Physical Sciences and Mathematics Commons^™

High Quality Alias Free Image Rotation, Charles B. Owen, Fillia Makedon

Dartmouth Scholarship

This paper presents new algorithms for the rotation of images. The primary design criteria for these algorithms is very high quality. Common methods for image rotation, including convolutional and separable approaches, are examined and shown to exhibit significant high frequency aliasing problems. A new resampling filter design methodology is presented which minimizes the problem for conventional convolution-based image rotation. The paper also presents a new separable image rotation algorithm which exhibits improved performance in term of reduction in artifacts and an efficient $O(N^{2} log N)$ running time.

File-Access Characteristics Of Parallel Scientific Workloads, Nils Nieuwejaar, David Kotz, Apratim Purakayastha, Carla Schlatter Ellis, Michael L. Best

Dartmouth Scholarship

Phenomenal improvements in the computational performance of multiprocessors have not been matched by comparable gains in I/O system performance. This imbalance has resulted in I/O becoming a significant bottleneck for many scientific applications. One key to overcoming this bottleneck is improving the performance of multiprocessor file systems. \par The design of a high-performance multiprocessor file system requires a comprehensive understanding of the expected workload. Unfortunately, until recently, no general workload studies of multiprocessor file systems have been conducted. The goal of the CHARISMA project was to remedy this problem by characterizing the behavior of several production workloads, on different machines, …

Flexibility And Performance Of Parallel File Systems, David Kotz, Nils Nieuwejaar

Dartmouth Scholarship

As we gain experience with parallel file systems, it becomes increasingly clear that a single solution does not suit all applications. For example, it appears to be impossible to find a single appropriate interface, caching policy, file structure, or disk-management strategy. Furthermore, the proliferation of file-system interfaces and abstractions make applications difficult to port. \par We propose that the traditional functionality of parallel file systems be separated into two components: a fixed core that is standard on all platforms, encapsulating only primitive abstractions and interfaces, and a set of high-level libraries to provide a variety of abstractions and application-programmer interfaces …

Transportable Agents Support Worldwide Applications, David Kotz, Robert Gray, Daniela Rus

Dartmouth Scholarship

Worldwide applications exist in an environment that is inherently distributed, dynamic, heterogeneous, insecure, unreliable, and unpredictable. In particular, the latency and bandwidth of network connections varies tremendously from place to place and time to time, particularly when considering wireless networks, mobile devices, and satellite connections. Applications in this environment must be able to adapt to different and changing conditions. We believe that transportable autonomous agents provide an excellent mechanism for the construction of such applications. We describe our prototype transportable-agent system and several applications.

Worldwide applications exist in an environment that is inherently distributed, dynamic, heterogeneous, insecure, unreliable, and unpredictable. …

Determining An Out-Of-Core Fft Decomposition Strategy For Parallel Disks By Dynamic Programming, Thomas H. Cormen

Dartmouth Scholarship

We present an out-of-core FFT algorithm based on the in-core FFT method developed by Swarztrauber. Our algorithm uses a recursive divide-and-conquer strategy, and each stage in the recursion presents several possibilities for how to split the problem into subproblems. We give a recurrence for the algorithm's I/O complexity on the Parallel Disk Model and show how to use dynamic programming to determine optimal splits at each recursive stage. The algorithm to determine the optimal splits takes only Theta(lg^2 N) time for an N-point FFT, and it is practical. The out-of-core FFT algorithm itself takes considerably longer.

Autonomous And Adaptive Agents That Gather Information, Daniela Rus, Robert Gray, David Kotz

Dartmouth Scholarship

We have designed and implemented autonomous software agents. Autonomous software agents navigate independently through a heterogeneous network of computers. They can sense the state of the network, monitor software conditions, and interact with other agents. The network-sensing tools allow our agents to adapt to the network configuration and to navigate under the control of reactive plans. In this paper we illustrate the intelligent and adaptive behavior of autonomous agents in distributed information-gathering tasks.

The Expected Lifetime Of Single-Address-Space Operating Systems, David Kotz, Preston Crow

Dartmouth Scholarship

Trends toward shared-memory programming paradigms, large (64-bit) address spaces, and memory-mapped files have led some to propose the use of a single virtual-address space, shared by all processes and processors. To simplify address-space management, some have claimed that a 64-bit address space is sufficiently large that there is no need to ever re-use addresses. Unfortunately, there has been no data to either support or refute these claims, or to aid in the design of appropriate address-space management policies. In this paper, we present the results of extensive kernel-level tracing of the workstations on our campus, and discuss the implications for …

Low-Degree Spanning Trees Of Small Weight, Samir Khuller, Balaji Raghavachari, Neal Young

Dartmouth Scholarship

Given n points in the plane, the degree-K spanning-tree problem asks for a spanning tree of minimum weight in which the degree of each vertex is at most K. This paper addresses the problem of computing low-weight degree-K spanning trees for $K > 2$. It is shown that for an arbitrary collection of n points in the plane, there exists a spanning tree of degree 3 whose weight is at most 1.5 times the weight of a minimum spanning tree. It is shown that there exists a spanning tree of degree 4 whose weight is at most 1.25 times …

Flexibility And Performance Of Parallel File Systems, David Kotz, Nils Nieuwejaar

Dartmouth Scholarship

Many scientific applications for high-performance multiprocessors have tremendous I/O requirements. As a result, the I/O system is often the limiting factor of application performance. Several new parallel file systems have been developed in recent years, each promising better performance for some class of parallel applications. As we gain experience with parallel computing, and parallel file systems in particular, it becomes increasingly clear that a single solution does not suit all applications. For example, it appears to be impossible to find a single appropriate interface, caching policy, file structure, or disk management strategy. Furthermore, the proliferation of file-system interfaces and abstractions …

Introduction To Multiprocessor I/O Architecture, David Kotz

Dartmouth Scholarship

The computational performance of multiprocessors continues to improve by leaps and bounds, fueled in part by rapid improvements in processor and interconnection technology. I/O performance thus becomes ever more critical, to avoid becoming the bottleneck of system performance. In this paper we provide an introduction to I/O architectural issues in multiprocessors, with a focus on disk subsystems. While we discuss examples from actual architectures and provide pointers to interesting research in the literature, we do not attempt to provide a comprehensive survey. We concentrate on a study of the architectural design issues, and the effects of different design alternatives.