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Articles 1 - 15 of 15
Full-Text Articles in Physical Sciences and Mathematics
Building Segment Trees In Parallel, Peter Su, Scot Drysdale
Building Segment Trees In Parallel, Peter Su, Scot Drysdale
Computer Science Technical Reports
The segment tree is a simple and important data structure in computational geometry [7,11]. We present an experimental study of parallel algorithms for building segment trees. We analyze the algorithms in the context of both the PRAM (Parallel Random Access Machine) and hypercube architectures. In addition, we present performance data for implementations developed on the Connection Machine. We compare two different parallel alforitms, and we also compare our parallel algorithms to a good sequential algorithm for doing the same job. In this way, we evaluate the overall efficiency of our parallel methods. Our performance results illustrates the problems involved in …
Algorithms For Closest Point Problems: Practice And Theory, Peter Su
Algorithms For Closest Point Problems: Practice And Theory, Peter Su
Computer Science Technical Reports
This paper describes and evaluates know sequential algorithms for constructing planar Voronoi diagrams and Delaunay triangulations. In addition, it describes a new incremental algorithm which is simple to understand and implement, but whose performance is competitive with all known methods. The experiments in this paper are more than just simple benchmarks, they evaluate the expected performance of the algorithms in a precise and machine independent fashion. Thus, the paper also illustrates how to use experimental tools to both understand the behaviour of different algorithms and to guide the algorithm design process.
Formal Implementation Of High-Level Languages For Data-Parallel Programming, Deb Banerjee
Formal Implementation Of High-Level Languages For Data-Parallel Programming, Deb Banerjee
Dartmouth College Ph.D Dissertations
The success of parallel architectures has been limited by the lack of high-level parallel programming languages and useful programming models. The data-parallel model of programming has been demonstrated to be useful and natural on a wide variet of parallel architectures. This dissertation presents a set of formal techniques for compiling high- level languages based on data-parallelism.
Evidence For Helical Structures In Poly(1-Olefin Sulfones) By Transmission Electron Microscopy, George C. Ruben, W H. Stockmayer
Evidence For Helical Structures In Poly(1-Olefin Sulfones) By Transmission Electron Microscopy, George C. Ruben, W H. Stockmayer
Dartmouth Scholarship
Transmission electron microscope images were obtained of fractions of poly(1-tetradecene sulfone) and poly(cyclohexene sulfone) cast from very dilute solutions (0.007%, wt/vol) and rapidly freeze-dried on a mica surface. The samples were then vertically platinum-carbon (Pt-C) replicated with 9 +/- 0.3-A Pt-C and held together with 128 A of electron-transparent evaporated carbon. The Pt-C coating enlarges the molecular chain diameters by approximately 5 A, so that a single polysulfone chain has an apparent diameter of 9-12 A in the transmission electron microscope. Poly(1-tetradecene sulfone) forms short helical regions that show irregular helical turns of pitch 7-18 A, two to eight turns …
Multiprocessor File System Interfaces, David Kotz
Multiprocessor File System Interfaces, David Kotz
Dartmouth Scholarship
MIMD multiprocessors are increasingly used for production super-computing. Supercomputer applications often have tremendous file I/O requirements. Although newer I/O sub-systems, which attach multiple disks to the multiprocessor, permit parallel file access, file system software often has insufficient support for parallel access to the parallel disks, which is necessary for scalable performance. Most existing multiprocessor file systems are based on the conventional file system interface (which has operations like open, close, read, write, and seek). Although this provides the familiar file abstraction, it is difficult to use for parallel access to a file. Scalable applications must cooperate to read or write …
A Visualization System For Correctness Proofs Of Graph Algorithms, Peter A. Gloor, Donald B. Johnson, Fillia Makedon, Panagiotis Metaxas
A Visualization System For Correctness Proofs Of Graph Algorithms, Peter A. Gloor, Donald B. Johnson, Fillia Makedon, Panagiotis Metaxas
Computer Science Technical Reports
In this paper we describe a system for visualizing correctness proofs of graph algorithms. The system has been demonstrated for a greedy algorithm. Prim's algorithm for finding a minimum spanning tree of an undirected, weighted graph. We believe that our system is particularly appropriate for greedy algorithms, though much of what we discuss can guide visualization of proofs in other contexts. While an example is not a proof, our system provides concrete examples to illustrate the operation of the algorithm. These examples can be referred to by the user interactively and alternatively with the visualization of the proof where the …
Multiprocessor File System Interfaces, David Kotz
Multiprocessor File System Interfaces, David Kotz
Computer Science Technical Reports
Increasingly, file systems for multiprocessors are designed with parallel access to multiple disks, to keep I/O from becoming a serious bottleneck for parallel applications. Although file system software can transparently provide high-performance access to parallel disks, a new file system interface is needed to facilitate parallel access to a file from a parallel application. We describe the difficulties faced when using the conventional (Unix-like) interface in parallel applications, and then outline ways to extend the conventional interface to provide convenient access to the file for parallel programs, while retaining the traditional interface for programs that have no need for explicitly …
Multiprocessor File System Interfaces, David Kotz
Multiprocessor File System Interfaces, David Kotz
Dartmouth Scholarship
