# Massively Parallel QCD

## Abstract

The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.

- Authors:

- Publication Date:

- Research Org.:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 940899

- Report Number(s):
- UCRL-JRNL-229921

Journal ID: ISSN 0018-8646; IBMJAE; TRN: US0807241

- DOE Contract Number:
- W-7405-ENG-48

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: IBM Journal of Research and Development, vol. 52, no. 1/2, December 11, 2007, pp. 189; Journal Volume: 52; Journal Issue: 1/2

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 99 GENERAL AND MISCELLANEOUS; ARCHITECTURE; NUCLEAR FORCES; PERFORMANCE; PHYSICS; PROGRAMMING; QUANTUM CHROMODYNAMICS; STRONG INTERACTIONS; SUPERCOMPUTERS

### Citation Formats

```
Soltz, R, Vranas, P, Blumrich, M, Chen, D, Gara, A, Giampap, M, Heidelberger, P, Salapura, V, Sexton, J, and Bhanot, G.
```*Massively Parallel QCD*. United States: N. p., 2007.
Web.

```
Soltz, R, Vranas, P, Blumrich, M, Chen, D, Gara, A, Giampap, M, Heidelberger, P, Salapura, V, Sexton, J, & Bhanot, G.
```*Massively Parallel QCD*. United States.

```
Soltz, R, Vranas, P, Blumrich, M, Chen, D, Gara, A, Giampap, M, Heidelberger, P, Salapura, V, Sexton, J, and Bhanot, G. Wed .
"Massively Parallel QCD". United States.
doi:. https://www.osti.gov/servlets/purl/940899.
```

```
@article{osti_940899,
```

title = {Massively Parallel QCD},

author = {Soltz, R and Vranas, P and Blumrich, M and Chen, D and Gara, A and Giampap, M and Heidelberger, P and Salapura, V and Sexton, J and Bhanot, G},

abstractNote = {The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.},

doi = {},

journal = {IBM Journal of Research and Development, vol. 52, no. 1/2, December 11, 2007, pp. 189},

number = 1/2,

volume = 52,

place = {United States},

year = {Wed Apr 11 00:00:00 EDT 2007},

month = {Wed Apr 11 00:00:00 EDT 2007}

}