Scalable Performance Analysis of Massively Parallel Stochastic Systems

The accurate performance analysis of large-scale computer and communication systems is directly inhibited by an exponential growth in the state-space of the underlying Markovian performance model. This is particularly true when considering massively-parallel architectures such as cloud or grid computing infrastructures. Nevertheless, an ability to extract quantitative performance measures such as passage-time distributions from performance models of these systems is critical for providers of these services. Indeed, without such an ability, they remain unable to offer realistic end-to-end service level agreements (SLAs) which they can have any confidence of honouring. Additionally, this must be possible in a short enough period of time to allow many different parameter combinations in a complex system to be tested. If we can achieve this rapid performance analysis goal, it will enable service providers and engineers to determine the cost-optimal behaviour which satisfies the SLAs. In this thesis, we develop a scalable performance analysis framework for the grouped PEPA stochastic process algebra. Our approach is based on the approximation of key model quantities such as means and variances by tractable systems of ordinary differential equations (ODEs). Crucially, the size of these systems of ODEs is independent of the number of interacting entities within the model, making these analysis techniques extremely scalable. The reliability of our approach is directly supported by convergence results and, in some cases, explicit error bounds. We focus on extracting passage-time measures from performance models since these are very commonly the language in which a service level agreement is phrased. We design scalable analysis techniques which can handle passages defined both in terms of entire component populations as well as individual or tagged members of a large population. A precise and straightforward specification of a passage-time service level agreement is as important to the performance engineering process as its evaluation. This is especially true of large and complex models of industrial-scale systems. To address this, we introduce the unified stochastic probe framework. Unified stochastic probes are used to generate a model augmentation which exposes explicitly the SLA measure of interest to the analysis toolkit. In this thesis, we deploy these probes to define many detailed and derived performance measures that can be automatically and directly analysed using rapid ODE techniques. In this way, we tackle applicable problems at many levels of the performance engineering process: from specification and model representation to efficient and scalable analysis

On the reversible extraction of classical information from a quantum source

Consider a source E of pure quantum states with von Neumann entropy S. By the quantum source coding theorem, arbitrarily long strings of signals may be encoded asymptotically into S qubits/signal (the Schumacher limit) in such a way that entire strings may be recovered with arbitrarily high fidelity. Suppose that classical storage is free while quantum storage is expensive and suppose that the states of E do not fall into two or more orthogonal subspaces. We show that if E can be compressed with arbitrarily high fidelity into A qubits/signal plus any amount of auxiliary classical storage then A must still be at least as large as the Schumacher limit S of E. Thus no part of the quantum information content of E can be faithfully replaced by classical information. If the states do fall into orthogonal subspaces then A may be less than S, but only by an amount not exceeding the amount of classical information specifying the subspace for a signal from the source.Comment: 22 pages, Latex2e, journal versio

Structure of states which satisfy strong subadditivity of quantum entropy with equality

We give an explicit characterisation of the quantum states which saturate the strong subadditivity inequality for the von Neumann entropy. By combining a result of Petz characterising the equality case for the monotonicity of relative entropy with a recent theorem by Koashi and Imoto, we show that such states will have the form of a so-called short quantum Markov chain, which in turn implies that two of the systems are independent conditioned on the third, in a physically meaningful sense. This characterisation simultaneously generalises known necessary and sufficient entropic conditions for quantum error correction as well as the conditions for the achievability of the Holevo bound on accessible information.Comment: 9 pages, revtex4. v2 corrects/adds some references and has a bit more discussio

An analysis of the personal-social problems considered important by the junior-high-school adolescent according to sex, age, intelligence quotient and bilingualism

Thesis (Ed.D.)--Boston Universit

Scaling up from greenhouse resistance to fitness in the field for a host of an emerging forest disease.

