National Energy Research Scientific Computing Center 2007 Annual Report

This report presents highlights of the research conducted on NERSC computers in a variety of scientific disciplines during the year 2007. It also reports on changes and upgrades to NERSC's systems and services aswell as activities of NERSC staff

Organizational Learning From Information System-Related Incidents

Aquesta tesi analitza com les organitzacions intenten palanquejar l’experiència dels ISRI (information system-related incidents) per tal d’evitar la recurrència de fallades i reduir-ne els impactes. En conseqüència, per estudiar-ho s’adopta una perspectiva d’aprenentatge situat i una visió pràctica per tal de respondre la pregunta: “Com aprenen les organitzacions de SI dels seus principals incidents interns, relacionats amb els sistemes d’informació?” Mitjançant el disseny d’un cas múltiple i inductiu, aquest estudi arriba a la conclusió que les organitzacions adopten una gran varietat de pràctiques durant i després del procés de gestió d’un incident. Això ha portat a l’articulació de cinc formes d’aprenentatge: 1) l’aprenentatge mitjançant la gestió de l’incident, 2) la reflexió posterior a l’incident, 3) l’aprenentatge transversal, 4) l’aprenentatge externalitzat i 5) l’aprenentatge a través de la substitució material. Si bé les dues primeres formes d’aprenentatge estan documentades en altres camps, aquest estudi mostra que les característiques dels ISRI afecten les pràctiques relacionades amb aquestes dues formes d’aprenentatge. A més, l’anàlisi se centra també en les altres tres formes, que semblen típiques d’aquest sector. L’aprenentatge transversal fa referència al fet que mentre algunes pràctiques d’aprenentatge se centren en incidents individuals, hi ha unes pràctiques específiques d’aprenentatge que tenen en compte molts esdeveniments adversos. L’aprenentatge externalitzat indica que l’experiència que s’obté d’un incident sovint es capitalitza confiant en proveïdors especialitzats a gestionar incidents. Finalment, la naturalesa particular dels processos de treball de la SI i la seva base material permeten aprendre a través de la substitució material. Aquesta tesi enriqueix la nostra comprensió dels processos pels quals les organitzacions aprenen dels ISRI i, per tant, contribueix als desenvolupaments teòrics de la literatura sobre el coneixement i l’aprenentatge. Més concretament, els resultats d’aquesta recerca qüestionen la visió temporal establerta sobre quan es produeix un procés d’aprenentatge. Si bé la literatura existent en matèria d’aprenentatge organitzacional assenyala que l’aprenentatge té lloc durant l’incident (a través de pràctiques de gestió de l’incident) o (immediatament) després (a través de la reflexió i l’aprenentatge posteriors a l’incident), aquest estudi suggereix que el model temporal del procés d’aprenentatge no s’exhaureix necessàriament en aquesta dicotomia. El concepte d’aprenentatge transversal indica la importància d’observar les pràctiques d’aprenentatge que tenen lloc paral•lelament i a una distància temporal considerable dels incidents que es produeixen en un moment adequat d’aprenentatge. La tesi se suma a la literatura sobre el coneixement destacant la importància dels règims de materialitat subjacents en el procés d’aprenentatge. La idea de l’aprenentatge a través de la substitució material mostra que el règim modular i adaptable de la materialitat que domina en els ISRI pot portar les organitzacions a beneficiar-se de la seva experiència en incidents, sense conèixer-ne necessàriament les causes i les seves possibles solucions. Finalment, la tesi ens ajuda a comprendre millor el rol de la política i la governança de l’aprenentatge a partir dels incidents en el sector de la SI. I ho fa en subratllar els rols de neutralització (enfront de normalització) i de dramatització (enfront de racionalització) en el procés d’aprenentatge. Aquest estudi ha descobert que la ignorància dels actors influents en els aspectes tècnics del problema pot aprofitar-se per part dels agents d’aprenentatge per tal de sumar-se a la pressió política necessària per impulsar les iniciatives d’aprenentatge. L’estudi també destaca la importància crítica de la governança organitzacional per al procés d’aprenentatge. El concepte d’aprenentatge externalitzat subratlla la importància del sistema de governança de l’aprenentatge, que complementa les dues governances d’aprenentatge dominants en la literatura –és a dir, l’aprenentatge intraorganitzatiu i l’interorganitzatiu. Això demostra que, per treure profit de les experiències d’incidents passats, les organitzacions poden evitar fer pràctiques d’aprenentatge, especialment quan tracten amb una gran varietat de tecnologies canviants (abstinència d’aprenentatge), perquè el coneixement que se n’obtingui probablement serà obsolet o perdrà valor amb el temps.Esta tesis analiza cómo las organizaciones intentan apalancar la experiencia de los ISRI (information system-related incidents) para evitar la recurrencia de fallos y reducir sus impactos. En consecuencia, para su estudio se adopta una perspectiva de aprendizaje situado y una visión práctica para dar respuesta a la pregunta: “¿Cómo aprenden las organizaciones de SI de sus principales incidentes internos, relacionados con los sistemas de información?” Mediante un diseño de un caso múltiple e inductivo, este estudio llega a la conclusión que las organizaciones adoptan una gran variedad de prácticas durante y después del proceso de gestión de un incidente. Esto ha llevado a la articulación de cinco modos de aprendizaje: 1) aprendizaje mediante la gestión del incidente, 2) reflexión posterior al incidente, 3) aprendizaje transversal, 4) aprendizaje externalizado y 5) aprendizaje a través de la sustitución material. Si bien los dos primeros modos de aprendizaje están documentados en otros campos, el presente estudio muestra que las características de los ISRI afectan las prácticas relacionadas con estos dos modos de aprendizaje. Además, el análisis se centra también en los otros tres modos, que parecen típicos de este sector. El aprendizaje transversal se refiere al hecho de que mientras algunas prácticas de aprendizaje se centran en incidentes individuales, existen prácticas específicas de aprendizaje que tienen en cuenta múltiples eventos adversos. El aprendizaje externalizado indica que la experiencia que se obtiene de un incidente con frecuencia se capitaliza confiando en proveedores especializados en gestionar incidentes. Finalmente, la naturaleza particular de los procesos de trabajo de la SI y su base material permiten aprender a través de la sustitución material. Esta tesis enriquece nuestra comprensión