
speculative linearizability
. This property is as general as linearizability, yet it allows intra-object composability: the correctness of independent protocol phases implies the correctness of their composition. In particular, it allows the designer to focus solely on the proof of an optimization and derive the correctness of the overall protocol from the correctness of the existing, non-optimized one.

Our notion of protocol phases allows processes to independently switch from one phase to another, without requiring them to reach agreement to determine the change of a phase. To illustrate the applicability of our methodology, we show how examples of speculative algorithms for shared memory and asynchronous message passing naturally fit into our framework.

We rigorously define speculative linearizability and prove our intra-object composition theorem in a trace-based as well as an automaton-based model. To obtain a further degree of confidence, we also formalize and mechanically check the theorem in the automaton-based model, using the I/O automata framework within the Isabelle interactive proof assistant. We expect our framework to enable, for the first time, scalable specifications and mechanical proofs of speculative implementations of linearizable objects.
Diderot
Authors: Chiw Charisee , Kindlmann Gordon , Reppy John , Samuels Lamont , Seltzer Nick
Published: November 2016

Research scientists and medical professionals use imaging technology, such as
computed tomography
(CT) and
magnetic resonance
imaging (MRI) to measure a wide variety of biological and physical objects. The increasing sophistication of imaging technology creates demand for equally sophisticated computational techniques to analyze and visualize the image data. Analysis and visualization codes are often crafted for a specific experiment or set of images, thus imaging scientists need support for quickly developing codes that are reliable, robust, and efficient.

In this paper, we present the design and implementation of Diderot, which is a parallel domain-specific language for biomedical image analysis and visualization. Diderot supports a high-level model of computation that is based on continuous tensor fields. These tensor fields are reconstructed from discrete image data using separable convolution kernels, but may also be defined by applying higher-order operations, such as differentiation (∇). Early experiments demonstrate that Diderot provides both a high-level concise notation for image analysis and visualization algorithms, as well as high sequential and parallel performance.
JANUS
Authors: Tripp Omer , Manevich Roman , Field John , Sagiv Mooly
Published: November 2016

This paper addresses the problem of reducing unnecessary conflicts in optimistic synchronization. Optimistic synchronization must ensure that any two concurrently executing transactions that commit are properly synchronized. Conflict detection is an approximate check for this condition. For efficiency, the traditional approach to conflict detection conservatively checks that the memory locations mutually accessed by two concurrent transactions are accessed only for reading.

We present JANUS, a parallelization system that performs conflict detection by considering sequences of operations and their composite effect on the system's state. This is done efficiently, such that the runtime overhead due to conflict detection is on a par with that of write-conflict-based detection. In certain common scenarios, this mode of refinement dramatically improves the precision of conflict detection, thereby reducing the number of false conflicts.

Our empirical evaluation of JANUS shows that this precision gain reduces the abort rate by an order of magnitude (22x on average), and achieves a speedup of up to 2.5x, on a suite of real-world benchmarks where no parallelism is exploited by the standard approach.
Proving acceptability properties of relaxed nondeterministic approximate programs
Authors: Carbin Michael , Kim Deokhwan , Misailovic Sasa , Rinard Martin C.
Published: November 2016

Approximate program transformations such as skipping tasks [29, 30], loop perforation [21, 22, 35], reduction sampling [38], multiple selectable implementations [3, 4, 16, 38], dynamic knobs [16], synchronization elimination [20, 32], approximate function memoization [11],and approximate data types [34] produce programs that can execute at a variety of points in an underlying performance versus accuracy tradeoff space. These transformed programs have the ability to trade accuracy of their results for increased performance by dynamically and nondeterministically modifying variables that control their execution.

We call such transformed programs
relaxed
programs because they have been extended with additional nondeterminism to relax their semantics and enable greater flexibility in their execution.

We present language constructs for developing and specifying
relaxed
programs. We also present proof rules for reasoning about
properties
[28] which the program must satisfy to be acceptable. Our proof rules work with two kinds of acceptability properties:
acceptability properties
[28], which characterize desired relationships between the values of variables in the original and relaxed programs, and
unary
acceptability properties, which involve values only from a single (original or relaxed) program. The proof rules support a
staged
reasoning approach in which the majority of the reasoning effort works with the original program. Exploiting the common structure that the original and relaxed programs share, relational reasoning transfers reasoning effort from the original program to prove properties of the relaxed program.

