A design methodology for portable software on parallel computers

This final report for research that was supported by grant number NAG-1-995 documents our progress in addressing two difficulties in parallel programming. The first difficulty is developing software that will execute quickly on a parallel computer. The second difficulty is transporting software between dissimilar parallel computers. In general, we expect that more hardware-specific information will be included in software designs for parallel computers than in designs for sequential computers. This inclusion is an instance of portability being sacrificed for high performance. New parallel computers are being introduced frequently. Trying to keep one's software on the current high performance hardware, a software developer almost continually faces yet another expensive software transportation. The problem of the proposed research is to create a design methodology that helps designers to more precisely control both portability and hardware-specific programming details. The proposed research emphasizes programming for scientific applications. We completed our study of the parallelizability of a subsystem of the NASA Earth Radiation Budget Experiment (ERBE) data processing system. This work is summarized in section two. A more detailed description is provided in Appendix A ('Programming Practices to Support Eventual Parallelism'). Mr. Chrisman, a graduate student, wrote and successfully defended a Ph.D. dissertation proposal which describes our research associated with the issues of software portability and high performance. The list of research tasks are specified in the proposal. The proposal 'A Design Methodology for Portable Software on Parallel Computers' is summarized in section three and is provided in its entirety in Appendix B. We are currently studying a proposed subsystem of the NASA Clouds and the Earth's Radiant Energy System (CERES) data processing system. This software is the proof-of-concept for the Ph.D. dissertation. We have implemented and measured the performance of a portion of this subsystem on the Intel iPSC/2 parallel computer. These results are provided in section four. Our future work is summarized in section five, our acknowledgements are stated in section six, and references for published papers associated with NAG-1-995 are provided in section seven

Limits to parallelism in scientific computing

The goal of our research is to decrease the execution time of scientific computing applications. We exploit the application\u27s inherent parallelism to achieve this goal. This exploitation is expensive as we analyze sequential applications and port them to parallel computers. Many scientifically computational problems appear to have considerable exploitable parallelism; however, upon implementing a parallel solution on a parallel computer, limits to the parallelism are encountered. Unfortunately, many of these limits are characteristic of a specific parallel computer. This thesis explores these limits.;We study the feasibility of exploiting the inherent parallelism of four NASA scientific computing applications. We use simple models to predict each application\u27s degree of parallelism at several levels of granularity. From this analysis, we conclude that it is infeasible to exploit the inherent parallelism of two of the four applications. The interprocessor communication of one application is too expensive relative to its computation cost. The input and output costs of the other application are too expensive relative to its computation cost. We exploit the parallelism of the remaining two applications and measure their performance on an Intel iPSC/2 parallel computer. We parallelize an Optimal Control Boundary Value Problem. This guidance control problem determines an optimal trajectory of a boat in a river. We parallelize the Carbon Dioxide Slicing technique which is a macrophysical cloud property retrieval algorithm. This technique computes the height at the top of a cloud using cloud imager measurements. We consider the feasibility of exploiting its massive parallelism on a MasPar MP-2 parallel computer. We conclude that many limits to parallelism are surmountable while other limits are inescapable.;From these limits, we elucidate some fundamental issues that must be considered when porting similar problems to yet-to-be designed computers. We conclude that the technological improvements to reduce the isolation of computational units frees a programmer from many of the programmer\u27s current concerns about the granularity of the work. We also conclude that the technological improvements to relax the regimented guidance of the computational units allows a programmer to exploit the inherent heterogeneous parallelism of many applications

Procesamiento paralelo : Conceptos de arquitecturas y algoritmos

Históricamente, la única forma de tratar algunos problemas de procesamiento ha sido por medio de cómputo paralelo. A mayor complejidad de cálculo y mayor compromiso con la ejecución en tiempo real (inteligencia artificial, redes neuronales, rebotica, reconocimiento de patrones, visualización científica, modelos de elementos finitos y de fluidos, manejo de grandes bases de datos, etc.), se hace imprescindible utilizar procesamiento paralelo para obtener tiempos de respuesta aceptables. En los primeros capítulos de este libro se analizan aspectos de la arquitectura (organización del control, memoria y comunicaciones) de los sistemas de procesamiento paralelo. En los capítulos intermedios se tratan algorítmicamente clases de problemas de cómputo paralelo como los de cálculo numérico, ordenación, grafos e imágenes. Se discuten los temas de concurrencia y sincronización entre procesos que se ejecutan en paralelo. Asimismo se analizan parámetros de rendimiento tales como el factor de Speed-Up y el grado de paralelismo alcanzable en los ejemplos que se exponen. En los últimos capítulos se desarrolla extensivamente el problema de migración de procesos en arquitecturas paralelas distribuidas. Se presenta un entorno de experimentación (diseño e implementación) de migración de procesos, así como resultados de experimentación con distintas políticas de manejo de mensajes. La intención de este libro no es abarcar todos los temas posibles de lo que tradicionalmente se ha denominado procesamiento paralelo. Lo que sí se intenta conservar son las ideas de aplicación y rendimiento del procesamiento paralelo, estudiando casos y problemas con el enfoque de optimizar el diseño de la arquitectura y del software. La idea subyacente de aplicación del cómputo paralelo guía en cierto sentido la presentación de los temas. Se hacen explícitas las simplificaciones y suposiciones en los análisis teóricos presentados y se discuten los ejemplos tratando de extraer de ellos las ideas comunes con respecto a la clase de problemas a la que pertenecen.Tesis digitalizada en SEDICI gracias a la Biblioteca del Departamento de Matemática de la Facultad de Ciencias Exactas (UNLP).Facultad de Ciencias Exacta