QCD Project Overview

Ying Zhang

September 26, 2005

DOE SciDAC Program

Scientific Discovery through advanced Computing Funded by Department of Energy, the Office of Science (SC) http://www.scidac.org/

Goals: Translate the computing technology advances in 21st century

into corresponding increases in the capabilities of scientific codes

Research, development and deployment of software to accelerate the development of scientific codes and to achieve maximum efficiency on high-end computers

Research on network technologies and software to link researchers and to facilitate movement of large data sets

DOE SciDAC Program

Source: SciDAC web site

DOE SciDAC Program

Several programs under SciDAC Under Advanced Scientific Computing (MICS)

High-End Computer System Performance: PERC And others…

Under High Energy Nuclear Physics (HENP) National Infrastructure for Lattice Gauge Computing

(Lattice QCD) And others…

Several others on Biology, Fusion Energy, Basic Energy, …

SciDAC Lattice QCD

Involves most U.S. lattice theorists funding primarily for software, but also clusters integration of disparate activities software structure for code/data interoperability

Two, complementary hardware approaches commodity clusters at FermiLab and Jefferson Lab QCDOC hardware at Columbia/Brookhaven

Software QMP, communication library optimized for QCD

• Myrinet GM, QCDOC mesh and MPI QLA, lattice-aware single node linear algebra QDP, lattice wide data parallel computations QIO, parallel file I/O optimized inverters

Lattice QCD Quantum Chromodynamics (QCD)

strong interaction between quarks, mediated by gluons Both nuclear physicists and high-energy physicists are involoved PI: Bob Sugar at UCSB

Lattice QCD numerical simulation of QCD via discretized space/time

• quarks at lattice points, with gluons mediating along edges– SU(3) matrix operations dominate the calculation

yields complex, sparse matrices• solution via conjugate gradient techniques

MILC (MIMD Lattice Computation) one lattice QCD implementation http://www.usqcd.org/

Lattice QCD

†1ˆ ˆ ˆ( )

2D x U x x U x x

a

Source: Richard C. Brower & Robert Edwards

Optimized Dirac Operators, InvertersLevel 3

QDP (QCD Data Parallel)

Lattice Wide Operations, Data shifts

Level 2

QMP (QCD Message Passing)

QLA (QCD Linear Algebra)

Level 1

QIO

XML I/ODIME

Lattice QCD Software Plans

C/C++ implementation supports MPI, GM, QCDOC and gigabit Ethernet

C/C++ implementation

Optimized for Pentium 4 and

QCDOC

Source: Richard C. Brower & Robert Edwards

Current Work Application benchmarking

MILC and Chroma(C++) codes Opteron, Intel, Power, SGI, BG/L, QCDOC, Cray, … 10-100/GigE/10-GigE Ethernet, Quadrics, Myrinet, Infiniband

Bottleneck and scalability analysis processor count, cache size, and lattice size

Total cost of ownership power-performance products and scaling

Multiversion code selection CG configuration and tuning Performance optimization

Performance profiling library development