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An Accelerated Strategic Computing Initiative (ASCI) Academic Strategic Alliances Program (ASAP) Center
at The University of Chicago
The Center for Astrophysical Thermonuclear Flashes
An Overview of the ASCI/Alliances Program at Chicago:
Year 3 Site Review
Robert Rosner, DirectorOctober 30, 2000
Chicago, IL(http://flash.uchicago.edu)
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
What is the FLASH Problem?
To simulate matter accumulation on the surface of compact stars, nuclear ignition of the accreted (and possibly underlying stellar) material, and the subsequent evolution of the star’s interior, surface, and exterior• X-ray bursts (on neutron star surfaces)• Novae (on white dwarf surfaces)• Type Ia supernovae (in white dwarf interiors)
Credit: NASA/STScI
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Observations of Astrophysical Flashes
Credit: NASA/Rossi XTE
Credit: NASA/STScICredit: NASA/STScI
Type Ia SN: SN 1994D
Nova: Nova Cygni 1992
X-ray burst: GS 1826-24
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Schematics of the astrophysical problems
Type Ia supernova
X-ray burst (neutron star)Nova (white dwarf)
White dwarf
White dwarf/neutron star
White dwarf: R ~ REarth
(C, O) Neutron star: R ~ RChicago
(Neutrons)
H, He
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Why are these interesting problems - Part 1
Defense programsParadigm for attacking physics problem without ability to
experimentTraining of the next generation of computational
scientistsFLASH is the only Center which includes MHD
AstrophysicsEndpoints of accretionNucleosynthesis of elementsCosmology
Physics Interface instabilities, mixingFundamentals of combustion
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Why are these interesting problems - Part 2
Computational Science Integration of complex physicsExploration of grids, hydro algorithms, ...Practical application of OO-based programming
paradigm Sociology
Mixing astrophysicists, physicists, applied mathematicians, computer scientists …
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
What are the FLASH Center’s Goals?
To build a new-generation simulation code for computing astrophysical thermonuclear flashes involving compact stars Incorporate advances from CS, applied math,
physics modular, reusable code
Verify and validate code and its components
To produce great scienceAstrophysics and physicsComputational sciences [CS, Applied math, Math]
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
The Challenges
Extreme dynamic ranges of spatial and temporal phenomena AMR, subgrid modeling, front tracking
Large dynamic range of flow velocities Accurate computation of very low and high Mach number flows
Physical processes can be highly localized and non-uniform Load balancing
Physical processes can be non-local Example: Elliptic solvers on AMR grid
Rapidly evolving computing environment Creation of programming and computing environment
Astrophysical validation is extremely indirect Development of laboratory proxy validation experiments
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
What have we accomplished to date?
We are on track: we have a newly architected code Production version: Flash-1.61 OO-based data structures introduced: Flash-2 (in test) We have started on all three astrophysics problems
We responded to past Site Review suggestions Management changes Code architecture
We have obtained exciting science results
(Y. Young 2000)
(M. ZIngale 2000)
(N. Vladimirova 2000)
(F. Timmes 2000) (A. Calder 2000)
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
What you’ll hear about today
Talks
Flash Code: B. Fryxell, P. Ricker, A. Siegel
Astrophysics: J. Truran
Basic Science/Validation: T. Dupont
Computer Science: E. Lusk
Posters
Astro, CS, Math, Physics
Demos
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
What’s New in Year 3: Part 1
Re-organization Code group and Computational Physics combined Code architecture team formed within Code group: Code architect! Management team tightened
T. Dupont (Basic Sci/Validation), B. Fryxell (Code), E. Lusk (CS), R. Rosner (director), R. Stevens (ex officio), J. Truran (Astro)
Weekly management team meeting
Focus on re-engineering Flash Re-engineered OO-based architecture: Flash-1.6 Current optimized production version: Flash-1.61
Includes improved version of Paramesh New features incorporated in Flash-2.0 (now in active test)
OO-based data structures and data-sharing: Paves the way for extensibility of Flash
Python-based user interface, setup, automatic test facility, tools, …
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
What’s New in Year 3: Part 2
Focus on basic science Cellular detonations Interface mixing: R-T/R-M, wave breaking Flame propagation/modeling MHD Rad. transfer Implicit conduction Self-consistent gravity
Focus on astrophysics X-ray bursts Novae Type Ia supernovae
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
How was this done: Our strategy
Initial instantiation of Flash Code: Flash 1.0 Legacy hydro solver (“Prometheus”/F77) New adaptive mesh package (“Paramesh”/F90) New physics packages (nuclear reaction networks, EOS/F90)
“Classic” modular designAllowed first-cut astrophysics and validation calculationsGuided refinement of code architecture
New architecture code OO-based code architecture/framework
Optimized for productionNew module interface designAllows continued use as applications codeGradual transition to/introduction of object-oriented programming
