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Observations of an Accidental Computational Scientist SIAM/NSF/DOE CSME Workshop 25 March 2003 David Keyes Department of Mathematics & Statistics Old Dominion University & Institute for Scientific Computing Research Lawrence Livermore National Laboratory . Academic and lab backgrounds.

Academic and lab backgrounds

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Observations of an Accidental Computational ScientistSIAM/NSF/DOE CSME Workshop25 March 2003David KeyesDepartment of Mathematics & Statistics Old Dominion University&Institute for Scientific Computing ResearchLawrence Livermore National Laboratory

- 74-78: B.S.E., Aerospace and Mechanical/Engineering Physics
- 78-84: M.S. & Ph.D., Applied Mathematics
- 84-85: Post-doc, Computer Science
- 86-93: Asst./Assoc. Prof., Mechanical Engineering
- 93-99: Assoc. Prof., Computer Science
- 99-03: Prof., Mathematics & Statistics
- 03- : Prof., Applied Physics & Applied Mathematics

- 86-02: ICASE, NASA Langley

- 99- : ISCR, Lawrence Livermore
- 03- : CDIC, Brookhaven

- A “multidiscipline” on the verge of full bloom
- Envisioned by Von Neumann and others in the 1940’s
- Undergirded by theory (numerical analysis) for the past fifty years
- Empowered by spectacular advances in computer architecture over the last twenty years
- Enabled by powerful programming paradigms in the last decade

- Adopted in industrial and government applications
- Boeing 777’s computational design a renowned milestone
- DOE NNSA’s “ASCI” (motivated by CTBT)
- DOE SC’s “SciDAC” (motivated by Kyoto, etc.)

- Has theoretical aspects (modeling)
- Has experimental aspects (simulation)
- Unifies theory and experiment by providing common immersive environment for interacting with multiple data sets of different sources
- Provides “universal” tools, both hardware and software
Telescopes are for astronomers, microarray analyzers are for biologists, spectrometers are for chemists, and accelerators are for physicists, but computers are for everyone!

- Costs going down, capabilities going up every year

Engineering

electromagnetics

aerodynamics

Physicscosmology

radiation transport

Ex #2

Ex #3

Ex #1

Energycombustion fusion

Ex #4

personal examples

Experiments prohibited or impossible

Experiments difficult to instrument

Experiments dangerous

Experiments expensive

Environment

global climate

wildland firespread

Scientific Simulation

“It looks as if all of Colorado is burning” –

Bill Owens, Governor

“About half of the U.S. is in altered fire regimes” –

Ron Myers, Nature Conservancy

Simulate fires at the wildland-urban interface, leading to strategies for planning preventative burns, fire control, and evacuation

Joint work between ODU, CMU, Rice, Sandia, and TRW

- Objective
Develop mathematical models for tracking the evolution of wildland fires and the capability to fit the model to fires of different character (fuel density, moisture content, wind, topography, etc.)

- Accomplishment to date
Implemented firefront propagation with level set method with empirical front advance function; working with firespread experts to “tune” the resulting model

- Significance
Wildland fires cost many lives and billions of dollars annually; other fire models pursued at national labs are more detailed, but too slow to be used in real time; one of our objectives is to offer practical tools to firechiefs in the field

Simulate airflows over wings and streamlined bodies on highly resolved grids leading to superior aerodynamic design

1999 Gordon Bell Prize

Joint work between ODU, Argonne, LLNL, and NASA-Langley

- Objective
Develop analysis and optimization capability for compressible and incompressible external aerodynamics

- Accomplishment to date
Developed highly parallel nonlinear implicit solvers (Newton-Krylov-Schwarz) for unstructured grid CFD, implemented in PETSc, demonstrated on a “workhorse” NASA code running on the ASCI machines (up to 6,144 processors)

- Significance
Windtunnel tests of aerodynamic bodies are expensive and difficult to instrument; computational simulation and optimization (as for the Boeing 777) will greatly reduce the engineering risk of developing new fuel-efficient aircraft, cars, etc.

