VerifyThis 2019: a program verification competition

VerifyThis is a series of program verification competitions that emphasize the human aspect: participants tackle the verification of detailed behavioral properties—something that lies beyond the capabilities of fully automatic verification and requires instead human expertise to suitably encode programs, specifications, and invariants. This paper describes the 8th edition of VerifyThis, which took place at ETAPS 2019 in Prague. Thirteen teams entered the competition, which consisted of three verification challenges and spanned 2 days of work. This report analyzes how the participating teams fared on these challenges, reflects on what makes a verification challenge more or less suitable for the typical VerifyThis participants, and outlines the difficulties of comparing the work of teams using wildly different verification approaches in a competition focused on the human aspect.

     

Fuzzy CoCo: a cooperative-coevolutionary approach to fuzzy modeling

Co-evolutionary algorithms have received increased attention in the past few years within the domain of evolutionary computation. In this paper, we combine the search power of co-evolutionary computation with the expressive power of fuzzy systems, and introduce a novel algorithm, called Fuzzy CoCo (fuzzy cooperative coevolution). We demonstrate the efficacy of Fuzzy CoCo by applying it to a hard, real-world problem - breast cancer diagnosis, obtaining the best results to date while expending less computational effort than previous processes. Analyzing our results, we derive guidelines for setting the algorithm parameters given a (hard) problem to solve. We hope Fuzzy CoCo proves to be a powerful tool in the fuzzy modeler toolkit     

Student cluster competition: ParConnect reproducibility task report

Reproducibility is a desirable characteristic of any experimental work in computer science. In this paper, we reproduce the results in the paper, “A parallel connectivity algorithm for de Bruijn graphs in metagenomic applications”, for verifying their claims on the speed and scalability of their algorithm. We first state the claims made in the original paper. Then, we describe our hardware and software setup used for the reproducibility task, followed by the steps taken to setup the proposed algorithm and profiling software. Lastly, we present the results obtained from our experiments and show that we are able to reproduce most of the claims made in the original paper.     

Some Results on the Confluence Property of Combined Term Rewriting Systems

Generally speaking,confluence property is not preserved when Term Rewriting Systems (TRSs) are combined,even if they are canonical.In this paper we give some sufficient conditions for ensuring the confluence property of combined left-linear,overlapping TRSs.     

On the confluence of lambda-calculus with conditional rewriting

The confluence of untyped λ-calculus with unconditional rewriting is now well un- derstood. In this paper, we investigate the confluence of λ-calculus with conditional rewriting and provide general results in two directions.First, when conditional rules are algebraic. This extends results of Müller and Dougherty for unconditional rewriting. Two cases are considered, whether β-reduction is allowed or not in the evaluation of conditions. Moreover, Dougherty’s result is improved from the assumption of strongly normalizing β-reduction to weakly normalizing β-reduction. We also provide examples showing that outside these conditions, modularity of confluence is difficult to achieve.Second, we go beyond the algebraic framework and get new confluence results using a restricted notion of orthogonality that takes advantage of the conditional part of rewrite rules.     

On quasi orders of words and the confluence property

We investigate the confluence property, that is, the property of a language to contain, for any two words of it, one which is bigger, with respect to a given quasi order on the respective free monoid, than each of the former two. This property is investigated mainly for regular and context-free languages. As a consequence of our study, we give an answer to an old open problem raised by Haines concerning the effective regularity of the sets of subwords. Namely, we prove that there are families with a decidable emptiness problem for which the regularity of the sets of subwords is not effective.     

A direct proof of the confluence of combinatory strong reduction

I give a proof of the confluence of combinatory strong reduction that does not use the one of λ$\lambda$-calculus. I also give simple and direct proofs of a standardization theorem for this reduction and the strong normalization of simply typed terms.     

MRx design and criticism: the confluence of media studies,performance and social interaction

Abstract

In this article, we bring together the lenses of media studies, performance studies and social interaction offered in the other essays in this special issue and discuss their collective contribution towards a more nuanced understanding of MR^x. We illustrate this capacity by a brief critical review of a recent MR^x environment: Mégaphone. We suggest how the lenses can also contribute to a design vocabulary for future MR^x experiences.     

On deciding the confluence of a finite string-rewriting system on a given congruence class

In general it is undecidable whether or not a given finite string-rewriting system R is confluent on a given congruence class [w]_R, even when only length-reducing systems are considered. However, for finite monadic string-rewriting systems this problem becomes decidable in double exponential time. For certain subclasses of monadic string-rewriting systems algorithms of lower complexity are obtained for solving this problem.     

