Engineering topics

Fahey, Mark R

Publications and source records attributed to Fahey, Mark R.

5 records

DOE OSTI2014

Performance of the fusion code GYRO on four generations of Cray computers

GYRO is a code used for the direct numerical simulation of plasma microturbulence. It has been ported to a variety of modern MPP platforms including several modern commodity clusters, IBM SPs, and Cray XC, XT, and XE series machines. We briefly describe the mathematical structure of the equations, the data layout, and the redistribution scheme. Also, while the performance and scaling of GYRO on many of these systems has been shown before, here we show the comparative performance and scaling on four generations of Cray supercomputers including the newest addition - the Cray XC30. The more recently added hybrid OpenMP/MPI imple- mentation also shows a great deal of promise on custom HPC systems that utilize fast CPUs and proprietary interconnects. Four machines of varying sizes were used in the experiment, all of which are located at the National Institute for Computational Sciences at the University of Tennessee at Knoxville and Oak Ridge National Laboratory. The advantages, limitations, and performance of using each system are discussed.

Fahey, Mark R↗

DOE OSTI2014

Deploying Darter A Cray XC30 System

TheUniversityofTennessee,KnoxvilleacquiredaCrayXC30 supercomputer, called Darter, with a peak performance of 248.9 Ter- aflops. Darter was deployed in late March of 2013 with a very aggressive production timeline - the system was deployed, accepted, and placed into production in only 2 weeks. The Spring Experiment for the Center for Analysis and Prediction of Storms (CAPS) largely drove the accelerated timeline, as the experiment was scheduled to start in mid-April. The Consortium for Advanced Simulation of Light Water Reactors (CASL) project also needed access and was able to meet their tight deadlines on the newly acquired XC30. Darter s accelerated deployment and op- erations schedule resulted in substantial scientific impacts within the re- search community as well as immediate real-world impacts such as early severe tornado warnings

Fahey, Mark R↗

DOE OSTI2014

A leap forward with UTK s Cray XC30

This paper shows a significant productivity leap for several science groups and the accomplishments they have made to date on Darter - a Cray XC30 at the University of Tennessee Knoxville. The increased productivity is due to faster processors and interconnect combined in a new generation from Cray, and yet it still has a very similar programming environment as compared to previous generations of Cray machines that makes porting easy.

Fahey, Mark R↗

DOE OSTI2014

Reproducibility responsibilities in the HPC arena

Expecting bit-for-bit reproducibility in the HPC arena is not feasible because of the ever changing hardware and software. No user s application is an island; it lives in an HPC eco-system that changes over time. Old hardware stops working and even old software won t run on new hardware. Further, software libraries change over time either by changing the internals or even interfaces. So bit-for-bit reproducibility should not be expected. Rather a reasonable expectation is that results are reproducible within error bounds; or that the answers are close (which is its own debate.) To expect a researcher to reproduce their own results or the results of others within some error bounds, there must be enough information to recreate all the details of the experiment. This requires complete documentation of all phases of the researcher s workflow; from code to versioning to programming and runtime environments to publishing of data. This argument is the core statement of the Yale 2009 Declaration on Reproducible Research [1]. Although the HPC ecosystem is often outside the researchers control, the application code could be built almost identically and there is a chance for very similar results with just only round-off error differences. To achieve complete documentation at every step, the researcher, the computing center, and the funding agencies all have a role. In this thesis, the role of the researcher is expanded upon as compared to the Yale report and the role of the computing centers is described.

Fahey, Mark R↗

DOE OSTI2014

User Environment Tracking and Problem Detection with XALT

This work improves our understanding of individual users software needs, then leverages that understanding to help stakeholders conduct business in a more efficient, effective, and systematic way. The product, XALT, builds on work that is already improving the user experience and enhancing support programs for thousands of users on twelve supercomputers across the United States and Europe. XALT will instrument individual jobs on high-end computers to generate a picture of the compilers, libraries, and other software that users need to run their jobs successfully. It will highlight the products our researchers need and do not need, and alert users and support staff to the root causes of software configuration issues as soon as the problems occur. A key objective of this work is generating the information needed to improve efficiency and effectiveness for an extensive community of stakeholders including users, sponsoring institutions, support organizations, and development teams. Efficiency, effectiveness, and responsible stewardship each require a clear picture of users needs. XALT is an important step in the quest to achieve that clarity.

Agrawal, Kapil↗