Simulate “flux-limited diffusion” transport of radiative energy in inhomogeneous materials

Joint work between ODU, ICASE, and LLNL

- Objective
Enhance accuracy and reliability of analysis methods used in the simulation of radiation transport in real materials

- Accomplishment to date
Leveraged expertise and software (PETSc) developed for aerodynamics simulations in a related physical application domain, also governed by nonlinear PDEs discretized on unstructured grids, where such methods were less developed

- Significance
Under current stockpile stewardship policies, DOE must be able to reliably predict the performance of high-energy devices without full-scale physical experiments

Simulate plasmas in tokomaks, leading to understanding of plasma instability and (ultimately) new energy sources

Joint work between ODU, Argonne, LLNL, and PPPL

- Objective
Improve efficiency and therefore extend predictive capabilities of Princeton’s leading magnetic fusion energy code “M3D” to enable it to operate in regimes where practical sustained controlled fusion occurs

- Accomplishment to date
Augmented the implicit linear solver (taking up to 90% of execution time) of original code with parallel algebraic multigrid; new solvers are much faster and robust, and should scale better to the finer mesh resolutions required for M3D

- Significance
An M3D-like code will be used in DOE’s Integrated Simulation and Optimization of Fusion Systems, and ITER collaborations, with the goal of delivering cheap safe fusion energy devices by early-to-mid 21st century

U.S. DOE has created the Terascale Optimal PDE Simulations (TOPS) project within the Scientific Discovery through Advanced Computing (SciDAC) initiative; nine partners in this 5-year, $17M project, an “Integrated Software Infrastructure Center”

Optimizer

Sens. Analyzer

Time integrator

Nonlinear solver

Eigensolver

Linear solver

Indicates dependence

- Design and implementation of “solvers”
- Time integrators
- Nonlinear solvers
- Constrained optimizers
- Linear solvers
- Eigensolvers

- Software integration
- Performance optimization

(w/ sens. anal.)

(w/ sens. anal.)

*Terascale Optimal PDE Simulations: www.tops-scidac.org

17 projects in scientific software and network infrastructure

SciDAC apps and infrastructure

4 projects in high energy and nuclearphysics

14 projects in biological and environmental research

10 projects in basic energy sciences

5 projects in fusion energy science

iters

200

unscalable

150

Time to Solution

100

50

procs

scalable

0

time

1000

1

10

100

Problem Size (increasing with number of processors)

- Convergence rate nearly independent of discretization parameters
- Multilevel schemes for linear and nonlinear problems
- Newton-like schemes for quadratic convergence of nonlinear problems

AMG shows perfect iteration scaling, above, in contrast to ASM, but still needs performance work to achieve temporal scaling, below, on CEMM fusion code, M3D, though time is halved (or better) for large runs (all runs: 4K dofs per processor)

Plan

Develop

Use

100+ Tflop / 30 TB

Livermore

50+ Tflop / 25 TB

30+ Tflop / 10 TB

Capability

10+ Tflop / 4 TB

White

3+ Tflop / 1.5 TB

Blue

Livermore

Red

1+ Tflop / 0.5 TB

‘97

‘98

‘99

‘00

‘01

‘02

‘03

‘04

‘05

‘06

Time (CY)

Sandia

Los Alamos

NNSA has roadmap to go to 100 Tflop/s by 2006

www.llnl.gov/asci/platforms

- IBM Power3+ SMP
- 16 procs per node
- 208 nodes
- 24 Gflop/s per node
- 5 Tflop/s (doubled in February to 10)

Berkeley

- IBM Power4 Regatta
- 32 procs per node
- 24 nodes
- 166 Gflop/s per node
- 4Tflop/s (10 in 2003)

Oak Ridge

- Launched in 1993 as “High Performance Computing”
- Keyes appointed ‘93; Pothen early ’94
- Major projects:
- NSF Grand, National, and Multidisciplinary Challenges (1995-1998) [w/ ANL, Boeing, Boulder, ND, NYU]
- DoEd Graduate Assistantships in Areas of National Need (1995-2001)
- DOE Accelerated Strategic Computing Initiative “Level 2” (1998-2001) [w/ ICASE]
- DOE Scientific Discovery through Advanced Computing (2001-2006) [w/ ANL, Berkeley, Boulder, CMU, LBNL, LLNL, NYU, Tennessee]
- NSF Information Technology Research (2001-2006) [w/ CMU, Rice, Sandia, TRW]

Center for Computational Science at ODU established 8/2001; new 80,000 sq ft building (for Math, CS, Aero, VMASC, CCS) opens 1/2004; finally getting local buy-in

