Conveners
Algorithms and Machines: Parallel 1F
- Mike Clark (NVIDIA)
Algorithms and Machines: Parallel 2F
- James Osborn (ANL)
Algorithms and Machines: Parallel 8F
- Steve Gottlieb (Indiana University)
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Dr Ran Zhou (Fermilab)23/06/2014, 14:15Algorithms and MachinesTalkElectromagnetic effects play an important role in many phenomena such as isospin symmetry breaking in the hadron spectrum, hadronic contributions to g-2, etc. We have generalized the MILC QCD code to include the electromagnetic field. In this work, we focus on simulations including charged sea quarks using the RHMC algorithm. We explain the algorithm, code performance, and results...Go to contribution page
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Dr Meifeng Lin (Brookhaven National Laboratory)23/06/2014, 14:35Algorithms and MachinesTalkLattice QCD has entered the era of simulations directly at the physical quark masses thanks to the increasing computing power and algorithmic advancement. But the computational cost for such simulations is still extremely high, both for the gauge field generation and the measurements of physical observables. Adaptive multi grid (MG) algorithm has proven to be quite effective in reducing the...Go to contribution page
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Mr Greg McGlynn (Columbia University)23/06/2014, 14:55Algorithms and MachinesTalkWe determine the scaling behavior of the autocorrelation times of observables constructed from the topological charge density on lattices with periodic and open boundary conditions using a series of high-statistics numerical simulations. The autocorrelation functions of such observables turn out to obey a simple differential equation which allows the motion of topological charge in hybrid...Go to contribution page
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Mr Matthias Rottmann (University of Wuppertal)23/06/2014, 15:15Algorithms and MachinesTalkThe overlap lattice discretization of the Dirac operator preserves the important physical property of chiral symmetry, at the expense of requiring much more effort when solving systems with this operator. We present a preconditioning technique based on another lattice discretization, the Wilson-Dirac operator. Recently, close to normal operators have gained popularity in numerical simulations....Go to contribution page
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James Osborn (ANL)23/06/2014, 15:35Algorithms and MachinesTalkI will give an introduction to the FUEL project for lattice field theory code. The code being developed (called "qhmc") was initially targeted for gauge field generation for beyond standard model theories, and is now growing into a more general framework suitable for analysis too. The design is based on using the Lua scripting language as a wrapper for existing lattice field theory...Go to contribution page
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Dr Piotr Korcyl (DESY Zeuthen)23/06/2014, 16:30Algorithms and MachinesTalkWe report on the status of large volume simulations with 2+1 dynamical quarks which are being performed by the CLS collaboration. The algorithmic details include: open boundary conditions, twisted mass reweighting and the rational approximation for the strange quark, whereas the main feature of the simulation strategy is the approach to the physical point along a trajectory of constant trace...Go to contribution page
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Dr M Clark (NVIDIA)23/06/2014, 16:50Algorithms and MachinesTalkThere has been much progress to date in developing scalable sparse linear solver algorithms on GPUs, utilizing well-known mathematical methods such as mixed precision, domain decomposition and pipelining to improve performance, allowing efficient use of large GPU installations such as Blue Waters and Titan. However, there has been less focus on deploying 'mathematically optimal' linear...Go to contribution page
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Dr Alexei Strelchenko (Fermilab)23/06/2014, 17:10Algorithms and MachinesTalkRealization of the Incremental eigCG algorithm for solving Hermitian linear systems with multiple right hand sides on the CUDA platform is reported. In particular, we present details of implementation of the algorithm in the QUDA library. Preliminary performance results are provided.Go to contribution page
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Dr Justin Foley (Microway and Nvidia)23/06/2014, 17:30Algorithms and MachinesTalkWe describe recent additions to the QUDA software library that are aimed at extending strong scaling in multi-GPU lattice calculations. These include the addition of CPU-thread support in order to increase concurrency and improve the overlap of computation and communication in Krylov solver routines, as well as the modifications needed to enable the GPUDirect RDMA feature recently...Go to contribution page
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Dr Nuno Cardoso (NCSA, University of Illinois)23/06/2014, 17:50Algorithms and MachinesTalkIn this work, we present the GPU implementation of the overrelaxation and steepest descent method with Fourier acceleration methods for Laudau and Coulomb gauge fixing using CUDA for SU(N) with N>2. A multi-GPU implementation of the overrelaxation method is also presented using MPI and CUDA. The GPU performance was measured on BlueWaters and compared against the gauge fixing of the CPU MILC code.Go to contribution page
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Ms Ruizi Li (Indiana University)23/06/2014, 18:10Algorithms and MachinesTalkThe conjugate gradient algorithm is among the most essential and time consuming parts of lattice calculations with staggered quarks. We test the performance of dslash, the key step in the CG algorithm, on the Intel Xeon Phi, also known as the many integrated cores (MIC) architecture, with different parallelization strategies using MPI,OpenMP, and the vector processing units (VPUs).Go to contribution page
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Dr Francesco Di Renzo (University of Parma and INFN)27/06/2014, 14:15Algorithms and MachinesTalkIn the context of thimble regularization of lattice field theories we are developing a new simulation algorithm. The main difficulty is to devise a sampling of configurations on a non-trivial manifold, which is defined as the hypersurface formed by the union of all paths of steepest descent of the complex action ending in a given saddle point. The main point with the new algorithm is the...Go to contribution page
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Mr Matthias Puhr (University Regensburg)27/06/2014, 14:35Algorithms and MachinesTalkThe overlap Dirac operator at finite chemical potential can be efficiently computed with the two-sided Lanczos algorithm. Compared with other methods the Lanczos algorithm has the advantage that it takes into account information about the source vector when constructing an approximation to the overlap operator. In order to study transport coefficients in terms of correlators of conserved...Go to contribution page
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Dr Renwick Hudspith (York University)27/06/2014, 14:55Algorithms and MachinesTalkWe provide details of our implementation of a non-linear conjugate gradient method for Landau and Coulomb gauge fixing with Fourier acceleration. We find clear improvement over the Fourier accelerated steepest descent method, with the average time taken for our algorithm to converge to a fixed, high accuracy, being lower by a factor of 2 to 4 for several lattice volumes.Go to contribution page
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Dr Keitaro Nagata (KEK)27/06/2014, 15:15Algorithms and MachinesTalkThe Wilson fermion determinant can be written in the form of a series expansion in fugacity z=exp(mu/T), provided that the eigenmodes of the temporally reduced operator are obtained. Since the calculation of all eigenmodes rapidly becomes prohibitive for larger volumes, we develop a method to calculate only the low-energy eigenmodes of the reduced matrix using a matrix filetering...Go to contribution page
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Mr Matthew Spraggs (University of Southampton)27/06/2014, 15:35Algorithms and MachinesTalkI demonstrate pyQCD, a native Python library providing an extensible API for single-node lattice measurements and simulations. Boost.Python is used to wrap the underlying C++ code and expose an interface to Python for the generation of propagators and configurations, both of which are returned as numpy ndarray types. The library can take advantage of GPU technology by using CUDA where possible...Go to contribution page