Lower bounds on systolic gossip

AbstractGossiping is an extensively investigated information dissemination process in which each processor has a distinct item of information and has to collect all the items possessed by the other processors. In this paper we provide an innovative and general lower bound technique relying on the novel notion of delay digraph of a gossiping protocol and on the use of matrix norm methods. Such a technique is very powerful and allows the determination of new and significantly improved lower bounds in many cases. In fact, we derive the first general lower bound on the gossiping time of systolic protocols, i.e., constituted by a periodic repetition of simple communication steps. In particular, given any network of n processors and any systolic period s, in the directed and the undirected half-duplex cases every s-systolic gossip protocol takes at least log(n)/log(1/λ)−O(loglog(n)) time steps, where λ is the unique solution between 0 and 1 of λ·p⌊s/2⌋(λ)·p⌈s/2⌉(λ)=1, with pi(λ)=1+λ2+⋯+λ2i−2 for any integer i>0. We then provide improved lower bounds in the directed and half-duplex cases for many well-known network topologies, such as Butterfly, de Bruijn, and Kautz graphs. All the results are extended also to the full-duplex case. Our technique is very general, as for s→∞ it allows the determination of improved results even for non-systolic protocols. In fact, for general networks, as a simple corollary it yields a lower bound only an O(loglog(n)) additive factor far from the general one independently proved in [Proc. 1st ACM Symposium on Parallel Algorithms and Architectures (SPAA), 1989, p. 318; Topics in Combinatorics and Graph Theory (1990) 451; SIAM Journal on Computing 21(1) (1992) 111; Discrete Applied Mathematics 42 (1993) 75] for all graphs and any (non-systolic) gossip protocol. Moreover, for specific networks, it significantly improves with respect to the previously known results, even in the full-duplex case. Correspondingly, better lower bounds on the gossiping time of non-systolic protocols are determined in the directed, half-duplex and full-duplex cases for Butterfly, de Bruijn, and Kautz graphs. Even if in this paper we give only a limited number of examples, our technique has wide applicability and gives a general framework that often allows to get improved lower bounds on the gossiping time of systolic and non-systolic protocols in the directed, half-duplex and full-duplex cases

Engineering Resilient Collective Adaptive Systems by Self-Stabilisation

Collective adaptive systems are an emerging class of networked computational systems, particularly suited in application domains such as smart cities, complex sensor networks, and the Internet of Things. These systems tend to feature large scale, heterogeneity of communication model (including opportunistic peer-to-peer wireless interaction), and require inherent self-adaptiveness properties to address unforeseen changes in operating conditions. In this context, it is extremely difficult (if not seemingly intractable) to engineer reusable pieces of distributed behaviour so as to make them provably correct and smoothly composable. Building on the field calculus, a computational model (and associated toolchain) capturing the notion of aggregate network-level computation, we address this problem with an engineering methodology coupling formal theory and computer simulation. On the one hand, functional properties are addressed by identifying the largest-to-date field calculus fragment generating self-stabilising behaviour, guaranteed to eventually attain a correct and stable final state despite any transient perturbation in state or topology, and including highly reusable building blocks for information spreading, aggregation, and time evolution. On the other hand, dynamical properties are addressed by simulation, empirically evaluating the different performances that can be obtained by switching between implementations of building blocks with provably equivalent functional properties. Overall, our methodology sheds light on how to identify core building blocks of collective behaviour, and how to select implementations that improve system performance while leaving overall system function and resiliency properties unchanged.Comment: To appear on ACM Transactions on Modeling and Computer Simulatio

