On the Uncontended Complexity of Anonymous Consensus

Consensus is one of the central distributed abstractions. By enabling a collection of processes to agree on one of the values they propose, consensus can be used to implement any generic replicated service in a consistent and fault-tolerant way. In this paper, we study uncontended complexity of anonymous consensus algorithms, counting the number of memory locations used and the number of memory updates performed in operations that encounter no contention. We assume that contention-free operations on a consensus object perform "fast" reads and writes, and resort to more expensive synchronization primitives, such as CAS, only when contention is detected. We call such concurrent implementations interval-solo-fast and derive one of the first nontrivial tight bounds on space complexity of anonymous interval-solo-fast consensus

The Impact of RDMA on Agreement

Remote Direct Memory Access (RDMA) is becoming widely available in data centers. This technology allows a process to directly read and write the memory of a remote host, with a mechanism to control access permissions. In this paper, we study the fundamental power of these capabilities. We consider the well-known problem of achieving consensus despite failures, and find that RDMA can improve the inherent trade-off in distributed computing between failure resilience and performance. Specifically, we show that RDMA allows algorithms that simultaneously achieve high resilience and high performance, while traditional algorithms had to choose one or another. With Byzantine failures, we give an algorithm that only requires $n \geq 2f_P + 1$ processes (where $f_P$ is the maximum number of faulty processes) and decides in two (network) delays in common executions. With crash failures, we give an algorithm that only requires $n \geq f_P + 1$ processes and also decides in two delays. Both algorithms tolerate a minority of memory failures inherent to RDMA, and they provide safety in asynchronous systems and liveness with standard additional assumptions.Comment: Full version of PODC'19 paper, strengthened broadcast algorith

A review on DISC 2005, the 19th International Symposium on Distributed Computing

DISC is an international symposium on the theory, design, analysis, implementation and application of distributed systems and networks. The well-known International Symposium on Distributed Computing is organized annually in cooperation with the European Association for Theoretical Computer Science (EATCS). This is a review on the 19th International Symposium on Distributed Computing, which took place in Kraków, Poland, on September 26--29, 2005. The proceedings of DISC 2005 are published by Springer, as volume 3724 of the Lecture Notes in Computer Science (LNCS) series. The conference website can be found at www.mimuw.edu.pl/~disc2005.Postprint (published version

Making Sense of Learner Performance on Tests of Productive Vocabulary Knowledge

This paper offers a solution to a significant problem for teachers and researchers of language learning that confounds their interpretations and expectations of test data: the apparent simplicity of tests of vocabulary knowledge masks the complexity of the constructs they claim to measure. We first scrutinise task elements in two widely cited productive vocabulary measures, Lex30 (Meara and Fitzpatrick, 2000) and the Lexical Frequency Profile (LFP, Laufer and Nation, 1995), in order to gain a more precise understanding of the relationship between test performance and learner knowledge. Next, in three empirical studies (N = 80, 80, 100) we compare L2 learners’ performance on Lex30, as the static point of reference, with LFP and with two new tests designed to investigate specific elements of the vocabulary test tasks. Correlation analyses indicate systematic differences in the tests’ capacity to capture information about the quality of learners’ word knowledge and the size of their vocabulary resource. Using the findings from this empirical work, we formulate a model of vocabulary ‘capture’ onto which test tasks can be mapped. We demonstrate how capturing key elements of the relationship between test scores and lexical competence can guide teachers and researchers in applying and interpreting vocabulary tests

Emily Dickinson, the Tyrant, and the Daemon: A Critique of Societal Oppression, and the Significance of Artistic Truth

This thesis argues that art, for Dickinson, was an alternative system of salvation which her society could not provide her. Unwilling to surrender herself to the mold of her society, the institutional practice of Christianity and gender expectations, Dickinson chose to take ownership of her life through art, which allowed her to develop a personal language to combat the oppressive forces of the world around her. As a conscious “revolutionist of the word” Dickinson embarked on a path of self-discovery that enabled her to conduct a life in self-imposed exile as a means to emancipate herself from the constraints of conventional living (Howe xi). As Gelpi explains, the normal man can follow the general trend without injury.... but the man who takes to the backstreets and alleys because he cannot endure the broad highway will be the first to discover the psychic elements that are waiting to play their part. (Gelpi 83) Because Dickinson refused to struggle or integrate herself into her society, she enabled herself to fiercely explore her imagination and question the tyranny of institutionalized Christianity, patriarchy, and gender expectations. The commitment she would make to art was not for the sake of an elusive promise of redemption and transcendence of the ‘earthly,’ but rather a temporal goal which sought to uncover the full potential of her humanity as intensely as possible no matter the consequence. As a woman who harnessed and manifested an unnameable gift of language that defied and challenged the people and concepts of her time, Dickinson’s work depicts the struggle between succumbing to the expectations of society and the will to live by the dictates of her imagination

Tools and Language Elements for Testing, Encapsulation and Controlling Abstraction in Large Scale C++ Projects

