18699103
Experiences of Parallelising Finite-element Problems in a Functional Style
Experiences are described of parallelizing a functional finite-element program (written in Haskell) for the solution of computational fluid-dynamics problems. A transformation prototyping approach using a system developed at the University of York, which simulates idealised parallel machines on a conventional sequential workstation, is presented. In this paper we demonstrate: (a) the relative simplicity of the functional approach for parallelizing a complex program compared with the conventional procedural approach; (b) the suitability of functional languages for prototyping parallel algorithms to improve an implementation; and (c) the considerable assistance provided by the simulator.
35595997
Parallel simulation of a multi-dimensional computational fluid dynamics problem
The simulation of computational fluid dynamics problems in two and more dimensions involves computations of multiple degrees of freedom, such as the components of velocity, which are an obvious source of parallelism. Further to our previous investigation in this area we report on our current experiences in extracting such parallelism on a distributed network platform. A finite element method for simulating incompressible viscous flows is parallelised using a domain decomposition approach. Various issues that arise in this implementation are discussed in the light of our experimental results.
27831253
Sparse Matrix Representations in a Functional Language
This paper investigates several sparse matrix representation schemes and associated algorithms in Haskell for solving linear systems of equations arising from solving realistic computational fluid dynamics problems using a finite element algorithm. This work complements that of Wainwright and Sexton (1992) in that a Choleski direct solver (with an emphasis on its forward/backward substitution steps) is examined. Experimental evidence comparing time and space efficiency of these matrix representation schemes is reported, together with associated forward/backward substitution implementations. Our results are in general agreement with Wainwright and Sexton's.
21113650
A Discrete-Time Queuing Analysis of the Wireless ATM Multiplexing System
In this paper we analyze a wireless channel model which is subject to service interruption either because the channel is not available or the server is serving to the other users. The wireless channel is modeled by a Markov chain with two states corresponding to high and low error states, respectively. It is assumed that the channel is slotted in time and no transmission is possible during the high-error state. The traffic generated by a mobile user is modeled as the superposition of independent two states On-Off Markov sources, which are statistically independent of the server. A source generates packets only during an On state each of which fits to a channel slot. A discrete-time queuing analysis derives the probability generating function (PGF) of the queue length under the assumption of an infinite buffer. From the PGF, mean queue length, mean delay and approximate finite buffer overflow probabilities are calculated.
16742949
Evaluation of the matrix exponential function using finite elements in time
The evaluation of a matrix exponential function is a classic problem of computational linear algebra. Many different methods have been employed for its numerical evaluation (Moler C and van Loan C 1978 SIAM Review 20 4), none of which produce a definitive algorithm which is broadly applicable and sufficiently accurate, as well as being reasonably fast. Herein, we employ a method which evaulates a matrix exponential as the solution to a first-order initial value problem in a fictitious time variable. The new aspect of the present implementation of this method is to use finite elements in the fictitious time variable. (Weatherford C A, Red E, and Wynn A 2002 Journal of Molecular Structure 592 47) Then using an expansion in a properly chosen time basis, we are able to make accurate calculations of the exponential of any given matrix as the solution to a set of simultaneous equations.
32875582
Invariant object recognition by shape space analysis
This paper describes a new approach to invariant object recognition. In this approach, an object is represented by a set of key points called landmarks. All possible translation, scaling, and rotation of the object are placed into an equivalent class and associated to a single point in a complex projective space called the shape space. Object recognition is then achieved by distance calculations in this shape space. This approach is invariant to object translation, scaling, and rotation, and is computationally simple. Our experimental results also indicate that it is insensitive to noise and moderate occlusions.
37723019
Mining Influential Association Rules
15371796
ACTIVE: agile coordinator testbed integrated virtual environment
This paper describes the specification, design and development of ACTIVE, a testbed for the testing and simulation of large-scale agent-based systems. ACTIVE is being developed as part of DARPA's Coordinators program. The goal of the ACTIVE testbed is to support the simulation of large collections of distributed cooperating agents in solving constrained scheduling problems.