Increasingly, file systems for multiprocessors are designed with parallel access to multiple disks, to keep I/O from becoming a serious bottleneck for parallel applications. Although file system software can transparently provide high-performance access to parallel disks, a new file system interface is needed to facilitate parallel access to a file from a parallel application. We describe the difficulties faced when using the conventional (Unix-like) interface in parallel applications, and then outline ways to extend the conventional interface to provide convenient access to the file for parallel programs, while retaining the traditional interface for programs that have no need for explicitly …
Environmental Education, Daniel Lynch, Charles Hutchinson
Environmental Education, Daniel Lynch, Charles Hutchinson
Dartmouth Scholarship
The need for a new profession devoted to environmental matters is asserted. The qualities of such a profession are sketched, and it is argued that new initiatives in environmental education are needed in the form of graduate, professional programs with primary emphasis on practice. An example 2-year program is presented. A fundamental requirement is scientific competence; undergraduate preparation in the sciences or engineering is mandatory. The graduate curriculum itself is built on three primary cores: environmental science and engineering, business and management, and public policy. Additionally, an environmental round table is proposed as a focal point for academic, industrial, governmental, …
The 14.8-H Orbital Period Of Gx339-4, P. J. Callanan, P. A. Charles, W. B. Honey, J. R. Thorstensen
The 14.8-H Orbital Period Of Gx339-4, P. J. Callanan, P. A. Charles, W. B. Honey, J. R. Thorstensen
Dartmouth Scholarship
We present the results of photometric observations of the black hole candidate GX339-4, obtained while the system was in an 'off' state. We show that a 14.8-h modulation was present, and provide evidence for a similar periodicity in the 'high' state from a reanalysis of previously published photometry and spectroscopy. The presence of the same period in both states implies that it is likely to be the orbital period of the system. The spectroscopy analysis provides evidence for an apparent change in the systemic velocity of the system. The amplitude of the observed radial velocity variations, however, permits only crude …
Spede: A Simple Programming Environment For Distributed Execution (Users' Manual), James Gochee
Spede: A Simple Programming Environment For Distributed Execution (Users' Manual), James Gochee
Dartmouth College Undergraduate Theses
Traditional single processor computers are quickly reaching their full computational potentials. The quest for faster and faster chips have brought technology to the point where the laws of physics are hampering future gains. Significant gains in speed must therefore come from using multiple processors instead of a single processor. This technology usually represents itself in the form of a parallel computer, such as the Connection Machine Model 5. Recently however, much interest has been focused on software that organizes single processor computers to behave like a parallel computer. This is desirable for sites which have large installations of workstations, since …
Spede: Simple Programming Environment For Distributed Execution, James Gochee
Spede: Simple Programming Environment For Distributed Execution, James Gochee
Dartmouth College Undergraduate Theses
One of the main goals for people who use computer systems, particularly computational scientists, is speed. In the quest for ways to make applications run faster, engineers have developed parallel computers, which use more than one CPU to solve a task. However, many institutions already posses significant computational power in networks of workstations. Through software, it is possible to glue together clusters of machines to simulate a parallel environment. SPEDE is one such system, designed to place the potential of local machines at the fingertips of the programmer. Through a simple interface, users design computational objects that can be linked …
How To Encrypt /Usr/Dict/Words In About A Second, Peter Su, Matt Bishop
How To Encrypt /Usr/Dict/Words In About A Second, Peter Su, Matt Bishop
Computer Science Technical Reports
We present an implementation of the Data Encryption Standard on the Connection Machine architecture. The DES encryption algorithm is ideally suited to the Connection Machine because it consists of bit serial operations, and thousands of encryptions can be done in parallel, independently of one another. Thus, our code encrypts passwords about ten times faster than the fastest competition that we know about. In addition, the nature of the Connection Machine's architecture is such that some of the optimizations that make DES run much faster on conventional architectures have no effect on the performance of the Connection Machine. Our comparison of …
On The De Bruijn Torus Problem, Glenn Hurlbert, Garth Isaak
On The De Bruijn Torus Problem, Glenn Hurlbert, Garth Isaak
Computer Science Technical Reports
A (kn;n)k-de Bruijn Cycle is a cyclic k-ary sequence with the property that every k-ary n-tuple appears exactly once contiguously on the cycle. A (kr, ks; m, n)k-de Bruijn Torus is a k-ary krXks toroidal array with the property that every k-ary m x n matrix appears exactly once contiguously on the torus. As is the case with de Bruijn cycles, the 2-dimensional version has many interesting applications, from coding and communications to pseudo-random arrays, spectral imaging, and robot self-location. J.C. Cock proved the existence of such tori for all m, n, and k, and Chung, Diaconis, and Graham asked …
Concurrent Local Search For Fast Proximity Algorithms On Parallel And Vector Architectures, Peter Su
Concurrent Local Search For Fast Proximity Algorithms On Parallel And Vector Architectures, Peter Su
Computer Science Technical Reports
This paper presents a fast algorithm for solving the all-nearest-neighbors problem. The algorithm uses a data parallel style of programming which can be efficiently utilized on a variety of parallel and vector architectures [4,21,26]. I have implemented the algorithm in C on one such architecture, the Cray Y-MP. On one Cray CPU, the implementation is about 19 times faster than a fast sequential algorithm running on a Sparc workstation. The main idea in the algorithm is to divide the plane up into a fixed grid of cells, or buckets. When the points are well distributed, the algorithm processes each query …