NERSCPowering Scientific Discovery Since 1974

Christopher Daley

Christopher Steven Daley
HPC Performance Engineer
Advanced Technology Group
Phone: (510) 486-4504
Fax: (510) 486-6459
National Energy Research Scientific Computing Center
1 Cyclotron Rd
Mailstop: 59R4010A (office 59-3027B)
Berkeley, California 94720 US

Biographical Sketch

Chris Daley is a member of the Advanced Technology Group (ATG).  Before joining ATG, Chris was a Scientific Programmer at the Flash Center for Computational Science at the University of Chicago.  He has a M.Sc. in High Performance Computing from the University of Edinburgh and a B.Sc. in Physics from the University of Surrey.

Journal Articles

C. S. Daley, D. Ghoshal, G. K. Lockwood, S. Dosanjh, L. Ramakrishnan, N. J. Wright, "Performance characterization of scientific workflows for the optimal use of Burst Buffers", Future Generation Computer Systems, December 28, 2017, doi: 10.1016/j.future.2017.12.022

Scientific discoveries are increasingly dependent upon the analysis of large volumes of data from observations and simulations of complex phenomena. Scientists compose the complex analyses as workflows and execute them on large-scale HPC systems. The workflow structures are in contrast with monolithic single simulations that have often been the primary use case on HPC systems. Simultaneously, new storage paradigms such as Burst Buffers are becoming available on HPC platforms. In this paper, we analyze the performance characteristics of a Burst Buffer and two representative scientific workflows with the aim of optimizing the usage of a Burst Buffer, extending our previous analyses (Daley et al., 2016). Our key contributions are a). developing a performance analysis methodology pertinent to Burst Buffers, b). improving the use of a Burst Buffer in workflows with bandwidth-sensitive and metadata-sensitive I/O workloads, c). highlighting the key data management challenges when incorporating a Burst Buffer in the studied scientific workflows.

J. Park, M. Smelyanskiy, K. Vaidyanathan, A. Heinecke, D Kalamkar, M Patwary, V. Pirogov, P. Dubey, X. Liu, C. Rosales, C. Mazauric, C. Daley, "Optimizations in a high-performance conjugate gradient benchmark for IA-based multi- and many-core processors", International Journal of High Performance Computing Applications, 2015, doi: 10.1177/1094342015593157

Jack Deslippe, Brian Austin, Chris Daley, Woo-Sun Yang, "Lessons learned from optimizing science kernels for Intel's "Knights-Corner" architecture", CISE, April 1, 2015,

A. Dubey, K. Antypas, A. C. Calder, C. Daley, B. Fryxell, J. B. Gallagher, D. Q. Lamb, D. Lee, K. Olson, L. B. Reid, P. Rich, P. M. Ricker, K. M. Riley, R. Rosner, A. Siegel, N. T. Taylor, K. Weide, F. X. Timmes, N. Vladimirova, and J. ZuHone, "Evolution of FLASH, a multi-physics scientific simulation code for high-performance computing", International Journal of High Performance Computing Applications, May 2014, doi: 10.1177/1094342013505656

A. Dubey, K. Weide, D. Lee, J. Bachan, C. Daley, S. Olofin, N. Taylor, P. M. Rich, and L. B. Reid, "Ongoing verification of a multiphysics community code: FLASH", Software: Practice and Experience, September 2013, doi: 10.1002/spe.2220

A. Dubey, A. Calder, C. Daley, C., R. Fisher, Jordan, D.Q. Lamb, L.B. Reid, D.M. Townsley, K. Weide, "Pragmatic Optimizations for Best Scientific Utilization of Large Supercomputers", International Journal of High Performance Computing Applications, July 2013, doi: 10.1177/1094342012464404

