r. ryne, nug mtg: 040625page 1 high energy physics greenbook presentation robert d. ryne lawrence...

R. Ryne, NUG mtg: 040625

High Energy Physics Greenbook Presentation

Robert D. RyneLawrence Berkeley National

Laboratory

NERSC User Group MeetingJune 25, 2005


Outline

Lattice QCD Accelerator Physics Astrophysics (see D. Olson’s presentation)


Lattice QCD


Goals

Determine a number of basic parameters of the Standard Model

Make precise tests of the Standard Model Obtain a quantitative understanding of the

physical phenomena controlled by the strong interactions


Impact on determination of CKM matrix

Improvements in lattice errors obtained w/ computers sustaining 0.6, 6, and 60 Tflops for one year


Computing Needs: Approach

Two pronged approach: Use of national supercomputer centers such as NERSC Build dedicated computers using special purpose

hardware for QCD- QCDOC

- Optimized clusters

Special purpose hardware is used to perform the majority of the lattice calculations

Supercomputer centers used for a combination of lattice calculations and data analysis


Computational Issues

Lattice calculations utilize a 4D grid Need highest possible single processor

performance Communication is nearest-neighbor Don’t need large memory Do need high speed networks

- International Lattice Data Grid formed to share computationally expensive data

- Need to move ~1 petabyte in 24 hrs


Lattice QCD Computational Roadmap

Lattice community presently sustains 0.5-1 Tflop/sec Has allowed determination of a limited number of key

quantities to ~few percent accuracy Has allowed development & testing of new formulations of

that will significantly improve accuracy of future calculations In next few years need to sustain 50-100 Tflop/sec

Calculate weak decay constants & form factors Determine phase diagram of high temp QCD, calculate EOS

of quark-gluon plasma Obtain quantitative understanding of internal structure of

strongly interacting particles Need to sustain ~ 1 petaflop/sec by end of decade


Accelerator Physics


Goals Large-scale modeling is essential for

Improving/upgrading existing accelerators Designing next-generation accelerators Exploring/discovering new methods of acceleration

- Laser/plasma based concepts


Accelerator modeling is very diverse

Many models Maxwell Vlasov/Poisson Vlasov/Maxwell Fokker-Planck Leonard-Weichart Single & multi-species

Particle based codes Mesh-based codes: regular, irregular, AMR,… Combined particle/mesh codes Runs of various sizes (up to ~1000 PEs and beyond)


Advanced Computing: An imperative to help assure success and best performance of a ~$20B investment

SciDAC budget is < 0.02% of the this amount Small investiment in computing can have huge

financial consequences


Accelerator Modeling Roadmap

Current resources: ~3M hrs/yr @ NERSC In the next few years, will need ~20M hrs/yr

Design of proposed machines: Linear Collider, RIA, hadron machines (proton drivers, muon/neutrino systems, VLHC)

Simulation of existing & near-term machines: LHC,RHIC, PEP-II, SNS Design of advanced concepts: 1 GeV stage, plasma afterburner Design of 4th generation light sources

By the end of the decade will need ~60M hrs/yr Full scale electron-cloud Multi-slice, multi-IP, strong-strong beam-beam Interaction of space charge effects, wakefields, and machine

nonlinearities in boosters and accumulator rings First principles Langevin modeling of electron cooling systems CSR effects with realistic boundary conditions

Goal is end-to-end modeling of complete systems


Algorithmic & Software Needs

Continued close collaboration with ASCR-supported researchers is essential Linear solvers, eigensolvers, PDE solvers, meshing

technologies, visualization Performance monitoring and enhancement, version

control & build tools, multi-language support Multi-scale methods are becoming increasingly

important We need robust, easy-to-use parallel programming

environments & parallel scientific software libraries


Parallel Optimization promises to be well suited for design problems on 10’s of thousands of processors

Machine design always involves multiple runs Up to now the community has learned how to run

large problems on ~thousand processors In the future, it will be desirable to run multiple

~1000 processor runs in a single optimization step Will allow scaling up to 10’s of thousands of processors

for machine design problems NOTE: not all problems are design problems. Fast

interprocessor communication is needed for the very largest “single point” runs.


Diversity of accelerator modeling problems demands a mix of capacity & capability, and a mix of system parameters

Some problems well suited to <=500 processors, but we typically need to run a large # of simulations Design studies, parameter scans

Some problems demand large simulations (>=1000) procs) and involve regular, near-neighbor comm. Electromagnetic PIC

Some problems demand large simulations and involve global, irregular communication Modeling geometrically complex electromagnetic structures


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r. ryne, nug mtg: 040625page 1 high energy physics greenbook presentation robert d. ryne lawrence...

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