Forest systems are increasingly threatened by emergent, exotic diseases, yet management strategies for forest trees may be hindered by long generation times and scant background knowledge. We tested whether nursery disease resistance and growth traits have predictive value for the conservation of Notholithocarpus densiflorus, the host most susceptible to sudden oak death. We established three experimental populations to assess nursery growth and resistance to Phytophthora ramorum, and correlations between nursery-derived breeding values with seedling survival in a field disease trial. Estimates of nursery traits' heritability were low to moderate, with lowest estimates for resistance traits. Within the field trial, survival likelihood was increased in larger seedlings and decreased with the development of disease symptoms. The seed-parent family wide likelihood of survival was likewise correlated with family predictors for size and resistance to disease in 2nd year laboratory assays, though not resistance in 1st year leaf assays. We identified traits and seedling families with increased survivorship in planted tanoaks, and a framework to further identify seed parents favored for restoration. The additive genetic variation and seedling disease dynamics we describe hold promise to refine current disease models and expand the understanding of evolutionary dynamics of emergent infectious diseases in highly susceptible hosts

A new tool for the performance analysis of massively parallel computer systems

We present a new tool, GPA, that can generate key performance measures for very large systems. Based on solving systems of ordinary differential equations (ODEs), this method of performance analysis is far more scalable than stochastic simulation. The GPA tool is the first to produce higher moment analysis from differential equation approximation, which is essential, in many cases, to obtain an accurate performance prediction. We identify so-called switch points as the source of error in the ODE approximation. We investigate the switch point behaviour in several large models and observe that as the scale of the model is increased, in general the ODE performance prediction improves in accuracy. In the case of the variance measure, we are able to justify theoretically that in the limit of model scale, the ODE approximation can be expected to tend to the actual variance of the model

Supporting siblings of children with a special educational need or disability : an evaluation of Sibs Talk, a one‐to‐one intervention delivered by staff in mainstream schools

A group often overlooked for specific supports in schools are siblings of children with a disability, special educational needs or a serious long‐term condition (SEND). In this article we review the current sibling research and identify a lack of literature on interventions, particularly within a school context. We then present a description of Sibs Talk, an example of a new school‐based intervention to support siblings. Sibs Talk is a ten‐session, one‐to‐one intervention approach for schools to complete with Key Stage 2 children who have a brother or sister with SEND. Finally, we present an initial evaluation of the effectiveness of Sibs Talk, using a pre and post evaluation format with a sample of 55 children from 11 schools. The data presented in this evaluation indicate that Sibs Talk may have contributed to positive outcomes for participating children

Neuroendocrine and Behavioral Responses to Stress in Hypothyroidism

A positive relationship has been discovered linking heightened ACTH levels in the pituitary to increased hypothyroidism rates, suggesting that stress negatively impacts thyroid functioning. Hypothyroidism is frequently misdiagnosed and treated as depression, yet little is known about this relationship. Nine C57BL/6J subjects were given 0.25% 6-propyl-2-thiouracil per gram for two weeks and twenty-nine were kept on a standard laboratory diet prior to tail suspension testing. The control group was further divided into six-day, single day, and no tail suspension testing. Following the final trail all groups were scored behaviorally in on the open field test. Serum samples were then acquired and T4 levels were calculated. Thyroid status was significantly different between euthyroid (9.87 μg/dL) and hypothyroid (5.50 μg/dL) treatment groups (t (18)=4.57, p\u3c .01). The single day-TST group had significantly greater total activity (t (18) = 2.721, p \u3c .05) and activity \u3e2 volts (t (18) = 2. 886, p \u3c .05) than the six day-TST group. Also, open field behavioral testing showed that single day-TST and hypothyroid groups had less overall movement and more depressed behaviors. These results indicate that low stress and hypothyroidism tend to trigger the symptoms of major depression, but as the stress level increases the symptoms of depression tend to develop into an anxiety disorder. These data have important implications for the treatment of stress-induced affective disorders

Plan of the Southerly and Westerly Part of the Town of Edmunds

Plan of the south-westerly part of the town of Edmunds, particularly the land in dispute between Aaron and Benjamin Hobart. The Hobart dispute encompassed a total of 134 1/4 acres along the length of the 6th Range. The disputed lines are labeled J-E and G-F. The map scale is 1:15,840 or 80 rods per inch.https://digitalcommons.library.umaine.edu/mainebicentennial/1042/thumbnail.jp

Modernity Contextualises New Zealand's Royal Commission on Genetic Modification: A Discourse Analysis

The New Zealand's Royal Commission on Genetic Modification (RCGM)'s report was released in the year 2001. RCGM's findings supports the ongoing development of genetic engineering in New Zealand and recommends the recommencement of genetic modification field trials