Konstantin Petrov

Overview of the QCDSP and QCDOC computers

The QCDSP and QCDOC computers are two generations of multithousand-node multidimensional mesh-based computers designed to study quantum chromodynamics (QCD), the theory of the strong nuclear force. QCDSP (QCD on digital signal processors), a four-dimensional mesh machine, was completed in 1998; in that year, it won the Gordon Bell Prize in the price/performance category. Two large installations--of 8,192 and 12,288 nodes, with a combined peak speed of one teraflops--have been in operation since. QCD-on-a-chip (QCDOC) utilizes a sixdimensional mesh and compute nodes fabricated with IBM systemon-a-chip technology. It offers a tenfold improvement in price/ performance. Currently, 100-node versions are operating, and there are plans to build three 12,288-node, 10-teraflops machines. In this paper, we describe the architecture of both the QCDSP and QCDOC machines, the operating systems employed, the user software environment, and the performance of our application-- lattice QCD.

Strong Running Coupling at τ and Z 0 Mass Scales from Lattice QCD

This Letter reports on the first computation, from data obtained in lattice QCD with u, d, s, and c quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the momentum-subtraction Taylor scheme. We provide readers with estimates of α(MS[over ¯])(m(τ)(2)) and α(MS[over ¯])(m(Z)(2)) in very good agreement with experimental results. Including a dynamical c quark makes the needed running of α(MS[over ¯]) safer.

High statistics determination of the strong coupling constant in Taylor scheme and its OPE Wilson coefficient from lattice QCD with a dynamical charm

We are particularly indebted to A. Le Yaouanc, J. P. Leroy, and J. Micheli for participating in many fruitful discussions at the preliminary stages of this work. We thank the support of the Spanish MICINN FPA2011-23781 research project and the IN2P3 (CNRS-Lyon), IDRIS (CNRS-Orsay), TGCC (Bruyes-Le-Chatel), and CINES (Montpellier). K. Petrov is part of the P2IO Laboratory of Excellence.

QCDOC: A 10 Teraflops Computer for Tightly-Coupled Calculations

Numerical simulations of the strong nuclear force, known as quantum chromodynamics or QCD, have proven to be a demanding, forefront problem in high-performance computing. In this report, we describe a new computer, QCDOC (QCD On a Chip), designed for optimal price/performance in the study of QCD. QCDOC uses a six-dimensional, low-latency mesh network to connect processing nodes, each of which includes a single custom ASIC, designed by our collaboration and built by IBM, plus DDR SDRAM. Each node has a peak speed of 1Gigaflops and two 12,288node, 10+ Teraflops machines are to be completed in the fall of 2004. Currently, a 512 node machine is running, delivering efficiencies as high as 45% of peak on the conjugate gradient solvers that dominate our calculations and a 4096-node machine with a cost of

Singlet Free Energies and the Renormalized Polyakov Loop in full QCD

1.6M is under construction. This should give us a price/performance less than

Three-gluon running coupling from lattice QCD at N f = 2 + 1 + 1: a consistency check of the OPE approach

1per sustained Megaflops.

Testing the OPE Wilson coefficient for

We calculate the free energy of a static quark anti-quark pair and the renormalized Polyakov loop in 2+1- and 3- flavor QCD using

A^2

16^3 \times 4

from lattice QCD with a dynamical charm

and

QCDOC: project status and first results

16^3 \times 6