1,996 research outputs found
Fault-tolerant Designs in Lattice Networks on the Klein Bottle
In this note, we consider triangular, square and hexagonal lattices on the flat Klein bottle, and find subgraphs with the property that for any vertices there exists a longest path (cycle) avoiding all of them. This completes work previously done in other lattices
Formal Derivation of Concurrent Garbage Collectors
Concurrent garbage collectors are notoriously difficult to implement
correctly. Previous approaches to the issue of producing correct collectors
have mainly been based on posit-and-prove verification or on the application of
domain-specific templates and transformations. We show how to derive the upper
reaches of a family of concurrent garbage collectors by refinement from a
formal specification, emphasizing the application of domain-independent design
theories and transformations. A key contribution is an extension to the
classical lattice-theoretic fixpoint theorems to account for the dynamics of
concurrent mutation and collection.Comment: 38 pages, 21 figures. The short version of this paper appeared in the
Proceedings of MPC 201
Design of testbed and emulation tools
The research summarized was concerned with the design of testbed and emulation tools suitable to assist in projecting, with reasonable accuracy, the expected performance of highly concurrent computing systems on large, complete applications. Such testbed and emulation tools are intended for the eventual use of those exploring new concurrent system architectures and organizations, either as users or as designers of such systems. While a range of alternatives was considered, a software based set of hierarchical tools was chosen to provide maximum flexibility, to ease in moving to new computers as technology improves and to take advantage of the inherent reliability and availability of commercially available computing systems
Intersection of Longest Paths in Graph Theory and Predicting Performance in Facial Recognition
A set of subsets is said to have the Helly property if the condition that each pair of subsets has a non-empty intersection implies that the intersection of all subsets has a non-empty intersection. In 1966, Gallai noticed that the set of all longest paths of a connected graph is pairwise intersecting and asked if the set had the Helly property. While it is not true in general, a number of classes of graphs have been shown to have the property. In this dissertation, we show that K4-minor-free graphs, interval graphs, circular arc graphs, and the intersection graphs of spider graphs are classes that have this property.
The accuracy of facial recognition algorithms on images taken in controlled conditions has improved significantly over the last two decades. As the focus is turning to more unconstrained or relaxed conditions and toward videos, there is a need to better understand what factors influence performance. If these factors were better understood, it would be easier to predict how well an algorithm will perform when new conditions are introduced.
Previous studies have studied the effect of various factors on the verification rate (VR), but less attention has been paid to the false accept rate (FAR). In this dissertation, we study the effect various factors have on the FAR as well as the correlation between marginal FAR and VR. Using these relationships, we propose two models to predict marginal VR and demonstrate that the models predict better than using the previous global VR
Mixing multi-core CPUs and GPUs for scientific simulation software
Recent technological and economic developments have led to widespread availability of
multi-core CPUs and specialist accelerator processors such as graphical processing units
(GPUs). The accelerated computational performance possible from these devices can be very
high for some applications paradigms. Software languages and systems such as NVIDIA's
CUDA and Khronos consortium's open compute language (OpenCL) support a number of
individual parallel application programming paradigms. To scale up the performance of some
complex systems simulations, a hybrid of multi-core CPUs for coarse-grained parallelism and
very many core GPUs for data parallelism is necessary. We describe our use of hybrid applica-
tions using threading approaches and multi-core CPUs to control independent GPU devices.
We present speed-up data and discuss multi-threading software issues for the applications
level programmer and o er some suggested areas for language development and integration
between coarse-grained and ne-grained multi-thread systems. We discuss results from three
common simulation algorithmic areas including: partial di erential equations; graph cluster
metric calculations and random number generation. We report on programming experiences
and selected performance for these algorithms on: single and multiple GPUs; multi-core CPUs;
a CellBE; and using OpenCL. We discuss programmer usability issues and the outlook and
trends in multi-core programming for scienti c applications developers
Slicing of Concurrent Programs and its Application to Information Flow Control
This thesis presents a practical technique for information flow control for concurrent programs with threads and shared-memory communication. The technique guarantees confidentiality of information with respect to a reasonable attacker model and utilizes program dependence
graphs (PDGs), a language-independent representation of information flow in a program
Dynamic Systolization for Developing Multiprocessor Supercomputers
A dynamic network approach is introduced for developing reconfigurable, systolic arrays or wavefront processors; This allows one to design very powerful and flexible processors to be used in a general-purpose, reconfigurable, and fault-tolerant, multiprocessor computer system. The concepts of macro-dataflow and multitasking can be integrated to handle variable-resolution granularities in computationally intensive algorithms. A multiprocessor architecture, Remps, is proposed based on these design methodologies. The Remps architecture is generalized from the Cedar, HEP, Cray X- MP, Trac, NYU ultracomputer, S-l, Pumps, Chip, and SAM projects. Our goal is to provide a multiprocessor research model for developing design methodologies, multiprocessing and multitasking supports, dynamic systolic/wavefront array processors, interconnection networks, reconfiguration techniques, and performance analysis tools. These system design and operational techniques should be useful to those who are developing or evaluating multiprocessor supercomputers
Eliminating stack overflow by abstract interpretation
ManuscriptAn important correctness criterion for software running on embedded microcontrollers is stack safety: a guarantee that the call stack does not overflow. Our first contribution is a method for statically guaranteeing stack safety of interrupt-driven embedded software using an approach based on context-sensitive dataflow analysis of object code. We have implemented a prototype stack analysis tool that targets software for Atmel AVR microcontrollers and tested it on embedded applications compiled from up to 30,000 lines of C. We experimentally validate the accuracy of the tool, which runs in under 10 sec on the largest programs that we tested. The second contribution of this paper is the development of two novel ways to reduce stack memory requirements of embedded software
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