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Simulating Quarks and Gluons with Quantum Chromodynamics. February 10, 2005. CS635 Parallel Computer Architecture. Mahantesh Halappanavar. Impact on Science. LQCD will impact science at all scales. Major Goals: Verify the standard model (discover the limits)
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Simulating Quarks and Gluons with Quantum Chromodynamics February 10, 2005. CS635 Parallel Computer Architecture. Mahantesh Halappanavar.
Impact on Science • LQCD will impact science at all scales. • Major Goals: • Verify the standard model (discover the limits) • Determine properties of interacting matter under extreme conditions • Understand internal structure of nucleons and other strongly interacting particles. • Lattice QCD simulations are essential to research in all of these areas. • Possible only by computation, results needed urgently to support the experimental work (like Relativistic Heavy Ion Collider - BNL)
Scientific Opportunities • With sustained computational power of 100 Tflops/s (currently ~1Tflops) and improved lattice formulations, major advances in our understanding of internal structure of nucleons can be made. • Pflops/s resources would enable study of the gluon structure of the nucleon, in addition to its quark structure. • These calculations would significantly deepen our understanding of the standard model and therefore of the basic laws of physics.
Research Issues • QCD is formulated in the four-dimensional space-time continuum and involves hundreds of millions of variables. • Simulations need to be done at small distances which grows at approximately as the seventh power of the inverse of the lattice spacing. • Up and down quarks have very small mass and therefore cannot be represented accurately (need Pflop/s computational power). • Dirac operator: 70-90% of computations – sparse matrix & iterative techniques. Standard multilevel solver techniques to accelerate inversion cannot be used due to random nature of the nonzero elements of the Dirac operator. • New algorithms needed for QCD at large densities and time dependent problems.
Resources Required: • Need for special type of machines: • Commercial cache based machine: 10-15% • Specially designed: 35-50% • Basic operation: multiplication of a three component vector of complex numbers, by a 3 X 3 matrix of complex numbers. • Critical: relationship between data movement and floating point operations. Regular architectures would prove to be insufficient. • Special machines at FNAL and JLab.
“More Science Per Dollar” • First production three-dimensional mesh computer system in the world. • Prototype 256-node 3-D Gigabit Ethernet mesh Linux cluster arranged in 4X8X8 (torus) configuration using Intel PRO/1000 MT Dual Port Server Adapters as the interconnect. • Intel Xeon processor based node is wired point-to-point to six adjacent nodes using three Intel Cards, eliminating need for a switch. • ~0.7 teraflops sustained, data rates approaching 500 MB/sec/node have been achieved.
Metrics of Success • True success will be generation of new results with accuracies sufficient to advance current understanding of fundamental theory. • Make precise tests on Standard Model and develop more encompassing theory than the Standard Model. • All this is possible when the required computational resources will become available.