We have formalized the dynamic semantics of our target programming language and the proof rules in Coq and verified that the proof rules are sound with respect to the dynamic semantics. Our Coq implementation enables developers to obtain fully machine-checked verifications of their relaxed programs.
Engage
Authors: Fischer Jeffrey , Majumdar Rupak , Esmaeilsabzali Shahram
Published: November 2016

Many modern applications are built by combining independently developed packages and services that are distributed over many machines with complex inter-dependencies. The assembly, installation, and management of such applications is hard, and usually performed either manually or by writing customized scripts. We present Engage, a system for configuring, installing, and managing complex application stacks. Engage consists of three components: a domain-specific model to describe component metadata and inter-component dependencies; a constraint-based algorithm that takes a partial installation specification and computes a full installation plan; and a runtime system that co-ordinates the deployment of the application across multiple machines and manages the deployed system. By explicitly modeling configuration metadata and inter-component dependencies, Engage enables static checking of application configurations and automated, constraint-driven, generation of installation plans across multiple machines. This reduces the tedious manual process of application configuration, installation, and management.

We have implemented Engage and we have used it to successfully host a number of applications. We describe our experiences in using Engage to manage a generic platform that hosts Django applications in the cloud or on premises.
Speculative separation for privatization and reductions
Authors: Johnson Nick P. , Kim Hanjun , Prabhu Prakash , Zaks Ayal , August David I.
Published: November 2016

Automatic parallelization is a promising strategy to improve application performance in the multicore era. However, common programming practices such as the reuse of data structures introduce artificial constraints that obstruct automatic parallelization. Privatization relieves these constraints by replicating data structures, thus enabling scalable parallelization. Prior privatization schemes are limited to arrays and scalar variables because they are sensitive to the layout of dynamic data structures. This work presents Privateer, the first fully automatic privatization system to handle dynamic and recursive data structures, even in languages with unrestricted pointers. To reduce sensitivity to memory layout, Privateer speculatively separates memory objects. Privateer's lightweight runtime system validates speculative separation and speculative privatization to ensure correct parallel execution. Privateer enables automatic parallelization of general-purpose C/C++ applications, yielding a geomean whole-program speedup of 11.4x over best sequential execution on 24 cores, while non-speculative parallelization yields only 0.93x.
Verifying GPU kernels by test amplification
Authors: Leung Alan , Gupta Manish , Agarwal Yuvraj , Gupta Rajesh , Jhala Ranjit , Lerner Sorin
Published: November 2016

We present a novel technique for verifying properties of data parallel GPU programs via test
amplification
. The key insight behind our work is that we can use the technique of static information flow to amplify the result of a single test execution over the set of all inputs and interleavings that affect the property being verified. We empirically demonstrate the effectiveness of test amplification for verifying race-freedom and determinism over a large number of standard GPU kernels, by showing that the result of verifying a single dynamic execution can be amplified over the massive space of possible data inputs and thread interleavings.
Synthesizing software verifiers from proof rules
Authors: Grebenshchikov Sergey , Lopes Nuno P. , Popeea Corneliu , Rybalchenko Andrey
Published: November 2016

Automatically generated tools can significantly improve programmer productivity. For example, parsers and dataflow analyzers can be automatically generated from declarative specifications in the form of grammars, which tremendously simplifies the task of implementing a compiler. In this paper, we present a method for the automatic synthesis of software verification tools. Our synthesis procedure takes as input a description of the employed proof rule, e.g., program safety checking via inductive invariants, and produces a tool that automatically discovers the auxiliary assertions required by the proof rule, e.g., inductive loop invariants and procedure summaries. We rely on a (standard) representation of proof rules using recursive equations over the auxiliary assertions. The discovery of auxiliary assertions, i.e., solving the equations, is based on an iterative process that extrapolates solutions obtained for finitary unrollings of equations. We show how our method synthesizes automatic safety and liveness verifiers for programs with procedures, multi-threaded programs, and functional programs. Our experimental comparison of the resulting verifiers with existing state-of-the-art verification tools confirms the practicality of the approach.
Inductive data flow graphs
Authors: Farzan Azadeh , Kincaid Zachary , Podelski Andreas
Published: November 2016