ODU’s small program has placed five PhDs at DOE labs in the past three years

PETSc

CS&E

faculty

PETSc

PETSc

CCA

Comp

Bio

TOPS

Comp

Bio

David Hysom, LLNL

Florin Dobrian, ODU

Gary Kumfert, LLNL

Linda Stals, ANU

Dinesh Kaushik, ANL

Lois McInnes, ANL

Satish Balay, ANL

D. Karpeev, ANL

- Laboratory institutes (hosted at a lab)
ICASE, ISCR (more details to come)

- National institutes (hosted at a university)
IMA, IPAM

- Interdisciplinary centers
ASCI Alliances, SciDAC ISICs, SCCM, TICAM, CAAM, …

- CS&E fellowship programs
CSGF, HPCF

- Multi-agency funding (cyclical to be sure, but sometimes collaborative)
DOD, DOE, NASA, NIH, NSF, …

Serves as lab’s point of contact for computational science interests

Influences the external research community to pursue laboratory-related interests

Manages LLNL’s ASCI Institute collaborations in computer science and computational mathematics

Assists LLNL in technical workforce recruiting and training

- Be “eyes and ears” for LLNL by staying abreast of advances in computer and computational science
- Be “hands and feet” for LLNL by carrying those advances into the laboratory
- Three principal means for packaging scientific ideas for transfer
- papers
- software
- people

- People are the most effective!

Seminars & Visitors

180 visits from 147 visitors 66 ISCR seminars

ISCR

Summer Program43 grad students 29 undergrads 24 faculty

B451

Postdocs & Faculty 9 postdoctoral researchers3 faculty-in-residence

Workshops & Tutorials10 tutorial lectures6 technical workshops

- Founded in 1986
- Under current leadership since June 1999

ISCR has grown with LLNL’s increasing reliance on simulation as a predictive science

ASCI ASAP-1 Centers

Caltech

Stanford University

University of Chicago

University of Illinois

University of Utah

- Other Universities
Carnegie Mellon

Florida State University

MIT

Ohio State University

Old Dominion University

RPI

Texas A&M University

University of Colorado

University of Kentucky

University of Minnesota

University of N. Carolina

University of Tennessee

University of Texas

University of Washington

Virginia Tech

and more!

- University of California
Berkeley

Davis

Irvine

Los Angeles

San Diego

Santa Barbara

Santa Cruz

- Major European Centers
University of Bonn

University of Heidelberg

Students in residence hear from enthusiastic members of lab divisions, besides their own mentor, including five authors* of recent computational science books, on a variety of computational science topics

Lecturers: David Brown, Eric Cantu-Paz*, Alej Garcia*, Van Henson*, Chandrika Kamath, David Keyes, Alice Koniges*, Tanya Kostova, Gary Kumfert, John May*, Garry Rodrigue

Students

Faculty

Lab Employees

Faculty visit the ISCR, bringing students

Most faculty return to university, with lab priorities

Some students become lab employees

Some students become faculty, with lab priorities

A few faculty become lab employees

Universities

ISCR

Lab programs

- 178 ISCR summer students in past five years (many repeaters)
- 51 have by now emerged from the academic pipeline
- 23 of these (~45%) are now working for the DOE
- 15 LLNL
- 3 each LANL and Sandia
- 1 each ANL and BNL

- 11 of these (~20%) are in their first academic appointment
- In US: Duke, Stanford, U California, U Minnesota, U Montana, U North Carolina, U Pennsylvania, U Utah, U Washington
- Abroad: Swiss Federal Institute of Technology (ETH), University of Toronto

- Bay Area NA Day
- Common Component Architecture
- Copper Mountain Multigrid Conference
- DOE Computational Science Graduate Fellows
- Hybrid Particle-Mesh AMR Methods
- Mining Scientific Datasets
- Large-scale Nonlinear Problems
- Overset Grids & Solution Technology
- Programming ASCI White
- Sensitivity and Uncertainty Quantification

- Steve White, IBMASCI White overview, POWER3 architecture, tuning for White
- Larry Carter, UCSD/NPACIdesigning kernels and data structures for scientific applications, cache and TLB issues
- David Culler, UC Berkeleyunderstanding performance thresholds
- Clint Whalley, U Tennesseecoding for performance
- Bill Gropp, Argonne National LabMPI-1, Parallel I/O, MPI/OpenMP tradeoffs