de los procesos por los cuales las organizaciones aprenden de los ISRI y, por tanto, contribuye a los desarrollos teóricos de la literatura sobre el conocimiento y el aprendizaje. Más específicamente, los resultados de esta investigación cuestionan la visión temporal establecida sobre cuándo se produce un proceso de aprendizaje. Si bien la literatura existente en materia de aprendizaje organizacional señala que el aprendizaje tiene lugar durante el incidente (a través de prácticas de gestión del incidente) o (inmediatamente) después (a través de la reflexión y el aprendizaje posteriores al incidente), el presente estudio sugiere que el modelo temporal del proceso de aprendizaje no se restringe necesariamente a esta dicotomía. El concepto de aprendizaje transversal indica la importancia de observar las prácticas de aprendizaje que tienen lugar paralelamente y a una distancia temporal considerable de los incidentes que se producen en un momento adecuado de aprendizaje. La tesis se suma a la literatura sobre el conocimiento destacando la importancia de los regímenes de materialidad subyacentes en el proceso de aprendizaje. La idea del aprendizaje a través de la sustitución material muestra que el régimen modular y adaptable de la materialidad que domina en los ISRI puede llevar a las organizaciones a beneficiarse de su experiencia en incidentes, sin conocer necesariamente las causas de dichos incidentes y sus posibles soluciones. Finalmente, la tesis mejora nuestra comprensión del rol de la política y la gobernanza del aprendizaje a partir de los incidentes en el sector de la SI. Al efecto, subraya los roles de neutralización (frente a normalización) y dramatización (frente a racionalización) en el proceso de aprendizaje. Este estudio ha descubierto que la ignorancia de los actores influyentes en los aspectos técnicos del problema puede ser aprovechado por los agentes de aprendizaje para sumarse a la presión política necesaria para impulsar las iniciativas de aprendizaje. El estudio también destaca la importancia crítica de la gobernanza organizacional para el proceso de aprendizaje. El concepto de aprendizaje externalizado subraya la importancia del sistema de gobernanza del aprendizaje, que complementa las dos gobernanzas de aprendizaje dominantes en la literatura –es decir, el aprendizaje intraorganizativo y el interorganizativo. Ello demuestra que, para sacar provecho de las experiencias de incidentes pasados, las organizaciones pueden evitar realizar prácticas de aprendizaje, especialmente cuando tratan con una gran variedad de tecnologías cambiantes (abstinencia de aprendizaje), puesto que el conocimiento que se obtiene probablemente será obsoleto o perderá valor con el tiempo.This thesis examines how organizations try to leverage the experience of major information system-related incident (ISRI) to avoid the recurrence of failure and to reduce their impacts. Accordingly, the study utilizes a situated learning perspective and a practice view to respond to the question “how do IS organizations learn from their internal, large Information system-related incidents?” Employing a multiple, inductive case study design, the study found that organizations adopt a wide range of practices during and after the incident handling process. This resulted in articulating five learning modes: 1) learning through incident handling, 2) post-incident reflection, 3) transversal learning, 4) outsourced learning, and 5) learning through material replacement. Although the first two learning modes are documented in other domains, the study shows how the characteristics of ISRIs affect the practices associated to these two learning modes. Further, the analysis focuses on the other three learning modes that seem to be typical of this sector. Transversal learning refers to the fact that while some of the learning practices are focused on individual incidents, specific learning practices exist which take into account multiple adverse events. Outsourced learning indicates that capitalizing on the experience of an incident is often carried out through relying on specialized providers that handle incidents. Finally, the particular nature of the IS work processes and its material basis allow for learning through material replacement. The thesis enriches our understanding of the processes whereby organizations learn from ISRIs, thus providing contributions to theoretical developments in knowledge and learning literature. More specifically, the results of the research challenge the established temporal view about when learning process takes place. While the existing literature on organizational learning suggests that learning takes place either during incident (through incident handling practices) or (right) after (through post-incident reflection and learning), the current study suggests that the temporal pattern of learning process is not necessarily confined to this established dichotomy. The concept of transversal learning indicates the importance of looking at learning practices that take place in parallel and with a considerable temporal distance from incidents that occur in a proper moment of learning. The thesis adds to knowledge literature by foregrounding the importance of the materiality regimes underlying the learning process. The idea of learning through material replacement shows that the modular, adaptable regime of materiality that dominates ISRIs can lead organizations to benefit from their incident experience, without necessarily knowing the causes of incidents and their potential solutions. Finally, the thesis advances our understanding of the role of politics and governance of learning from incidents in the IS sector. It does so by highlighting the role of neutralization (versus normalization) and dramatization (versus rationalization) in the process of learning. The study found that the ignorance of influential actors about the technical aspects of the problem could be leveraged by learning agents to add to the political pressure needed to drive learning initiatives. The study also highlights the critical importance of organizational governance for the process of learning. The concept of outsourced learning underscores the importance of a learning governance system, which complements the two dominant learning governances in the literature –i.e., intra and inter-organizational learning. This shows that for capitalizing on the experiences of past incidents, organizations might avoid performing learning practices, especially when they are dealing with a wide range of changing technologies (learning abstinence), since the knowledge gained is expected to be obsolete or decrease in value through time

