Gary L. Hennigan

Simulation of neutron radiation damage in silicon semiconductor devices.

A code, Charon, is described which simulates the effects that neutron damage has on silicon semiconductor devices. The code uses a stabilized, finite-element discretization of the semiconductor drift-diffusion equations. The mathematical model used to simulate semiconductor devices in both normal and radiation environments will be described. Modeling of defect complexes is accomplished by adding an additional drift-diffusion equation for each of the defect species. Additionally, details are given describing how Charon can efficiently solve very large problems using modern parallel computers. Comparison between Charon and experiment will be given, as well as comparison with results from commercially-available TCAD codes.

High Performance MP Unstructured Finite Element Simulation of Chemically Reacting Flows

We describe the performance of MPSalsa, a MP code that simulates complex systems with strongly coupled fluid flow, thermal energy transfer, mass transfer and non-equilibrium chemical reactions. MPSalsa uses 3D unstructured finite element methods, fully implicit time integration, and general gas-phase and surface-species chemical kinetics to solve the coupled nonlinear PDEs on complex domains. It is designed around general kernels for domain partitioning, unstructured message passing, distributed sparse-block matrix representation of the fully summed global finite element equations, and preconditioned Krylov iterative solvers. Using these techniques, we obtained sustained rates of 210+ Gflop/s for a 3-D chemically reacting flow problem.

A 65+ Gflop/s unstructured finite element simulation of chemically reacting flows on the Intel Paragon

Many scientific and engineering applications require a detailed analysis of complex systems with strongly coupled fluid flow, thermal energy transfer mass transfer and nonequilibrium chemical reactions. Here we describe the performance of a newly developed application code, SALSA, designed to simulate these complex flows on large-scale parallel machines such as the Intel Paragon. SALSA uses 3D unstructured finite element methods to model geometrically complex flow systems. Fully implicit time integration, multicomponent mass transport and general gas phase and surface species non-equilibrium chemical kinetics are employed. Using these techniques we have obtained over 65 Gflop/s on a 3D chemically reacting flow CVD problem for Silicon Carbide (SiC) deposition. This represents 46% of the peak performance of our 1904 node Intel Paragon, an outstanding computational rate in view of the required unstructured data communication.<<ETX>>

Open-region, electromagnetic finite-element scattering calculations in anisotropic media on parallel computers

Open-region scattering calculations for complex, electrically large scatterers remains a difficult modeling and simulation problem. The finite-element method (FEM) has been shown to be a viable approach to solving such problems. However, conventional methods on serial computers limit the size which can be tackled with the FEM. In this paper, we demonstrate the use of both a PML boundary condition along with a parallel solver for tackling large, complex problems containing scatterers which are inhomogeneous and anisotropic.

Solution of Large, Sparse, Irregular Systems on a Massively Parallel Computer

A set of tools is introduced which allow engineers and scientists to obtain solutions to large finite-element problems by utilizing multiple-instruction, multiple-data (MIMD) parallel computers. The finite-element mesh is decomposed so that each resulting sub-domain is connected to at most two other subdomains. The node-numbering of the decomposed mesh is such that the resulting set of finite element equations will have a border-block diagonal structure. A parallel algorithm is used to assemble, factor and solve the set of simultaneous algebraic equations that result from the finite-element method (FEM). In this paper, we demonstrate the method on a message passing parallel computer for two- and three-dimensional electrostatic problems, governed by Laplaces equation. Results and performance data for the algorithm as applied to electrostatics problems are given. The current work is an extension of the algorithm described and implemented in Reference [1].

Using Domain Decomposition to Solve Positive-Definite Systems on the Hypercube Computer

A distributed method of solving sparse, positive-definite systems of equations on a hypercube computer, like those arising fiom many finite-element problems, is studied. A domain decomposition method is introduced wherein the domain of the problem to be solved is physically split into several sub-domains. This physical split is based on an ordering known as one-way dissection [ I ] . The one-way dissection ordering generates a block-diagonal system of equations which is well suited to a parallel implementation. Once the ordering has been accomplished each of the subdomains is then distributed to a processor in the hypercube computer as necessary. The method is applied to two-dimensional electrostatic problems which are governed by Laplace’s equation. Since the finite-element method is used to discretize the problem the method is developed to take full advantage of the inherent sparsity. The algorithm is applied to several geometries.