Winsocking the competition

Users are throwing bricks at Microsoft for nuking other companies' WINSOCK.DLL entries in Win 95. Users gripe that when they access Internet via either Win 95's MSN (Microsoft Network) or its remote access features, their WINSOCK.DLL file is renamed WINSOCK.OLD. Microsoft then writes in a new WINSOCK.DLL that permits use only of Microsoft's MSN software. Unless a Internet-using program can access WINSOCK.DLL, the program cannot get to the Net. For example, use MSN once and Netscape is unusable after that, because it cannot fire up without accessing WINSOCK, and it can't do that any more. Even one test run on MSN automatically kills any Net browser competitive with MSN. The user is therefore wed to MSN for any access to the Net, and divorce from MSN is tough to make stick. The only way to beat the problem is to use a special Win 95 version of the competitive program, and they are mostly not yet on the market. Is this tactic legal? The facts surrounding the MSN Net browser issue are not completely clear. Conceivably, this is, as Microsoft claim just a technology problem. The author looks at this issue     

Influence of adjusting the inlet channel confluence angle on mixing behaviour in inertial microfluidic mixers

Recent drive for high-throughput microfluidic systems has triggered tremendous research effort to develop efficient, high-throughput microfluidic mixers. In particular, inducing a fluid–fluid collision at high flow rate in microfluidic channel has been suggested as an effective strategy to enhance mixing. However, previous studies using T-shaped microfluidic mixers showed that, in addition to fluid–fluid collision, the confluence angle of fluid stream in microfluidic channel also has a dramatic effect on mixing. This study suggests the possibility to enhance mixing by simply changing the inlet confluence angle of the streams. In this work, we assess the mixing behaviour of microfluidic mixers with variable inlet confluence angle with the Reynolds number (Re) range of 2.83–566. It is shown that the increase in inlet confluence angle enables the reduction of Re required for complete mixing. Simulation results demonstrate that increasing the confluence angle facilitates the interaction of vortices in mixers to induce an enhanced mixing. We further demonstrate that the increased interaction of vortices also prompts the turbulent emulsification where a significant reduction in emulsion size is observed for each mixer with increased inlet confluence angle at same Re.     

基于CUDA的汇流分析并行算法的研究与实现*

针对基于数字高程模型（DEM）生成流域等流时线的快速运算问题,提出了一种基于统一设备计算架构（CUDA）平台同时可发挥图形处理器（GPU）并行运算特性的汇流分析的快速并行算法。采用改进后的归并排序算法进行数据排序及新的内存分配策略和改进的并行算法进行汇流分析。用该并行算法和CPU上的串行算法, 对生成基于DEM的等流时线运算时间和矩阵乘法运算时间进行分析验证。实验结果表明,基于CUDA的汇流分析并行算法能提高系统的计算效率,具有较好的效果。     

FVC2000: fingerprint verification competition

Reliable and accurate fingerprint recognition is a challenging pattern recognition problem, requiring algorithms robust in many contexts. FVC2000 competition attempted to establish the first common benchmark, allowing companies and academic institutions to unambiguously compare performance and track improvements in their fingerprint recognition algorithms. Three databases were created using different state-of-the-art sensors and a fourth database was artificially generated; 11 algorithms were extensively tested on the four data sets. We believe that FVC2000 protocol, databases, and results will be useful to all practitioners in the field not only as a benchmark for improving methods, but also for enabling an unbiased evaluation of algorithms     

Confidence and competition online: ESL student perspectives on web-based discussions in the classroom

English as a Second Language (ESL) students bring a diverse array of perspectives on language learning that inform how they negotiate different kinds of spaces in the university writing classroom. This study addresses the variance in how three different ESL students participated in web-based discussion boards and chat rooms in their first-year university writing course. Documenting students’ perceptions of technology provided pedagogical insight into how students took up or dismissed particular kinds of web-based writing. This study found that individual students made choices in their web-based writing in ways that reflected their previous experiences with technology and writing, their views of themselves as students and writers, and their relative comfort level with their peers in the classroom. However, their choices were also constrained by the pedagogical structure of the course, including the centrality of the instructor and the institutional directive for individualized assessment.     

Datalink controls and LSI circuits—the confluence of architecture and technology

Datalink control chips (DLCCs) will simplify the implementation of data-communications and control procedures. The use of protocols and the field of datalink controls in general are surveyed. The possible role for DLCCs within micro-computer systems are described.