65 internal attendees over 3 days

- Fred Brooks, UNC
- Ingrid Daubechies, Princeton
- David Johnson, AT&T
- Peter Lax, NYU
- Michael Norman, UCSD
- Charlie Peskin, NYU
- Gil Strang, MIT
- Burton Smith, Cray
- Eugene Spafford, Purdue
- Andries Van Dam, Brown

- A curricular challenge for CS&E programs
- Signs of the times for CS&E
- “Red skies at morning” ( “sailers take warning”)
- “Red skies at night” (“sailers delight”)

- Opportunities in which CS&E will shine
- A word to the sponsors

- CS&E majors without a CS undergrad need to learn to compute!
- Prerequisite or co-requisite to becoming useful interns at a lab
- Suggest a “bootcamp” year-long course introducing:
- C/C++ and object-oriented program design
- Data structures for scientific computing
- Message passing (e.g., MPI) and multithreaded (e.g., OpenMP) programming
- Scripting (e.g., Python)
- Linux clustering
- Scientific and performance visualization tools
- Profiling and debugging tools

- NYU’s sequence G22.1133/G22.1144 is an example for CS

- Difficult to get support for maintaining critical software infrastructure and “benchmarking” activities
- Difficult to get support for hardware that is designed with computational science and engineering in mind
- Difficult for pre-tenured faculty to find reward structures conducive to interdisciplinary efforts
- Unclear how stable is the market for CS&E graduates at the entrance to a 5-year pipeline
- Political necessity of creating new programs with each change of administrations saps time and energy of managers and community

- DOE’s SciDAC model being recognized and propagated
- NSF’s DMS budgets on a multi-year roll
- SIAM SIAG-CSE attracting members from outside of traditional SIAM departments
- CS&E programs beginning to exhibit “centripetal” potential in traditionally fragmented research universities
e.g., SCCM’s “Advice” program

- Computing at the large scale is weaning domain scientists from “Numerical Recipes” and MATLAB and creating thirst for core enabling technologies (NA, CS, Viz, …)
- Cost effectiveness of computing, especially cluster computing, is putting a premium on graduate students who have CS&E skills

- Jul 2002 report to DOE
- Proposes $5M/year theory and modeling initiative to accompany the existing $50M/year experimental initiative in nano science
- Report lays out research in numerical algorithms and optimization methods on the critical path to progress in nanotechnology

- Dec 2002 report to DOE
- Currently DOE supports 52 codes in Fusion Energy Sciences
- US contribution to ITER will “major” in simulation
- Initiative proposes to use advanced computer science techniques and numerical algorithms to improve the US code base in magnetic fusion energy and allow codes to interoperate

- Don’t cut off the current good stuff to start the new stuff
- Computational science & engineering workforce enters the pipeline from a variety of conventional inlets (disciplinary first, then interdisciplinary)
- Personal debts:
- NSF HSSRP in Chemistry (SDSU)
- NSF URP in Computer Science (Brandeis) – precursor to today’s REU
- NSF Graduate Fellowship in Applied Mathematics
- NSF individual PI grants in George Lea’s computational engineering program – really built community (Benninghof, Farhat, Ghattas, C. Mavriplis, Parsons, Powell + many others active in CS&E at labs, agencies, and universities today) at NSF-sponsored PI meetings, long before there was any university support at all

- Personal homepage: papers, talks, etc.
http://www.math.odu.edu/~keyes

- ISCR (including annual report) http://www.llnl.gov/casc/iscr
- SciDAC initiative
http://www.science.doe.gov/scidac

- TOPS software project
http://www.math.odu.edu/~keyes/scidac

64

64

2u=f

64

*On a 16 Mflop/s machine, six-months is reduced to 1 s

- Advances in algorithmic efficiency rival advances in hardware architecture
- Consider Poisson’s equation on a cube of size N=n3
- If n=64, this implies an overall reduction in flops of ~16 million

relative speedup

year

Algorithms and Moore’s Law

- This advance took place over a span of about 36 years, or 24 doubling times for Moore’s Law
- 22416 million the same as the factor from algorithms alone!

AMG Framework

error damped by pointwise relaxation

Choose coarse grids, transfer operators, etc. to eliminate, based on numerical weights, heuristics

- Since O(N) is already optimal, there is nowhere further “upward” to go in efficiency, but one must extend optimality “outward”, to more general problems
- Hence, for instance, algebraic multigrid (AMG), obtaining O(N) in anisotropic, inhomogeneous problems

algebraically smooth error