Dissertation Defense

Measuring and Characterizing Properties of Peer-To-Peer Systems

Peer-to-peer systems are becoming increasingly popular, with millions of simultaneous users and a wide range of applications. Understanding existing systems and devising new peer-to-peer techniques relies on access to representative models, derived from empirical observations, of user behavior and peer-to-peer system behavior on a real network. However, it is challenging to accurately capture behavior in peer-to-peer systems because they are distributed, large, and rapidly changing.

Deconstructing phylogenetic reconstruction: Effects of assumption violations on evolutionary inference

Knowing how organisms are related evolutionarily is crucial for interpreting nearly all biological results. Evolutionary history is inferred using computational techniques that make simplifying assumptions about the evolutionary process. There is ample biological evidence that many of these assumptions are routinely violated, but little is known about the effects of assumption violations on phylogenetic inference.

Cheat-Proof and Scalable Event Ordering for Massively Multiplayer Online Games

Real-time, interactive, multi-user (RIM) applications are networked applications that allow users to collaborate and interact with each other over the Internet for work, education and training, or entertainment purposes. Multiplayer games, distance learning applications, collaborative whiteboards, immersive educational and training simulations, and distributed interactive simulations are examples of these applications. Of these RIM applications, multiplayer games are an important class for research due to their widespread deployment and popularity on the Internet.

Model-based Automatic Performance Diagnosis of Parallel Computations

Scientific parallel programs often undergo significant performance tuning before meeting their performance expectation. Performance tuning naturally involves a diagnosis process -- locating performance bugs that make a program inefficient and explaining them in terms of high-level program design. Important performance measurement and analysis tools have been developed to support the performance analysis with the facilities of running experiments on parallel computers and generating measurement data to evaluate performance.

Neuroanatomical segmentation in MRI exploiting a priori knowledge

Neuroanatomical segmentation is a problem of extraction of a description of particular neuroanatomical structures of interest that reflects the morphometry (shape measurements) of the subject's neuroanatomy from any image rendering the neuroanatomical structures of the subject. This dissertation presents a set of algorithms for automatic extraction of cerebral white mater (WM) and gray matter (GM) as well as reconstruction of cortical surfaces from T1-weighted MR images.

Intermediate Language Design in Optimizing Compilers

Every compiler passes code through several stages, each a sort of
mini-compiler of its own. Thus each stage may deal with the code in a
different representation, which may have little to do with the source or
target language. We can describe these in-memory representations as languages
in their own right, which we call \emph{intermediate languages}.

This dissertation explores the connections between different intermediate
languages and how they can be interderived, then demonstrates how translation

Wavelet Compression for High Performance Computing

As HPC systems move towards exascale, the discrepancy between computational power and I/O transfer rate is only growing larger. Lossy in situ compression is a promising solution to address this gap, since it alleviates I/O constraints while still enabling traditional post hoc analysis. This thesis explores the viability of such a solution with respect to a specific kind of compressor — wavelets.

Properties of Sequent-Calculus-Based Languages

Programmers don't just have to write programs, they are have to reason about them. Programming languages aren't just tools for instructing computers what to do, they are tools for reasoning. And, it isn't just programmers who reason about programs: compilers and other tools reason similarly as they transform from one language into another one, or as they optimize an inefficient program into a better

Gait Animation and Analysis for Biomechanically-Articulated Skeletons

Digital three-dimensional (3D) models are useful for biomechanical analysis because they can be interactively visualized and manipulated. Synthesizing and analyzing animal locomotion with these models, however, is difficult due to the large number of joints in a fully articulated skeleton, the complexity of the individual joints, and the huge space of possible configurations, or poses, of the skeleton taken as a whole. A joint may be capable of several biological movements, each represented by a degree of freedom (DOF).

Framework-based Model Construction with AOP assistance

I am part of a group that is building software for smart homes using a Java framework called Open Service Gateway Initiative (OSGi). Our concern is with proving certain properties correct about the framework and any application built on top of it. I have found it useful to take a model-checking approach to the proof problem. In recognition of the commonality of OSGi applications, I believe it is possible to build a modeling framework parallel to the OSGi specification to ease the model construction for OSGi applications.

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