The Role of Place in Malcolm Cowley\u27s Blue Juniata and Exile\u27s Return

This study examines the various ways in which Malcolm Cowley develops and uses sense of place in his works Blue Juniata: Collected Poems and Exile\u27s Return. Through examination of the literature, I identify four phases of place sense. Starting with childhood in the Identification phase, I illustrate the development of Cowley\u27s place perspective through his poems and writings. As he moves through Adventure and Exile phases, I discuss their relation to the Identification phase and to each other. Likewise, I consider the role of the Nostalgia phase as a bridge from literary to experiential perception. Through close examination of his writing, I define the identifying features of each phase as well as their relationship to other phases. Further, I examine Cowley\u27s use of phases of place perception. One use is generational identification, allowing Cowley to differentiate his literary generation from those coming both before and after. Similar to this idea is the use of place perception to identify a certain time period. By linking place and ideology, Cowley metonymically references a certain set of experiences. The role of place perception as a metonymic identifier is drawn from the idea that place perception serves as a guide to background knowledge for the reader. An important aspect of its use as a guide is the establishment of common experience between Cowley and his audience. Finally, I explain the use of place perception as a mechanism for developing story. While I include Cowley\u27s own ideas concerning generations and the cycle of Adventure and Exile, the main assertion of my investigation is that he presents four distinct phases of place perception. Also, this study presents various ways in which Cowley uses place perception as an organizing theme in his works. Further, while he describes many of his experiences as attempts to disassociate from place, place perception is, paradoxically, at all times central to his thinking. Cowley uses various aspects of place and place perception in such a way that his own ideas of identity are inextricably tied to it. Ultimately, his life, as presented through his literature, illustrates the passage from naive childhood to nostalgic reflection

Engineering Self-Adaptive Collective Processes for Cyber-Physical Ecosystems

The pervasiveness of computing and networking is creating significant opportunities for building valuable socio-technical systems. However, the scale, density, heterogeneity, interdependence, and QoS constraints of many target systems pose severe operational and engineering challenges. Beyond individual smart devices, cyber-physical collectives can provide services or solve complex problems by leveraging a “system effect” while coordinating and adapting to context or environment change. Understanding and building systems exhibiting collective intelligence and autonomic capabilities represent a prominent research goal, partly covered, e.g., by the field of collective adaptive systems. Therefore, drawing inspiration from and building on the long-time research activity on coordination, multi-agent systems, autonomic/self-* systems, spatial computing, and especially on the recent aggregate computing paradigm, this thesis investigates concepts, methods, and tools for the engineering of possibly large-scale, heterogeneous ensembles of situated components that should be able to operate, adapt and self-organise in a decentralised fashion. The primary contribution of this thesis consists of four main parts. First, we define and implement an aggregate programming language (ScaFi), internal to the mainstream Scala programming language, for describing collective adaptive behaviour, based on field calculi. Second, we conceive of a “dynamic collective computation” abstraction, also called aggregate process, formalised by an extension to the field calculus, and implemented in ScaFi. Third, we characterise and provide a proof-of-concept implementation of a middleware for aggregate computing that enables the development of aggregate systems according to multiple architectural styles. Fourth, we apply and evaluate aggregate computing techniques to edge computing scenarios, and characterise a design pattern, called Self-organising Coordination Regions (SCR), that supports adjustable, decentralised decision-making and activity in dynamic environments.Con lo sviluppo di informatica e intelligenza artificiale, la diffusione pervasiva di device computazionali e la crescente interconnessione tra elementi fisici e digitali, emergono innumerevoli opportunità per la costruzione di sistemi socio-tecnici di nuova generazione. Tuttavia, l'ingegneria di tali sistemi presenta notevoli sfide, data la loro complessità—si pensi ai livelli, scale, eterogeneità, e interdipendenze coinvolti. Oltre a dispositivi smart individuali, collettivi cyber-fisici possono fornire servizi o risolvere problemi complessi con un “effetto sistema” che emerge dalla coordinazione e l'adattamento di componenti fra loro, l'ambiente e il contesto. Comprendere e costruire sistemi in grado di esibire intelligenza collettiva e capacità autonomiche è un importante problema di ricerca studiato, ad esempio, nel campo dei sistemi collettivi adattativi. Perciò, traendo ispirazione e partendo dall'attività di ricerca su coordinazione, sistemi multiagente e self-*, modelli di computazione spazio-temporali e, specialmente, sul recente paradigma di programmazione aggregata, questa tesi tratta concetti, metodi, e strumenti per l'ingegneria di ensemble di elementi situati eterogenei che devono essere in grado di lavorare, adattarsi, e auto-organizzarsi in modo decentralizzato. Il contributo di questa tesi consiste in quattro parti principali. In primo luogo, viene definito e implementato un linguaggio di programmazione aggregata (ScaFi), interno al linguaggio Scala, per descrivere comportamenti collettivi e adattativi secondo l'approccio dei campi computazionali. In secondo luogo, si propone e caratterizza l'astrazione di processo aggregato per rappresentare computazioni collettive dinamiche concorrenti, formalizzata come estensione al field calculus e implementata in ScaFi. Inoltre, si analizza e implementa un prototipo di middleware per sistemi aggregati, in grado di supportare più stili architetturali. Infine, si applicano e valutano tecniche di programmazione aggregata in scenari di edge computing, e si propone un pattern, Self-Organising Coordination Regions, per supportare, in modo decentralizzato, attività decisionali e di regolazione in ambienti dinamici