A. Dubey, C. Daley, J. ZuHone, P. M. Ricker, K. Weide, C. Graziani, "Imposing a Lagrangian Particle Framework on an Eulerian Hydrodynamics Infrastructure in FLASH", The Astrophysical Journal Supplements, 2012, 201:27, doi: 10.1088/0067-0049/201/2/27

C. Daley, M. Vanella, K. Weide, A. Dubey, E. Balaras, "Optimization of Multigrid Based Elliptic Solver for Large Scale Simulations the FLASH Code", Concurrency and Computation: Practice and Experience, 2012, 24:2346--2361, doi: 10.1002/cpe.2821

R. Latham, C. Daley, W.K. Liao, K. Gao, R. Ross, A. Dubey, A. Choudhary, "A case study for scientific I/O: improving the FLASH astrophysics code", Computational Science and Discovery, 2012, 5:015001, doi: 10.1088/1749-4699/5/1/015002

D. Lee, G. Xia, C. Daley, A. Dubey, S., C. Graziani, D.Q. Lamb, K. Weide, "Progress in development of HEDP capabilities in FLASH's Unsplit Staggered Mesh MHD solver", Astrophysics and Space Science, 2011, 336:157-162, doi: 10.1007/s10509-011-0654-5

B. R. de Supinski, S. Alam, D. H. Bailey, L., C. Daley, A. Dubey, T., D. Gunter, P. D. Hovland, H., K. Karavanic, G. Marin, J., S. Moore, B. Norris, L., C. Olschanowsky, P. C. Roth, M., S. Shende, A. Snavely, Spear, M. Tikir, J. Vetter, P. Worley, N. Wright, "Modeling the Office of Science ten year facilities plan: The PERI Architecture Tiger Team", Journal of Physics: Conference Series, 2009, 180:012039,

Conference Papers

B. Austin, C. Daley, D. Doerfler, J. Deslippe, B. Cook, B. Friesen, T. Kurth, C. Yang,
and N. Wright,
"A Metric for Evaluating Supercomputer Performance in the Era of Extreme Heterogeneity", 9th IEEE International Workshop on Performance Modeling, Benchmarking and Simulation of High Performance Computer Systems (PMBS'18), November 2018,

Tyler Allen, Christopher S. Daley, Douglas Doerfler, Brian Austin, Nicholas J. Wright, "Performance and Energy Usage of Workloads on KNL and Haswell Architectures", High Performance Computing Systems. Performance Modeling, Benchmarking, and Simulation. PMBS 2017. Lecture Notes in Computer Science, Volume 10724., December 23, 2017,

Wahid Bhimji, Debbie Bard, Kaylan Burleigh, Chris Daley, Steve Farrell, Markus Fasel, Brian Friesen, Lisa Gerhardt, Jialin Liu, Peter Nugent, Dave Paul, Jeff Porter, Vakho Tsulaia, "Extreme I/O on HPC for HEP using the Burst Buffer at NERSC", Journal of Physics: Conference Series, December 1, 2017, 898:082015,

C.S. Daley, D. Ghoshal, G.K. Lockwood, S. Dosanjh, L. Ramakrishnan, N.J. Wright, "Performance Characterization of Scientific Workflows for the Optimal Use of Burst Buffers", Workflows in Support of Large-Scale Science (WORKS-2016),, 2016, 1800:69-73,

W. Bhimji, D. Bard, M. Romanus, D. Paul, A. Ovsyannikov, B. Friesen, M. Bryson, J. Correa, G. K. Lockwood, V. Tsulaia, S. Byna, S. Farrell, D. Gursoy, C. Daley, V. Beckner, B. Van Straalen, D. Trebotich, C. Tull, G. Weber, N. J. Wright, K. Antypas, Prabhat, "Accelerating Science with the NERSC Burst Buffer Early User Program", Cray User Group, May 11, 2016, LBNL LBNL-1005736,

