Abstract
We report on salient features of a mixed lattice QCD action using valence Möbius domain-wall fermions solved on the dynamical Nf=2+1+1 highly improved staggered quark sea-quark ensembles generated by the MILC Collaboration. The approximate chiral symmetry properties of the valence fermions are shown to be significantly improved by utilizing the gradient-flow scheme to first smear the highly improved staggered quark configurations. The greater numerical cost of the Möbius domain-wall inversions is mitigated by the highly efficient QUDA library optimized for NVIDIA GPU accelerated compute nodes. We have created an interface to this optimized QUDA solver in Chroma. We provide tuned parameters of the action and performance of QUDA using ensembles with the lattice spacings a≃{0.15,0.12,0.09} fm and pion masses mπ≃{310,220,130} MeV. We have additionally generated two new ensembles with a∼0.12 fm and mπ∼{400,350} MeV. With a fixed flow time of tgf=1 in lattice units, the residual chiral symmetry breaking of the valence fermions is kept below 10% of the light quark mass on all ensembles, mres0.1×ml, with moderate values of the fifth dimension L5 and a domain-wall height M5≤1.3. As a benchmark calculation, we perform a continuum, infinite volume, physical pion and kaon mass extrapolation of FK±/Fπ± and demonstrate our results are independent of flow time and consistent with the FLAG determination of this quantity at the level of less than one standard deviation.
| Original language | English |
|---|---|
| Article number | 054513 |
| Journal | Physical Review D |
| Volume | 96 |
| Issue number | 5 |
| DOIs | |
| State | Published - Sep 1 2017 |
| Externally published | Yes |
Funding
We gratefully acknowledge the MILC Collaboration for use of the dynamical HISQ ensembles . The two new ensembles we generated can be made available to any interested person or group. We thank Carleton DeTar and Doug Toussaint for help compiling and using the milc code at LLNL and understanding how to write source fields from Chroma that can be read by milc for the construction of the mixed-meson correlation functions. We also thank Claude Bernard for useful correspondence regarding scale setting and taste violations with the HISQ action. Part of this work was performed at the Kavli Institute for Theoretical Physics supported by National Science Foundation (NSF) Grant No. PHY-1125915. The software used for this work was built on top of the Chroma software suite and the highly optimized QCD GPU library QUDA . We also utilized the highly efficient HDF5 I/O Library with an interface to HDF5 in the USQCD package that was added with SciDAC 3 support (CalLat) , as well as the milc software for solving for HISQ propagators. Finally, the high performance computing (HPC) jobs were efficiently managed with a bash job manager, metaq , capable of intelligently backfilling idle nodes in sets of nodes bundled into larger jobs submitted to HPC systems. metaq was developed with SciDAC 3 support (CalLat) and is available on github . The numerical calculations in this work were performed at the Jefferson Lab High Performance Computing Center and the Fermilab Lattice Gauge Theory Computational Facility on facilities of the USQCD Collaboration, which are funded by the Office of Science of the U.S. Department of Energy; Lawrence Livermore National Laboratory on the Surface and RZhasGPU GPU clusters as well as the Cab CPU and Vulcan BG/Q clusters; and the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725, on the Titan machine through a DOE Innovative and Novel Computational Impact on Theory and Experiment (INCITE) award (CalLat). We thank the Lawrence Livermore National Laboratory Institutional Computing Grand Challenge program for the computing allocation. This work was performed with support from Laboratory Directed Research and Development (LDRD) funding from LLNL 13-ERD-023 (E. B., E. R., and P. V.) and by the RIKEN Special Postdoctoral Researcher program (E. R.). This work is supported in part by the DFG and the NSFC through funds provided to the Sino-German CRC 110 “Symmetries and the Emergence of Structure in QCD” (E. B.). This work was also performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 (E. B., E. R., and P. V.); under which Jefferson Science Associates, Limited Liability Corporation (LLC), manages and operates Jefferson Lab (B. J. and K. O.) which includes funding from the DOE Office Of Science, Offices of Nuclear Physics, High Energy Physics and Advanced Scientific Computing Research under the SciDAC program (USQCD) (B. J.); under Contract No. DE-AC02-05CH11231, through which the Regents of the University of California manage and operate Lawrence Berkeley National Laboratory and the National Energy Research Scientific Computing Center (C. C. C., T. K., and A. W. L.). This work was further performed under the auspices of the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contracts No. DE-FG02-04ER41302 (C. M. B. and K. N. O.), No. DE-SC00046548 (A. N.), and No. DE-SC0015376, Double-Beta Decay Topical Collaboration (A. W. L.); by the Office of Advanced Scientific Computing Research, Scientific Discovery through Advanced Computing (SciDAC) program under Award No. KB0301052 (E. B., T. K., and A. W. L.); and by the DOE Early Career Research Program, Office of Nuclear Physics under FWP NQCDAWL (C. C. C. and A. W. L.).