A scalable packetised radio astronomy imager

Includes bibliographical referencesModern radio astronomy telescopes the world over require digital back-ends. The complexity of these systems depends on many site-specific factors, including the number of antennas, beams and frequency channels and the bandwidth to be processed. With the increasing popularity for ever larger interferometric arrays, the processing requirements for these back-ends have increased significantly. While the techniques for building these back-ends are well understood, every installation typically still takes many years to develop as the instruments use highly specialised, custom hardware in order to cope with the demanding engineering requirements. Modern technology has enabled reprogrammable FPGA-based processing boards, together with packet-based switching techniques, to perform all the digital signal processing requirements of a modern radio telescope array. The various instruments used by radio telescopes are functionally very different, but the component operations remain remarkably similar and many share core functionalities. Generic processing platforms are thus able to share signal processing libraries and can acquire different personalities to perform different functions simply by reprogramming them and rerouting the data appropriately. Furthermore, Ethernet-based packet-switched networks are highly flexible and scalable, enabling the same instrument design to be scaled to larger installations simply by adding additional processing nodes and larger network switches. The ability of a packetised network to transfer data to arbitrary processing nodes, along with these nodes' reconfigurability, allows for unrestrained partitioning of designs and resource allocation. This thesis describes the design and construction of the first working radio astronomy imaging instrument hosted on Ethernet-interconnected re- programmable FPGA hardware. I attempt to establish an optimal packetised architecture for the most popular instruments with particular attention to the core array functions of correlation and beamforming. Emphasis is placed on requirements for South Africa's MeerKAT array. A demonstration system is constructed and deployed on the KAT-7 array, MeerKAT's prototype. This research promises reduced instrument development time, lower costs, improved reliability and closer collaboration between telescope design teams

Software for Exascale Computing - SPPEXA 2016-2019

This open access book summarizes the research done and results obtained in the second funding phase of the Priority Program 1648 "Software for Exascale Computing" (SPPEXA) of the German Research Foundation (DFG) presented at the SPPEXA Symposium in Dresden during October 21-23, 2019. In that respect, it both represents a continuation of Vol. 113 in Springer’s series Lecture Notes in Computational Science and Engineering, the corresponding report of SPPEXA’s first funding phase, and provides an overview of SPPEXA’s contributions towards exascale computing in today's sumpercomputer technology. The individual chapters address one or more of the research directions (1) computational algorithms, (2) system software, (3) application software, (4) data management and exploration, (5) programming, and (6) software tools. The book has an interdisciplinary appeal: scholars from computational sub-fields in computer science, mathematics, physics, or engineering will find it of particular interest