NVRAM-based Burst Buffers are an important part of the emerging HPC storage landscape. The National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory recently installed one of the first Burst Buffer systems as part of its new Cori supercomputer, collaborating with Cray on the development of the DataWarp software. NERSC has a diverse user base comprised of over 6500 users in 700 different projects spanning a wide variety of scientific computing applications. The use-cases of the Burst Buffer at NERSC are therefore also considerable and diverse. We describe here performance measurements and lessons learned from the Burst Buffer Early User Program at NERSC, which selected a number of research projects to gain early access to the Burst Buffer and exercise its capability to enable new scientific advancements. To the best of our knowledge this is the first time a Burst Buffer has been stressed at scale by diverse, real user workloads and therefore these lessons will be of considerable benefit to shaping the developing use of Burst Buffers at HPC centers.

C.S. Daley, L. Ramakrishnan, S. Dosanjh, N.J. Wright, "Analyses of Scientific Workflows for Effective Use of Future Architectures", The 6th International Workshop on Big Data Analytics: Challenges, and Opportunities (BDAC-15), 2015,

M. J. Cordery, B. Austin, H. J. Wasserman, C. S. Daley, N. J. Wright, S. D. Hammond, D. Doerfler, "Analysis of Cray XC30 Performance using Trinity-NERSC-8 benchmarks and comparison with Cray XE6 and IBM BG/Q", High Performance Computing Systems. Performance Modeling, Benchmarking and Simulation (PMBS 2013). Lecture Notes in Computer Science, Volume 8551, October 1, 2014,

P. Mohapatra, A Dubey, C. Daley, M. Vanella, and E. Balaras, "Parallel Algorithms for Using Lagrangian Markers in Immersed Boundary Method with Adaptive Mesh Refinement in FLASH", Computer Architecture and High Performance Computing (SBAC-PAD), October 2013, doi: 10.1109/SBAC-PAD.2013.27

C. Daley, J. Bachan, S. Couch, A. Dubey, M., B. Gallagher, D. Lee, K. Weide, "Adding shared memory parallelism to FLASH for many-core architectures", TACC-Intel Highly Parallel Computing Symposium, 2012,

V. Vishwanath, M. Hereld, M. E. Papka, R. Hudson, G. Jordan, C. Daley, "In Situ Data Analytics and I/O Acceleration of FLASH simulations on leadership-class systems with GLEAN", SciDAC, Journal of Physics: Conference Series, 2011,

A. Dubey, C. Daley, K. Weide, "Challenges of Computing with FLASH on Largest HPC Platforms", AIP Conference Proceedings, 2010, 1281:1773, doi:


C. Daley, Preparing for Mira: experience with FLASH multiphysics simulations, Mira Community Conference, 2013,


Glenn K. Lockwood, Damian Hazen, Quincey Koziol, Shane Canon, Katie Antypas, Jan Balewski, Nicholas Balthaser, Wahid Bhimji, James Botts, Jeff Broughton, Tina L. Butler, Gregory F. Butler, Ravi Cheema, Christopher Daley, Tina Declerck, Lisa Gerhardt, Wayne E. Hurlbert, Kristy A. Kallback-
Rose, Stephen Leak, Jason Lee, Rei Lee, Jialin Liu, Kirill Lozinskiy, David Paul, Prabhat, Cory Snavely, Jay Srinivasan, Tavia Stone Gibbins, Nicholas J. Wright,
"Storage 2020: A Vision for the Future of HPC Storage", October 20, 2017, LBNL LBNL-2001072,

As the DOE Office of Science's mission computing facility, NERSC will follow this roadmap and deploy these new storage technologies to continue delivering storage resources that meet the needs of its broad user community. NERSC's diversity of workflows encompass significant portions of open science workloads as well, and the findings presented in this report are also intended to be a blueprint for how the evolving storage landscape can be best utilized by the greater HPC community. Executing the strategy presented here will ensure that emerging I/O technologies will be both applicable to and effective in enabling scientific discovery through extreme-scale simulation and data analysis in the coming decade.