Author
Ronald Babich
Bio: Ronald Babich is an academic researcher from Boston University. The author has contributed to research in topics: Quantum chromodynamics & Dirac operator. The author has an hindex of 11, co-authored 29 publications receiving 1002 citations.
Topics: Quantum chromodynamics, Dirac operator, Nucleon, Strange quark, CUDA
Papers
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TL;DR: A new mixed precision approach for Krylov solvers using reliable updates is developed which allows for full double precision accuracy while using only single or half precision arithmetic for the bulk of the computation.
422 citations
TL;DR: An adaptive multigrid solver for application to the non-Hermitian Wilson-Dirac system of QCD is presented, demonstrating that the algorithm nearly eliminates critical slowing down in the chiral limit and that it has weak dependence on the lattice volume.
Abstract: We present an adaptive multigrid solver for application to the non-Hermitian Wilson-Dirac system of QCD. The key components leading to the success of our proposed algorithm are the use of an adaptive projection onto coarse grids that preserves the near null space of the system matrix together with a simplified form of the correction based on the so-called γ5-Hermitian symmetry of the Dirac operator. We demonstrate that the algorithm nearly eliminates critical slowing down in the chiral limit and that it has weak dependence on the lattice volume.
140 citations
TL;DR: In this paper, the authors demonstrate that using a multi-dimensional parallelization strategy and a domain-decomposed preconditioner allows us to scale up to 256 GPUs on the Edge cluster at Lawrence Livermore National Laboratory.
Abstract: Over the past five years, graphics processing units (GPUs) have had a transformational effect on numerical lattice quantum chromodynamics (LQCD) calculations in nuclear and particle physics. While GPUs have been applied with great success to the post-Monte Carlo "analysis" phase which accounts for a substantial fraction of the workload in a typical LQCD calculation, the initial Monte Carlo "gauge field generation" phase requires capability-level supercomputing, corresponding to O(100) GPUs or more. Such strong scaling has not been previously achieved. In this contribution, we demonstrate that using a multi-dimensional parallelization strategy and a domain-decomposed preconditioner allows us to scale into this regime. We present results for two popular discretizations of the Dirac operator, Wilson-clover and improved staggered, employing up to 256 GPUs on the Edge cluster at Lawrence Livermore National Laboratory.
100 citations
13 Nov 2010
TL;DR: The QUDA library as mentioned in this paper provides a package of mixed precision sparse matrix linear solvers for LQCD applications, supporting single GPUs based on NVIDIA's Compute Unified Device Architecture (CUDA).
Abstract: Graphics Processing Units (GPUs) are having a transformational effect on numerical lattice quantum chromo- dynamics (LQCD) calculations of importance in nuclear and particle physics. The QUDA library provides a package of mixed precision sparse matrix linear solvers for LQCD applications, supporting single GPUs based on NVIDIA's Compute Unified Device Architecture (CUDA). This library, interfaced to the QDP++/Chroma framework for LQCD calculations, is currently in production use on the "9g" cluster at the Jefferson Laboratory, enabling unprecedented price/performance for a range of problems in LQCD. Nevertheless, memory constraints on current GPU devices limit the problem sizes that can be tackled. In this contribution we describe the parallelization of the QUDA library onto multiple GPUs using MPI, including strategies for the overlapping of communication and computation. We report on both weak and strong scaling for up to 32 GPUs interconnected by InfiniBand, on which we sustain in excess of 4 Tflops.
92 citations
TL;DR: In this article, the authors presented the leading chiral order results for the matrix elements of the electroweak penguin operators which give the dominant contribution to direct scaling violation in the standard model.
Abstract: We present results for the $\ensuremath{\Delta}S=2$ matrix elements which are required to study neutral kaon mixing in the standard model (SM) and beyond . We also provide leading chiral order results for the matrix elements of the electroweak penguin operators which give the dominant $\ensuremath{\Delta}I=3/2$ contribution to direct $CP$ violation in $K\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ decays. Our calculations were performed with Neuberger fermions on two sets of quenched Wilson gauge configurations at inverse lattice spacings of approximately 2.2 GeV and 1.5 GeV. All renormalizations were implemented nonperturbatively in the regularization-independent/momentum (RI/MOM) scheme, where we accounted for subleading operator product expansion corrections and discretization errors. We find ratios of non-SM to SM matrix elements which are roughly twice as large as in the only other dedicated lattice study of these amplitudes. On the other hand, our results for the electroweak penguin matrix elements are in good agreement with two recent domain-wall fermion calculations. As a by-product of our study, we determine the strange quark mass. Our main results are summarized and discussed in Sec. VII. Within our statistics, we find no evidence for scaling violations.
86 citations
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TL;DR: The rapid evolution of GPU architectures-from graphics processors to massively parallel many-core multiprocessors, recent developments in GPU computing architectures, and how the enthusiastic adoption of CPU+GPU coprocessing is accelerating parallel applications are described.
Abstract: GPU computing is at a tipping point, becoming more widely used in demanding consumer applications and high-performance computing. This article describes the rapid evolution of GPU architectures-from graphics processors to massively parallel many-core multiprocessors, recent developments in GPU computing architectures, and how the enthusiastic adoption of CPU+GPU coprocessing is accelerating parallel applications.