The correctness of a sequential program can be shown by the annotation of its control flow graph with inductive assertions. We propose inductive data flow graphs, data flow graphs with incorporated inductive assertions, as the basis of an approach to verifying concurrent programs. An inductive data flow graph accounts for a set of dependencies between program actions in interleaved thread executions, and therefore stands as a representation for the set of concurrent program traces which give rise to these dependencies. The approach first constructs an inductive data flow graph and then checks whether all program traces are represented. The size of the inductive data flow graph is polynomial in the number of data dependencies (in a sense that can be made formal); it does not grow exponentially in the number of threads unless the data dependencies do. The approach shifts the burden of the exponential explosion towards the check whether all program traces are represented, i.e., to a combinatorial problem (over finite graphs).
Abstract conflict driven learning
Authors: D'Silva Vijay , Haller Leopold , Kroening Daniel
Published: November 2016

Modern satisfiability solvers implement an algorithm, called Conflict Driven Clause Learning, which combines search for a model with analysis of conflicts. We show that this algorithm can be generalised to solve the lattice-theoretic problem of determining if an additive transformer on a Boolean lattice is always bottom. Our generalised procedure combines overapproximations of greatest fixed points with underapproximation of least fixed points to obtain more precise results than computing fixed points in isolation. We generalise implication graphs used in satisfiability solvers to derive underapproximate transformers from overapproximate ones. Our generalisation provides a new method for static analysers that operate over non-distributive lattices to reason about properties that require disjunction.
The geometry of types
Authors: Dal lago Ugo , Petit Barbara
Published: November 2016

We show that time complexity analysis of higher-order functional programs can be effectively reduced to an arguably simpler (although computationally equivalent) verification problem, namely checking first-order inequalities for validity. This is done by giving an efficient inference algorithm for linear dependent types which, given a PCF term, produces in output both a linear dependent type and a cost expression for the term, together with a set of proof obligations. Actually, the output type judgement is derivable iff all proof obligations are valid. This, coupled with the already known relative completeness of linear dependent types, ensures that no information is lost, i.e., that there are no false positives or negatives. Moreover, the procedure reflects the difficulty of the original problem: simple PCF terms give rise to sets of proof obligations which are easy to solve. The latter can then be put in a format suitable for automatic or semi-automatic verification by external solvers. Ongoing experimental evaluation has produced encouraging results, which are briefly presented in the paper.
The power of parameterization in coinductive proof
Authors: Hur Chung-Kil , Neis Georg , Dreyer Derek , Vafeiadis Viktor
Published: November 2016

Coinduction is one of the most basic concepts in computer science. It is therefore surprising that the commonly-known lattice-theoretic accounts of the principles underlying coinductive proofs are lacking in two key respects: they do not support compositional reasoning (i.e. breaking proofs into separate pieces that can be developed in isolation), and they do not support incremental reasoning (i.e. developing proofs interactively by starting from the goal and generalizing the coinduction hypothesis repeatedly as necessary).

In this paper, we show how to support coinductive proofs that are both compositional and incremental, using a dead simple construction we call the parameterized greatest fixed point. The basic idea is to parameterize the greatest fixed point of interest over the accumulated knowledge of "the proof so far". While this idea has been proposed before, by Winskel in 1989 and by Moss in 2001, neither of the previous accounts suggests its general applicability to improving the state of the art in interactive coinductive proof.

In addition to presenting the lattice-theoretic foundations of parameterized coinduction, demonstrating its utility on representative examples, and studying its composition with "up-to" techniques, we also explore its mechanization in proof assistants like Coq and Isabelle. Unlike traditional approaches to mechanizing coinduction (e.g. Coq's cofix), which employ syntactic "guardedness checking", parameterized coinduction offers a semantic account of guardedness. This leads to faster and more robust proof development, as we demonstrate using our new Coq library, Paco.
Library abstraction for C/C++ concurrency
Authors: Batty Mark , Dodds Mike , Gotsman Alexey
Published: November 2016

When constructing complex concurrent systems, abstraction is vital: programmers should be able to reason about concurrent libraries in terms of abstract specifications that hide the implementation details. Relaxed memory models present substantial challenges in this respect, as libraries need not provide sequentially consistent abstractions: to avoid unnecessary synchronisation, they may allow clients to observe relaxed memory effects, and library specifications must capture these.