An FPGA implementation of an investigative many-core processor, Fynbos : in support of a Fortran autoparallelising software pipeline

Includes bibliographical references.In light of the power, memory, ILP, and utilisation walls facing the computing industry, this work examines the hypothetical many-core approach to finding greater compute performance and efficiency. In order to achieve greater efficiency in an environment in which Moore’s law continues but TDP has been capped, a means of deriving performance from dark and dim silicon is needed. The many-core hypothesis is one approach to exploiting these available transistors efficiently. As understood in this work, it involves trading in hardware control complexity for hundreds to thousands of parallel simple processing elements, and operating at a clock speed sufficiently low as to allow the efficiency gains of near threshold voltage operation. Performance is there- fore dependant on exploiting a new degree of fine-grained parallelism such as is currently only found in GPGPUs, but in a manner that is not as restrictive in application domain range. While removing the complex control hardware of traditional CPUs provides space for more arithmetic hardware, a basic level of control is still required. For a number of reasons this work chooses to replace this control largely with static scheduling. This pushes the burden of control primarily to the software and specifically the compiler, rather not to the programmer or to an application specific means of control simplification. An existing legacy tool chain capable of autoparallelising sequential Fortran code to the degree of parallelism necessary for many-core exists. This work implements a many-core architecture to match it. Prototyping the design on an FPGA, it is possible to examine the real world performance of the compiler-architecture system to a greater degree than simulation only would allow. Comparing theoretical peak performance and real performance in a case study application, the system is found to be more efficient than any other reviewed, but to also significantly under perform relative to current competing architectures. This failing is apportioned to taking the need for simple hardware too far, and an inability to implement static scheduling mitigating tactics due to lack of support for such in the compiler

Bibliography of Lewis Research Center Technical Publications announced in 1991

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific engineering work performed and managed by the Lewis Research Center in 1991. All the publications were announced in the 1991 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Simplified vector-thread architectures for flexible and efficient data-parallel accelerators

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 165-170).This thesis explores a new approach to building data-parallel accelerators that is based on simplifying the instruction set, microarchitecture, and programming methodology for a vector-thread architecture. The thesis begins by categorizing regular and irregular data-level parallelism (DLP), before presenting several architectural design patterns for data-parallel accelerators including the multiple-instruction multiple-data (MIMD) pattern, the vector single-instruction multiple-data (vector-SIMD) pattern, the single-instruction multiple-thread (SIMT) pattern, and the vector-thread (VT) pattern. Our recently proposed VT pattern includes many control threads that each manage their own array of microthreads. The control thread uses vector memory instructions to efficiently move data and vector fetch instructions to broadcast scalar instructions to all microthreads. These vector mechanisms are complemented by the ability for each microthread to direct its own control flow. In this thesis, I introduce various techniques for building simplified instances of the VT pattern. I propose unifying the VT control-thread and microthread scalar instruction sets to simplify the microarchitecture and programming methodology. I propose a new single-lane VT microarchitecture based on minimal changes to the vector-SIMD pattern.(cont.) Single-lane cores are simpler to implement than multi-lane cores and can achieve similar energy efficiency. This new microarchitecture uses control processor embedding to mitigate the area overhead of single-lane cores, and uses vector fragments to more efficiently handle both regular and irregular DLP as compared to previous VT architectures. I also propose an explicitly data-parallel VT programming methodology that is based on a slightly modified scalar compiler. This methodology is easier to use than assembly programming, yet simpler to implement than an automatically vectorizing compiler. To evaluate these ideas, we have begun implementing the Maven data-parallel accelerator. This thesis compares a simplified Maven VT core to MIMD, vector-SIMD, and SIMT cores. We have implemented these cores with an ASIC methodology, and I use the resulting gate-level models to evaluate the area, performance, and energy of several compiled microbenchmarks. This work is the first detailed quantitative comparison of the VT pattern to other patterns. My results suggest that future data-parallel accelerators based on simplified VT architectures should be able to combine the energy efficiency of vector-SIMD accelerators with the flexibility of MIMD accelerators.by Christopher Francis Batten.Ph.D

Applied Metaheuristic Computing

For decades, Applied Metaheuristic Computing (AMC) has been a prevailing optimization technique for tackling perplexing engineering and business problems, such as scheduling, routing, ordering, bin packing, assignment, facility layout planning, among others. This is partly because the classic exact methods are constrained with prior assumptions, and partly due to the heuristics being problem-dependent and lacking generalization. AMC, on the contrary, guides the course of low-level heuristics to search beyond the local optimality, which impairs the capability of traditional computation methods. This topic series has collected quality papers proposing cutting-edge methodology and innovative applications which drive the advances of AMC