2,257 research outputs found
Automating embedded analysis capabilities and managing software complexity in multiphysics simulation part I: template-based generic programming
An approach for incorporating embedded simulation and analysis capabilities
in complex simulation codes through template-based generic programming is
presented. This approach relies on templating and operator overloading within
the C++ language to transform a given calculation into one that can compute a
variety of additional quantities that are necessary for many state-of-the-art
simulation and analysis algorithms. An approach for incorporating these ideas
into complex simulation codes through general graph-based assembly is also
presented. These ideas have been implemented within a set of packages in the
Trilinos framework and are demonstrated on a simple problem from chemical
engineering
SPAR data handling utilities
The SPAR computer software system is a collection of processors that perform particular steps in the finite-element structural analysis procedure. The data generated by each processor are stored on a data base complex residing on an auxiliary storage device, and these data are then used by subsequent processors. The SPAR data handling utilities use routines to transfer data between the processors and the data base complex. A detailed description of the data base complex organization is presented. A discussion of how these SPAR data handling utilities are used in an application program to perform desired user functions is given with the steps necessary to convert an existing program to a SPAR processor by incorporating these utilities. Finally, a sample SPAR processor is included to illustrate the use of the data handling utilities
A NASA family of minicomputer systems, Appendix A
This investigation was undertaken to establish sufficient specifications, or standards, for minicomputer hardware and software to provide NASA with realizable economics in quantity purchases, interchangeability of minicomputers, software, storage and peripherals, and a uniformly high quality. The standards will define minicomputer system component types, each specialized to its intended NASA application, in as many levels of capacity as required
LATENT VARIABLE GENERALIZED LINEAR MODELS
Generalized Linear Models (GLMs) (McCullagh and Nelder, 1989) provide a
unified framework for fixed effect models where response data arise from exponential family
distributions. Much recent research has attempted to extend the framework to include
random effects in the linear predictors. Different methodologies have been employed to
solve different motivating problems, for example Generalized Linear Mixed Models
(Clayton, 1994) and Multilevel Models (Goldstein, 1995). A thorough review and
classification of this and related material is presented. In Item Response Theory (IRT)
subjects are tested using banks of pre-calibrated test items. A useful model is based on the
logistic function with a binary response dependent on the unknown ability of the subject.
Item parameters contribute to the probability of a correct response. Within the framework
of the GLM, a latent variable, the unknown ability, is introduced as a new component of the
linear predictor. This approach affords the opportunity to structure intercept and slope
parameters so that item characteristics are represented. A methodology for fitting such
GLMs with latent variables, based on the EM algorithm (Dempster, Laird and Rubin, 1977)
and using standard Generalized Linear Model fitting software GLIM (Payne, 1987) to
perform the expectation step, is developed and applied to a model for binary response data.
Accurate numerical integration to evaluate the likelihood functions is a vital part of the
computational process. A study of the comparative benefits of two different integration
strategies is undertaken and leads to the adoption, unusually, of Gauss-Legendre rules. It is
shown how the fitting algorithms are implemented with GLIM programs which incorporate
FORTRAN subroutines. Examples from IRT are given. A simulation study is undertaken to
investigate the sampling distributions of the estimators and the effect of certain numerical
attributes of the computational process. Finally a generalized latent variable model is
developed for responses from any exponential family distribution
New Techniques for On-line Testing and Fault Mitigation in GPUs
L'abstract è presente nell'allegato / the abstract is in the attachmen
RVSDG: An Intermediate Representation for Optimizing Compilers
Intermediate Representations (IRs) are central to optimizing compilers as the
way the program is represented may enhance or limit analyses and
transformations. Suitable IRs focus on exposing the most relevant information
and establish invariants that different compiler passes can rely on. While
control-flow centric IRs appear to be a natural fit for imperative programming
languages, analyses required by compilers have increasingly shifted to
understand data dependencies and work at multiple abstraction layers at the
same time. This is partially evidenced in recent developments such as the MLIR
proposed by Google. However, rigorous use of data flow centric IRs in general
purpose compilers has not been evaluated for feasibility and usability as
previous works provide no practical implementations. We present the
Regionalized Value State Dependence Graph (RVSDG) IR for optimizing compilers.
The RVSDG is a data flow centric IR where nodes represent computations, edges
represent computational dependencies, and regions capture the hierarchical
structure of programs. It represents programs in demand-dependence form,
implicitly supports structured control flow, and models entire programs within
a single IR. We provide a complete specification of the RVSDG, construction and
destruction methods, as well as exemplify its utility by presenting Dead Node
and Common Node Elimination optimizations. We implemented a prototype compiler
and evaluate it in terms of performance, code size, compilation time, and
representational overhead. Our results indicate that the RVSDG can serve as a
competitive IR in optimizing compilers while reducing complexity
Modular digital holographic fringe data processing system
A software architecture suitable for reducing holographic fringe data into useful engineering data is developed and tested. The results, along with a detailed description of the proposed architecture for a Modular Digital Fringe Analysis System, are presented
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