PetaQCD : En Route for the automatic code generation for lattice QCD

International audienceNew computer architectures with various weak and strong characteristics appear with increasing speed. We present our work in progress for the tool-chain aimed at rapid prototyping of the novel dirac matrix inversion algorithms for emerging architectures. From scientific description of the algorithm on the front end to the several back ends we discuss how symbolic manipulation may be used to create and optimize lattice calculations on the fly

An efficient CELL library for lattice quantum chromodynamics

International audienceQuantum chromodynamics (QCD) is the theory of subnuclear physics, aiming at modeling the strong nuclear force, which is responsible for the interactions of nuclear particles. Numerical QCD studies are performed through a discrete formalism called LQCD (Lattice Quantum Chromodynamics). Typical simulations involve very large volume of data and numerically sensitive entities, thus the crucial need of high performance computing systems. We propose a set of CELL-accelerated routines for basic LQCD calculations. Our framework is provided as a unified library and is particularly optimized for an iterative use. Each routine is parallelized among the SPUs, and each SPU achieves it task by looping on small chunk of arrays from the main memory. Our SPU implementation is vectorized with double precision data, and the cooperation with the PPU shows a good overlap between data transfers and computations. Moreover, we permanently keep the SPU context and use mailboxes to synchronize between consecutive calls. We validate our library by using it to derive a CELL version of an existing LQCD package (tmLQCD). Experimental results on individual routines show a significant speedup compare to standard processor, 11 times better than a 2.83 GHz INTEL processor for instance (without SSE). This ratio is around 9 (with QS22 blade) when consider a more cooperative context like solving a linear system of equations (usually referred as Wislon-Dirac inversion). Our results clearly demonstrate that the CELL is a very promising way for high-scale LQCD simulations