962 citations
Kyoto University1, Brookhaven National Laboratory2, KEK3, Nagoya University4, Université Paris-Saclay5, University of Washington6, University of Connecticut7, University of Bern8, University of Southern Denmark9, Spanish National Research Council10, University of Rome Tor Vergata11, University of Wuppertal12, Forschungszentrum Jülich13, Osaka University14, San Francisco State University15, Indiana University16, Graduate University for Advanced Studies17, American Physical Society18, University of Edinburgh19, University of Southampton20, Aix-Marseille University21, National Chiao Tung University22, Roma Tre University23, Columbia University24, Autonomous University of Madrid25, University of Mainz26
TL;DR: The determination of the light-quark masses, the form factor, and the decay-constant ratio arising in semileptonic $$K \rightarrow \pi $$K→π transition at zero momentum transfer are reported on.
Abstract: We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0), arising in semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK/fpi of decay constants and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)LxSU(2)R and SU(3)LxSU(3)R Chiral Perturbation Theory and review the determination of the BK parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, for this review, we focus on D- and B-meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant alpha_s.
901 citations
Yukawa Institute for Theoretical Physics1, Brookhaven National Laboratory2, Nagoya University3, KEK4, Université Paris-Saclay5, Washington University in St. Louis6, University of Connecticut7, University of Bern8, Spanish National Research Council9, University of Southern Denmark10, University of Rome Tor Vergata11, Forschungszentrum Jülich12, University of Wuppertal13, Osaka University14, San Francisco State University15, Indiana University16, Graduate University for Advanced Studies17, American Physical Society18, University of Edinburgh19, University of Southampton20, Aix-Marseille University21, National Chiao Tung University22, Roma Tre University23, Columbia University24, Autonomous University of Madrid25, University of Washington26, University of Mainz27
TL;DR: The determination of the light-quark masses, the form factor, and the decay constant ratio arising in the semileptonic $$K \rightarrow \pi $$K→π transition at zero momentum transfer are reported on.
Abstract: We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle-physics community. More specifically, we report on the determination of the light-quark masses, the form factor [Formula: see text], arising in the semileptonic [Formula: see text] transition at zero momentum transfer, as well as the decay constant ratio [Formula: see text] and its consequences for the CKM matrix elements [Formula: see text] and [Formula: see text]. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of [Formula: see text] and [Formula: see text] Chiral Perturbation Theory. We review the determination of the [Formula: see text] parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. The latter quantities are an addition compared to the previous review. For the heavy-quark sector, we provide results for [Formula: see text] and [Formula: see text] (also new compared to the previous review), as well as those for D- and B-meson-decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. Finally, we review the status of lattice determinations of the strong coupling constant [Formula: see text].
678 citations
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Kyoto University1, Brookhaven National Laboratory2, KEK3, Université Paris-Saclay4, University of Connecticut5, University of Bern6, University of Regensburg7, University of Southern Denmark8, University of Rome Tor Vergata9, Forschungszentrum Jülich10, University of Wuppertal11, Osaka University12, San Francisco State University13, Indiana University14, Los Alamos National Laboratory15, Graduate University for Advanced Studies16, American Physical Society17, Autonomous University of Madrid18, University of Edinburgh19, University of Southampton20, National Chiao Tung University21, Chung Yuan Christian University22, Columbia University23, University of North Carolina at Chapel Hill24, Trinity College, Dublin25, University of Washington26, Fermilab27, Humboldt University of Berlin28, University of Mainz29
TL;DR: In this article, a review of lattice results related to pion, kaon, D-meson, neutral kaon mixing, B-meon, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities is presented.
Abstract: We review lattice results related to pion, kaon, D-meson, B-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $f_+(0)$ arising in the semileptonic $K \rightarrow \pi $ transition at zero momentum transfer, as well as the decay constant ratio $f_K/f_\pi $ and its consequences for the CKM matrix elements $V_{us}$ and $V_{ud}$. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $SU(2)_L\times SU(2)_R$ and $SU(3)_L\times SU(3)_R$ Chiral Perturbation Theory. We review the determination of the $B_K$ parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $m_c$ and $m_b$ as well as those for D- and B-meson decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant $\alpha _s$. Finally, in this review we have added a new section reviewing results for nucleon matrix elements of the axial, scalar and tensor bilinears, both isovector and flavor diagonal.
607 citations
TL;DR: In this paper, the authors derive upper bounds on the coefficients of the most general ΔF = 2 effective Hamiltonian, and these upper bounds can be translated into lower bounds on new physics that contributes to these low-energy effective interactions.
Abstract: We update the constraints on new-physics contributions to ΔF = 2 processes from the generalized unitarity triangle analysis, including the most recent experimental developments. Based on these constraints, we derive upper bounds on the coefficients of the most general ΔF = 2 effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of new physics that contributes to these low-energy effective interactions. We point out that, due to the enhancement in the renormalization group evolution and in the matrix elements, the coefficients of non-standard operators are much more constrained than the coefficient of the operator present in the Standard Model. Therefore, the scale of new physics in models that generate new ΔF = 2 operators, such as next-to-minimal flavour violation, has to be much higher than the scale of minimal flavour violation, and it most probably lies beyond the reach of direct searches at the LHC.
440 citations