| 1. |
- Markidis, Stefano, et al.
(författare)
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Paving the path to exascale computing with CRESTA development environment
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The development and implementation of efficient computer codes for exascale supercomputers will require combined advancement of all development environment components: compilers, automatic tuning frameworks, run-time systems, debuggers and performance monitoring and analysis tools. The exascale era poses unprecedented challenges. Because the presence of accelerators is more and more common among the fastest supercomputer and will play a role in exascale computing, compilers will need to support hybrid computer architectures and generate efficient code hiding the complexity of programming accelerators. Hand optimization of the code will be very difficult on exascale machine and will be increasingly assisted by automatic tuners. Application tuning will be more focus on parallel aspects of the computation because of large amount of available parallelism. The application workload will be distributed over million of processes, and to implement ad-hoc strategies directly in the application will be probably unfeasible while an adaptive run-time system will provide automatic load balancing. Debuggers and performance monitoring tools will deal with million processes and with huge amount of data from application and hardware counters, but they will still be required to minimize the overhead and retain scalability. In this talk, we present how the development environment of the CRESTA exascale EC project meets all these challenges by advancing the state of the art in the field.An investigation of compiler support for hybrid GPU programming, the design concepts, and the main characteristics of the alpha prototype implementation of the CRESTA development environment components for exascale computing are presented. A performance study of OpenACC compiler directives has been carried out, showing very promising results and indicating OpenACC as viable approach for programming hybrid exascale supercomputer. A new Domain-Specific Language (DSL) has been defined for the expression of parallel auto-tuning at very large scale. The focus of on the extension of the auto-tuning approach into the parallel domain to enable tuning of communication-related aspects of application. A new adaptive run-time system has been designed to schedule processes depending on the resource availability, on the workload, and on the run-time analysis of the application performance. The Allinea DDT debugger and the Dresden University of Technology MUST MPI correctness checker are being extended to provide a unified interface, to improve scalability, and to include new disruptive technology based on statistical analysis of run-time behavior of the application for anomalies detection. The new exascale prototypes of the Dresden University of Technology Vampir, VampirTrace and Score-P performance monitoring and analysis tools have been released. The new features include the possibility of applying filtering technique before loading performance data to drastically reduce memory needs during the performance analysis. The initial evaluation study of the development environment is targeted on the CRESTA project applications to determine how the development environment could be coupled into a production suite for exascale computing.
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| 2. |
- Aguilar, Xavier
(författare)
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Towards Scalable Performance Analysis of MPI Parallel Applications
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A considerably fraction of science discovery is nowadays relying on computer simulations. High Performance Computing (HPC) provides scientists with the means to simulate processes ranging from climate modeling to protein folding. However, achieving good application performance and making an optimal use of HPC resources is a heroic task due to the complexity of parallel software. Therefore, performance tools and runtime systems that help users to execute applications in the most optimal way are of utmost importance in the landscape of HPC. In this thesis, we explore different techniques to tackle the challenges of collecting, storing, and using fine-grained performance data. First, we investigate the automatic use of real-time performance data in order to run applications in an optimal way. To that end, we present a prototype of an adaptive task-based runtime system that uses real-time performance data for task scheduling. This runtime system has a performance monitoring component that provides real-time access to the performance behavior of anapplication while it runs. The implementation of this monitoring component is presented and evaluated within this thesis. Secondly, we explore lossless compression approaches for MPI monitoring. One of the main problems that performance tools face is the huge amount of fine-grained data that can be generated from an instrumented application. Collecting fine-grained data from a program is the best method to uncover the root causes of performance bottlenecks, however, it is unfeasible with extremely parallel applications or applications with long execution times. On the other hand, collecting coarse-grained data is scalable but sometimes not enough to discern the root cause of a performance problem. Thus, we propose a new method for performance monitoring of MPI programs using event flow graphs. Event flow graphs provide very low overhead in terms of execution time and storage size, and can be used to reconstruct fine-grained trace files of application events ordered in time.
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| 3. |
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| 4. |
- Brunet, Manola, et al.
(författare)
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Long-term changes in extreme temperatures and precipitation in Spain
- 2007
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Ingår i: Contributions to Science: The International Journal of the Institute for Catalan Studies (IEC). - 1575-6343. ; 3:3, s. 331-342
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The development of the Spanish daily adjusted temperatureseries (SDATS) and the Spanish daily adjusted precipitation series(SDAPS) datasets in the framework of the European Community(EC)-funded project EMULATE (European and North Atlanticdaily to MULtidecadal climATE variability) enabled theassessment of long-term annual changes of extreme temperatureand precipitation indices over peninsular Spain for the period1901–2005. Within this framework, a set of procedureswas developed to generate long-term (1850–2005) daily adjustedtemperature and precipitation series and to use them toassess changes in climatic extremes. The present report describesdetails of the data employed to analyze the behavior ofSpanish climate extremes and discusses the results of investigationsinto the annual changes in selected indices that occurredduring the 20th century: exceedances of upper and lowerpercentiles of daily maximum (Tmax) and minimum (Tmin)temperatures, cold-spell duration index (CSDI), warm-spell durationindex (WSDI), daily rainfall (R) exceeding the 95th and 99thpercentiles, simple daily intensity index (SDII), and greatest 1–and 5-day total precipitation. Upper and lower temperaturepercentiles increased during the 20th century over mainlandSpain, but changes in daytime extreme temperatures werelarger than the changes in night-time extreme temperatures.This pattern, however, shifted slightly in the recent period ofstrong warming, with more similar rates of change among daytimeand night-time extreme temperatures. Changes in extremeprecipitation indices were not as evident as those in extreme-temperature indices, but there was a tendency towardsheavier precipitation.
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