openQ*D code: a versatile tool for QCD+QED simulations

Abstract

We present the open-source package openQ*D-1.0 [1], which has been primarily, but not uniquely, designed to perform lattice simulations of QCD+QED and QCD, with and without C * boundary conditions, and O(a) improved Wilson fermions. The use of C * boundary conditions in the spatial direction allows for a local and gauge-invariant formulation of QCD+QED in finite volume, and provides a theoretically clean setup to calculate isospin-breaking and radiative corrections to hadronic observables from first principles. The openQ*D code is based on openQCD-1.6 [2] and NSPT-1.4 [3]. In particular it inherits from openQCD-1.6 several core features, e.g. the highly optimized Dirac operator, the locally deflated solver, the frequency splitting for the RHMC, or the 4th order OMF integrator.

Performance optimizations for porting the openQ$^\star$D package to GPUs

“…Figure 1 shows all the simulated data types using a reduction data type of binary64, meaning that all reduction operations where conducted in binary64 . The following hierarchy is expected (smaller means convergence in fewer steps): (1) where bfloat16 could be either at position (1) or (2), depending on what is more important; precision or number range.…”

“…See line 429ff in modules/linsolv/cgne.c in [2] To produce the plots, the Dirac operator Dop_dble() was extracted in binary64 format from the original code running a simulation of a 4 4 lattice, Schrödinger Functional (SF) boundary conditions (type 1), no C ★ boundary conditions (cstar ) and 1 rank. The first 2000 trajectories were considered thermalisation.…”

“…It depends on all other sub-problems as well, but indirectly. See line 212ff in modules/linsolv/fgcr.c in [2]. The possible data types for ldtype, rdtype and sdtype are binary64 and binary32 .…”

“…The scope of this work is an analysis of the different solver algorithms used in the lattice QFT application openQ*D-1.1 [2]. This software package is used for the generation of fully dynamical QCD+QED gauge configurations with C ★ boundary conditions and 𝑂 (𝑎)-improved Wilson-fermions.…”

Off-shell quark bilinear operator Green’s functions at two loops

“…The set up of [6,7,8] has proved to have had a wide use in a variety of lattice problems involving quark bilinear operators. For instance, a non-exhaustive representation set of recent studies can be found in [11,12,13,14,15,16,17,18].…”