Outcasts of the Universe: Shyness in Hawthorne and James

In Outcasts of the Universe, I argue that shyness is a modern dilemma, problematized by the broader shifts in American society: the expanding marketplace, the idealization of the self-made man, the rise of feminism and ever-changing gender roles, and a slow consolidation of the bachelor, the artist, and the aesthete into the stigmatized figure of the homosexual. By drawing on both the lives and works of Hawthorne and James, I theorize shyness as an alternative model of social and sexual engagement in the nineteenth century. In particular, I adapt the queer theory concept of closetedness, a concept that has no equivalent in heterosexual terms--unless it is shyness itself. In doing so, I contribute new insights to the fields of gender studies and to queer theory, both by expanding theories of the closet to heterosexual narratives and by exploring how closetedness might be psychologically overdetermined by shyness, melancholy, and introversion

From distributed coordination to field calculus and aggregate computing

open6siThis work has been partially supported by: EU Horizon 2020 project HyVar (www.hyvar-project .eu), GA No. 644298; ICT COST Action IC1402 ARVI (www.cost -arvi .eu); Ateneo/CSP D16D15000360005 project RunVar (runvar-project.di.unito.it).Aggregate computing is an emerging approach to the engineering of complex coordination for distributed systems, based on viewing system interactions in terms of information propagating through collectives of devices, rather than in terms of individual devices and their interaction with their peers and environment. The foundation of this approach is the distillation of a number of prior approaches, both formal and pragmatic, proposed under the umbrella of field-based coordination, and culminating into the field calculus, a universal functional programming model for the specification and composition of collective behaviours with equivalent local and aggregate semantics. This foundation has been elaborated into a layered approach to engineering coordination of complex distributed systems, building up to pragmatic applications through intermediate layers encompassing reusable libraries of program components. Furthermore, some of these components are formally shown to satisfy formal properties like self-stabilisation, which transfer to whole application services by functional composition. In this survey, we trace the development and antecedents of field calculus, review the field calculus itself and the current state of aggregate computing theory and practice, and discuss a roadmap of current research directions with implications for the development of a broad range of distributed systems.embargoed_20210910Viroli, Mirko; Beal, Jacob; Damiani, Ferruccio; Audrito, Giorgio; Casadei, Roberto; Pianini, DaniloViroli, Mirko; Beal, Jacob; Damiani, Ferruccio; Audrito, Giorgio; Casadei, Roberto; Pianini, Danil

Clergy stress, complex trauma and Sabbath practice : a study on Sabbath practice as healing process for clergy serving in stressful appointments

https://place.asburyseminary.edu/ecommonsatsdissertations/1849/thumbnail.jp

Firefighters, hostility, and satisfaction with life, job and marital relationship

Hostility is associated with negative health outcomes. Empirical research has indicated that high levels of hostility, in association with personal characteristics, may result in either aggressive actions and re-actions, or isolation and disengagement. The purpose of this study was to investigate hostility and its influence on mental health, overall satisfaction with life, job, and marital relationship, and cardiovascular health of professional firefighters. The study was analyzed in the context of Social Ecology Theory exploring how personality, spousal relationship, and social factors influenced the relationship between work and health. Firefighters were invited to engage their romantic partners in the study assessing how work stress impacted intimate relationship. Data analyses involved structural equation modeling, as well as repeated measures multivariate analysis of variance and multilinear regressions. The results indicated that work stress and exposure to toxic environment and hazardous conditions have a negative impact on the mental health and overall satisfaction of firefighters, but not on hostility. When controlling for personality, openness to experience revealed a significant relationship between work and hostility. No significant relationships were observed either between hostility and domestic conflict or between hostility and cardiovascular health.hostilitynegative health outcomesempirical researchassociation with personal characteristicsinfluence on mental healthSocial Ecology Theor