In this paper, we propose a criterion for sound library abstraction in the new C11 and C++11 memory model, generalising the standard sequentially consistent notion of linearizability. We prove that our criterion soundly captures all client-library interactions, both through call and return values, and through the subtle synchronisation effects arising from the memory model. To illustrate our approach, we verify implementations against specifications for the lock-free Treiber stack and a producer-consumer queue. Ours is the first approach to compositional reasoning for concurrent C11/C++11 programs.
Deadlock-freedom-by-design
Authors: Carbone Marco , Montesi Fabrizio
Published: November 2016

Over the last decade, global descriptions have been successfully employed for the verification and implementation of communicating systems, respectively as protocol specifications and choreographies. In this work, we bring these two practices together by proposing a purely-global programming model. We show a novel interpretation of asynchrony and parallelism in a global setting and develop a typing discipline that verifies choreographies against protocol specifications, based on multiparty sessions. Exploiting the nature of global descriptions, our type system defines a new class of deadlock-free concurrent systems (deadlock-freedom-by-design), provides type inference, and supports session mobility. We give a notion of Endpoint Projection (EPP) which generates correct entity code (as pi-calculus terms) from a choreography. Finally, we evaluate our approach by providing a prototype implementation for a concrete programming language and by applying it to some examples from multicore and service-oriented programming.
Synthesis of biological models from mutation experiments
Authors: Koksal Ali Sinan , Pu Yewen , Srivastava Saurabh , Bodik Rastislav , Fisher Jasmin , Piterman Nir
Published: November 2016

Executable biology presents new challenges to formal methods. This paper addresses two problems that cell biologists face when developing formally analyzable models.

First, we show how to automatically synthesize a concurrent in-silico model for cell development given in-vivo experiments of how particular mutations influence the experiment outcome. The problem of synthesis under mutations is unique because mutations may produce non-deterministic outcomes (presumably by introducing races between competing signaling pathways in the cells) and the synthesized model must be able to replay all these outcomes in order to faithfully describe the modeled cellular processes. In contrast, a "regular" concurrent program is correct if it picks any outcome allowed by the non-deterministic specification. We developed synthesis algorithms and synthesized a model of cell fate determination of the earthworm C. elegans. A version of this model previously took systems biologists months to develop.

Second, we address the problem of under-constrained specifications that arise due to incomplete sets of mutation experiments. Under-constrained specifications give rise to distinct models, each explaining the same phenomenon differently. Addressing the ambiguity of specifications corresponds to analyzing the space of plausible models. We develop algorithms for detecting ambiguity in specifications, i.e., whether there exist alternative models that would produce different fates on some unperformed experiment, and for removing redundancy from specifications, i.e., computing minimal non-ambiguous specifications.

Additionally, we develop a modeling language and embed it into Scala. We describe how this language design and embedding allows us to build an efficient synthesizer. For our C. elegans case study, we infer two observationally equivalent models expressing different biological hypotheses through different protein interactions. One of these hypotheses was previously unknown to biologists.
A Content-Aware Video Adaptation Service to Support Mobile Video
Authors: Wilk Stefan , Stohr Denny , Effelsberg Wolfgang
Published: November 2016

Adaptive video streaming systems rely on the availability of different quality versions of a video. Such a system can dynamically adjust the quality of a video stream during its playback depending on the available network throughput. Even if the necessary throughput is available, mobile users can benefit from limiting the generated data traffic as most cellular network contracts have data caps. Usually, if the cap is reached, the throughput is throttled to a speed that does not allow video streaming. Existing systems react to varying network conditions but often neglect content-specific adaptation needs. Content inspection can help to save data traffic when a higher bitrate representation would not increase the perceived quality. In this work, we present the Video Adaptation Service (VAS), a support service for a content-aware video adaptation for mobile devices. Based on the video content, the adaptation process is improved for both the available network resources and the perception of the user. By leveraging the content properties of a video stream, the system is able to maintain a stable video quality and at the same time reduce the generated data traffic. The system is evaluated with different adaptation schemes and shows that content-specific adaptation can both increase the perceived quality as well as reduce the data traffic. Additionally, we demonstrate the practical feasibility of this approach by integrating the VAS into Dynamic Adaptive Streaming over the Hypertext Transfer Protocol.
Processor Design for Soft Errors
Authors: Li Tuo , Ambrose Jude Angelo , Ragel Roshan , Parameswaran Sri
Published: November 2016