A disszertáció új kutatási eredményeket mutat be három alapvető szoftver fejlesztési területen: tesztelés, egységbezárás és absztrakció. Az első három tézis az ún. nem-tolakodó teszteléssel foglalkozik, amely egy olyan tesztelési technika amely során nem szükséges semmilyen strukturális módosítást végrehajtanunk a termék forráskódján. Megvitatjuk a már létező nem-tolakodó tesztelési módszereket és felsoroljuk ezek előnyeit és hátrányait. Bevezetünk egy új, nem-tolakodó tesztelési módszert amely függvény hívás közbeavatkozáson alapszik és számos egyértelmű előnnyel rendelkezik a korábbi megoldásokhoz képest. Ezzel az új technikával képesek vagyunk függvényeket teszt dublőrökkel helyettesíteni még akkor is ha azok inline függvények. Továbbá bemutatunk két új kísérleti eljárást amelyek lehetővé teszik, hogy akár típusokat is helyettesítsünk teszt dublőrökkel: az egyik metódus szintaxis fa transzformációkon alapszik, a másik pedig fordítási idejű reflectionön. Demonstráljuk, hogy gyakran előfordul, hogy szükséges privát tagokhoz hozzáférni a nem-tolakodó tesztek esetében. Bemutatunk két új módszert a privát tagok eléréséhez (és ily módon támogatjuk a nem-tolakodó és fehér doboz tesztek létrehozását): egy program könyvtárat amely explicit sablon példányosításon alapszik, illetve az osztályon kívüli barát (friend) nyelvi elemet. Az egységbezárással kapcsolatosan szemléltetjük, hogy bizonyos nyelvi konstrukciók minta C++ barát (friend) túlzottan erős hozzáférést nyújthat egy osztály belső elemeihez. Ez a túlzott hozzáférés hibák forrása lehet az adott szoftverben. Javaslatot teszünk egy új nyelvi elem létrehozására amely lehetővé teszi, hogy megszorítsuk ezt a hozzáférést csupán néhány jól specifikált taghoz, ily módon erősítendő az egységbezárást és adatrejtést. Az egységbezárás mellett az absztrakció a másik alapvető szereplő ha nagy méretű szoftverek fejlesztéséről van szó. Különösen,ha többszálú programokról beszélünk. Bemutatunk egy új magas szintű C++ absztrakciót mely a read-copy-update konkurrens programozási mintán alapszik és elfogadható teljesítményt nyújt amellett, hogy kellően generikus és biztonságos használni. Az itt bemutatott új módszerek mindegyikéhez tartozik prototípus implementáció (ez alól kivételt képez a reflection alapú nem-tolakodó tesztelés ötlete)

Attitudes toward Teaching English in Lebanon: An Exercise in Critical Applied Linguistics

Critical Applied Linguistics (CALx) is both a means of examining the status quo governing the teaching and learning of languages and an opportunity to change or transform existing assumptions and practices. Within the multilingual context of Lebanon, my initial assumption was that English foreign language teachers have not explicitly scrutinized their attitudes to the language they teach or its impact on Arabic (L1). Teacher education and professional development have also not appeared to provide an opportunity to facilitate such a discussion. As such, my study based itself upon the assumption that current teacher education and training have established and reaffirmed mainstream attitudes to the teaching and learning of foreign languages in Lebanon. In order to examine my critical position, my study involved two main phases. Using action research with a mixed methods approach to data collection, the first phase included a survey of 62 English language teachers from different contexts: primary, middle, and high school, in addition to tertiary education. The purpose of this survey was to determine whether teacher attitudes would be mainstream or explicitly critical. In the second phase, I created an intervention in the form of a ‘reflexive practice model’, wherein nine in-service English language teachers, from different contexts as well, would meet to discuss relevant critical themes in the hopes of creating a platform for dialogic inquiry and transformation. Following the model set by Kumaravadivelu (2012), these sessions would value both professional and personal knowledge as participants negotiated their espoused attitudes, with emphasis on the local, ‘lived’, experience. The results of my research showed that teachers, in general, had some mainstream attitudes to the teaching of English, especially the need for early exposure to a foreign language, maximum exposure through English as a medium of instruction, and the monolingual fallacy. They also commonly taught English without reflecting upon any power dynamics or hegemony involved. While most participants agreed that the Arabic language might be suffering because of these practices, they did not believe they had any active role to play in order to preserve L1. However, they were also critical of certain pedagogical practices, especially related to teaching resources and policies that left them feeling powerless and passive. They also mostly believed that their professional development opportunities were insufficient and involved sporadic, expert-led, sessions that were not immediately relevant to their context. From an action research perspective, the ‘reflexive practice model’ was successful as it allowed participants to discuss their assumptions and identity as a whole, creating some immediate change in attitudes and practice, in addition to a feeling of empowerment and hope in a better future. Participants also concluded that such communities of practice would provide in-service teachers with a voice that they could later amplify both within their institutions and beyond, through publishing their findings and participating in conferences in Lebanon that included both ‘experts’ and the practicing teachers. Thus, this ‘reflexive practice model’ can provide an opportunity for continuing – and critical - professional development that also allows participants from different institutions to support one another as they reflect upon their identity and practice