Physics modules Automatic code verification/test facility New data sharing scheme Revised user interface
“Crude, but useful” Dick Watson (1999)
Flash-2.0
Flash-1.61
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
How was this done: Our Center’s structure
AstrophysicsJ. Truran
ComputerScience
R. Lusk
Basic Science& Validation
T. Dupont
FLASH CodeB. Fryxell
Chan, Clark,Curfman-McInnes,
Foster, Freitag,Flaherty, Gomez,Gropp, Hudson,
Loy, PapkaScott, Shephard,
Smith, Stevens, Tufo
Calder, Linde,Mignone,
Olson, Ricker,Timmes, Tufo, Weirs, Zingale
Arnett, Brown,Calder,Dursi, Fryxell, Lamb,
Mignone, Peng,Ricker, Timmes, Zingale
Caceres, Ricker,Reilly,
Vladimirova,K. Young
Alexakis, Constantin,Curtis, Draganescu,Kadanoff, Litwin, Liu,Medved, Oberman,
Ruchayski, Vladimirova, Y. Young
LANL, LLNL, MPIUCSC,
SUNY, UA, NWUCollaborators
Model problems(R-T, …)
Code Architecture,grids/AMR
Sub-grid turbulence,combustion,front tracking
LANL, LLNL,SNL, PPPL
PSU,LANL, LLNL,
SNL
Cattaneo, Constantin, Dupont, Dursi, Fryxell, Malagoli,Oberman, Rosner, Vladimirova, Weirs, Young
Curfman-McInnes, Flaherty, Freitag, Fryxell, Malagoli,Olson, Ricker, Scott, Shephard, Siegel, Tufo
Alexakis, Calder, Cattaneo, Constantin, Dupont, Flaherty, Fryxell, Kadanoff, Litwin, Niemeyer,Oberman, Olson, Rosner, Scott, Shephard, Tufo, Young
Clark, Chan, Freitag, Fryxell, Gomez, Gropp, Lusk, Olson,Siegel, Smith, Timmes, Tufo, Zingale
Performance/tuning,scaling
Astrophysics modules,Astrophysics
simulations andvalidation
Tool kits, Libraries,Visualization
Validation experiments,Fundamental physics
PhysicsModules
Architectureteam
A. Siegel
LANL, LLNL,SNL
GSFC
WorkingGroups
Ad hoc groups
Development,Maintenance,
& Testing
Calder, Dursi,Olson, Ricker,Timmes, Tufo,
Zingale
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
How was this done: Effective interactions
Flash CodeGroup
Astrophysics Group
Basic Science/Validation Group
Computer Science Group
Production CodeAstrophys. modules
Production Code
Validation, models
Code
Vis., Tools, Architect.
Monday 2:00pm Astro meeting
Monday 3:00pm Code/CS meeting
Wednesday 12:30pm Comp. Sci seminar
Wednesday 10:00am FlamesWednesday 11:00am MHD
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Responses to Year 2 Site Review: Part 1
Concerns regarding progress on Flash code Decision regarding Flash architecture
Re-architected Flash exists! See talks by B. Fryxell/P. Ricker/A. Siegel “Insertion plan”
Plan for module insertion in place and being exercised; see talk by A. Siegel
Concerns regarding physics modules Nuclear reactions
See talk by J. Truran Radiative transport
See poster by A. Calder
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Responses to Year 2 Site Review: Part 2
Concerns regarding Center management and staffing Management structure tightened Code architect
A. Siegel (Flash-2 on) P. Ricker (Basic Flash architecture)
Code group leader B. Fryxell
Executive director Center consensus: position not needed
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
Training the next generation ...
Name Field Present position
Graduates:Y. Liu fluid dynamics (Math) postdoc/SUNY Stony Brook, winter 1999-00R. Loy algorithms (CS) staff member/ANL, fall 1999M. Zingale astro/theory (A&A) postdoc /A&A, fall 2000Y.N. Young fluid dynamics (A&A) postdoc at Northwestern/Applied Math, fall 2000S. Wunsch fluid dynamics (Physics) postdoc, A. Kerstein/Sandia/Livermore, fall 1998S. Zhan astro/theory (A&A) financial company, spring 2000
Current:A. Alexaksis MHD student/physicsJ. Biello fluid dynamics (A&A) postdoc at RPI/Applied Math, fall 2000A. Caceres comp. physics student/physicsJ. Curtis fluid dynamics student/physicsA. Draganescu algorithms student/mathematicsJ. Dursi astro/theory student/A&A Sandia/summer 2000E. Gomez parallel tools (CS) assoc. professor at UC San Bernardino, fall
2000A. Mignone MHD student/A&AA. Oberman combustion student/mathematics Sandia/summer 2000M. Papka visualization student/CS & staff member/ANLF. Peng comp. Astro student/A&AO. Ruchayskiy fluid dynamics student/physics
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
The Future of Flash: The larger picture
1. Follow the FLASH Center plan Continue Flash code development: push extensibility Pursue Flash development for the 3 astrophysics problems Pursue Astrophysics, Basic Science/Validation, and
Computer Science activities as planned
2. Up the ante …go beyond our earlier ambitions Include new physics features not previously planned on
Two-fluid hydro/MHD N-body
Attack FLASH-related astrophysics problems not in original FLASH Center plan
Accretion flows and disks Stellar evolution (including star formation)
Explore new ideas from CS and computational science Exploratory/collaborative computing
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
A final comment and summary
Project oversight by DOE has been productive First-rate scientists appointed as project managers Project oriented toward helping Centers succeed
Annual external site review Annual DOE-only site visit Constant interactions on science
We have succeeded in getting where we wanted to be, and in some cases, are further along than anticipated New architecture in place, and producing many science results All astrophysics problems have been started, with astro. results Center structure has evolved to function effectively
The challenges Effective validation and model building is very hard … Available computational resources no longer match our needs
The ASCI/Alliances Center for Astrophysical Thermonuclear FlashesThe University of Chicago
… and that leads us to
QUESTIONS AND DISCUSSION