Today, soft errors are one of the major design technology challenges at and beyond the 22nm technology nodes. This article introduces the soft error problem from the perspective of processor design. This article also provides a survey of the existing soft error mitigation methods across different levels of design abstraction involved in processor design, including the device level, the circuit level, the architectural level, and the program level.
Transparently Space Sharing a Multicore Among Multiple Processes
Authors: Creech Timothy , Barua Rajeev
Published: November 2016

As hardware becomes increasingly parallel and the availability of scalable parallel software improves, the problem of managing multiple multithreaded applications (processes) becomes important. Malleable processes, which can vary the number of threads used as they run, enable sophisticated and flexible resource management. Although many existing applications parallelized for SMPs with parallel runtimes are in fact already malleable, deployed runtime environments provide no interface nor any strategy for intelligently allocating hardware threads or even preventing oversubscription. Prior research methods either depend on profiling applications ahead of time to make good decisions about allocations or do not account for process efficiency at all, leading to poor performance. None of these prior methods have been adapted widely in practice. This article presents the Scheduling and Allocation with Feedback (SCAF) system: a drop-in runtime solution that supports existing malleable applications in making intelligent allocation decisions based on observed efficiency without any changes to semantics, program modification, offline profiling, or even recompilation. Our existing implementation can control most unmodified OpenMP applications. Other malleable threading libraries can also easily be supported with small modifications without requiring application modification or recompilation.

In this work, we present the SCAF daemon and a SCAF-aware port of the GNU OpenMP runtime. We present a new technique for estimating process efficiency purely at runtime using available hardware counters and demonstrate its effectiveness in aiding allocation decisions.

We evaluated SCAF using NAS NPB parallel benchmarks on five commodity parallel platforms, enumerating architectural features and their effects on our scheme. We measured the benefit of SCAF in terms of sum of speedups improvement (a common metric for multiprogrammed environments) when running all benchmark pairs concurrently compared to equipartitioning—the best existing competing scheme in the literature. We found that SCAF improves on equipartitioning on four out of five machines, showing a mean improvement factor in sum of speedups of 1.04 to 1.11x for benchmark pairs, depending on the machine, and 1.09x on average.

Since we are not aware of any widely available tool for equipartitioning, we also compare SCAF against multiprogramming using unmodified OpenMP, which is the only environment available to end users today. SCAF improves on the unmodified OpenMP runtimes for all five machines, with a mean improvement of 1.08 to 2.07x, depending on the machine, and 1.59x on average.
Abstraction mechanisms for database programming
Authors: Schmidt Joachim W. , Mall Manuel
Published: November 2016

Databases contain vast amounts of highly related data accessed by programs of considerable size and complexity. Therefore, database programming has a particular need for high level constructs that abstract from details of data access, data manipulation, and data control.

The paper investigates the suitability of several well-known abstraction mechanisms for database programming (e.g., control abstraction and functional abstraction). In addition, it presents some new abstraction mechanisms (access abstraction and transactional abstraction) particularly designed to manage typical database problems like integrity and concurrency control.
A programming language framework for designing user interfaces
Authors: Pilote Michel
Published: November 2016

Programming Language researchers increasingly recognize that a high proportion of application development costs involve the interface with users of the application, including various dialogues, input formats, error checking, help and explanation messages, and the like. They also increasingly recognize that maintenance costs tend to overshadow development costs. These two factors even multiply their adverse effects: as the user needs evolve, it is the interface with a system which generally requires the most maintenance. The user relationship is even said to account for about 60 percent of the maintenance problem [Lientz and Swanson 81].

Surprisingly, few programming language constructs are designed to address the area of user interface design. On the contrary, traditional programming language constructs are strongly oriented towards improving programmers' effectiveness in developing the algorithmic and data manipulation aspects of an application. A programmer is basically left to reinvent each time the required procedures to deal with user commands and inputs.