The Tenth International Workshop on Lattice QFT and Numerical Analysis (QCDNA X)

Contribution List

15. HMC: Geometry and Applications

Alessandro Barp

27/06/2017, 09:30

6. Deflation for Monte-Carlo estimation of the trace of a matrix inverse

Mr Eloy Romero Alcalde (College of William and Mary )

27/06/2017, 10:15

Talk

In the context of computing disconnected diagrams, we investigate the
efficient estimation of the trace of large-scale matrix inverses. Our approach
is based on the Hutchinson method (Monte-Carlo averaging over matrix
quadratures). Previous work showed that combining deflation against the lowest
part of the spectrum with Hierarchical Probing can accelerate the convergence
significantly. As...

5. Progress and Challenge of Lattice Quantum Finite Elements (QFE) on Spheres

Dr Richard Brower (Boston University)

27/06/2017, 11:15

Talk

Extending lattice field to ultraviolet complete quantum field theory on any smooth Riemann manifolds is a challenging problem. By adapting element methods (FEM) and Regge geometry one recovers classical (IR) solution in the continuum. However to correctly handle UV divergences requires new counter terms to construct a what we call a "Quantum Finite Elements" (QFE) discrete Lagrangian on...

16. Lattice Quantum Field Theory: Numerical Integration in an Infinite Number of Dimensions

Prof. Anthony Kennedy (Higgs Centre for Theoretical Physics, The University of Edinburgh)

27/06/2017, 14:00

Public Talks

Relativistic Quantum Field Theory (QFT) is the formalism upon which the Standard Model of particle physics is built, and it is remarkably successful and accurate. When the interactions are weak then the techniques of renormalized perturbation theory using Feynman diagrams works beautifully, but when the interactions are strong we have to turn to numerical evaluation of the functional integrals...

14. Lattice QCD with mixed action - Borici-Creutz valence quarks on staggered sea

Subhasish Basak (NISER)

27/06/2017, 15:00

Talk

We used Borici-Creutz fermion to study discrete chiral symmetry breaking
at strong coupling in 2-dim Gross-Neveu model and mass spectra in 2-dim
field theories. Mixed action lattice QCD study with Borici-Creutz valence
quarks on staggered sea quarks is carried out. The counter terms are fixed
nonperturbatively to restore the broken symmetries. The effect of partial
quenching and unitarity...

10. Quark-antiquark excited flux tube

Nuno Cardoso (IST)

27/06/2017, 15:30

Talk

We present color field profiles for some of the first SU(3) gluonic excitations of the flux tube in the presence of a static quark-antiquark pair.

22. DD-αAMG on QPACE 3

Mr Daniel Ritchmann (University of Regensburg ), Mr Peter Georg (University of Regensburg)

27/06/2017, 16:30

Talk

We describe our experiences porting the Regensburg implementation of
the DD-αAMG solver from QPACE 2 to QPACE 3. We first review porting from
the first generation Intel Xeon Phi processor (Knights Corner) to its
successor (Knights Landing). Secondly, we present an overview of
Omni-Path, comparing it to the well-known competitor InfiniBand.
Finally, we present the performance of the code on a...

2. MILC code performance on high end CPU and GPU supercomputer clusters

Ruizi Li

27/06/2017, 17:30

Talk

With recent developments in parallel supercomputing architecture,
many core, multi-core, and GPU processors
are now commonplace resulting in more levels of parallelism, memory
hierarchy, and programming complexity. It has been necessary to adapt
the MILC code to these new processors starting with NVIDIA
GPUs and more recently the Intel Xeon Phi processors. We report on
our efforts to port...

4. Algorithmic advances in NSPT

Dr Mattia Dalla Brida (Universita' di Milano-Bicocca & INFN)

28/06/2017, 09:30

Talk

Numerical stochastic perturbation theory (NSPT) is a powerful tool that allows perturbation expansions in QCD and other interesting theories to be estimated to high order in the interactions. The standard algorithms on which NSPT is based on, however, suffer from several limitations which in practice restrict the potential of these techniques. In this talk I will review the recent algorithmic...

12. Numerical Stochastic Perturbation Theory in $\varphi^4$ Theory

Marco Garofalo (Higgs Centre for Theoretical Physics, The University of Edinburgh)

28/06/2017, 10:15

Talk

Numerical stochastic perturbation theory (NSPT) is a powerful tool for estimating high-order perturbative expansions in lattice field theory. The standard NSPT is based on the Langevin equation. In this contribution, we investigate in $\varphi^4$ theory some alternative methods. In particular, we present a study of the recently proposed Instantaneous Stochastic Perturbation Theory, as well as...

20. Nonperturbative anisotropy calibration in lattice QCD at strong coupling

Helvio Jose Caleiro Vairinhos (Fisica Teorica e Met. Mat.-Inst. Nacional de Invest. Cientif.-Un)

28/06/2017, 11:15

Talk

We propose a simple criterion for the nonperturbative renormalization of the anisotropy coupling in lattice QCD with massless staggered fermions, in the strong coupling limit. We compute numerically and to high precision the renormalised anisotropy, and the analogue of Karsch’s coefficients, using diagrammatic Monte Carlo algorithms and multi-histogram reweighting. We observe a large...

13. Algebraic Multigrid: Theory and Practice

Dr James Brannick

28/06/2017, 11:45

Talk

This talk gives an overview of recent progress made in the design and analysis of algebraic multigrid methods. The focus is on the setup algorithm that automatically constructs the multilevel hierarchy used in the solve phase. A sharp two-grid theory is introduced and then used to derive various quality measures of the coarse spaces constructed by the setup algorithm, based on the ideas of...

21. GPU Computing to the Exascale and Beyond

Dr Kate Clark (NVIDIA)

28/06/2017, 14:00

Public Talks

Talk

With the demise of Denard scaling, it is well known that we cannot go faster for greater throughput, rather we have to go wider. However, with the imminent demise of Moore's Law, there lies continued challenges in reaching and exceeding the Exascale. We discuss how and why GPU computing provides a solution to take computational science to this next level. We consider some of the software...

24. HMC, high level structures and architecture support in Grid

Guido Cossu (The University of Edinburgh)

28/06/2017, 15:00

Talk

I will present the strategies we developed in Grid for the HMC sector, in order to support a variety of behaviours without code replication. I will also discuss the current status of the architecture support in view of the upcoming machines.

23. Analyzing AMA data on 48^3 × 96 lattices

Oliver Witsel

28/06/2017, 15:45

Talk

As an example for analyzing data on RBC-UKQCD's 48^3 x 96 ensemble with physical pions, I investigate correlations between propagator sources placed on the same configuration and discuss options for analyzing this data set to extract the Bs-meson decay constant. The data are generated taking advantage of all-mode averaging (AMA) to reduce the numerical costs.

9. Scaling Multigrid to the Exascale

Dr Kate Clark (NVIDIA)

29/06/2017, 09:30

Talk

Owing to its success in removing the critical slowing down of Dirac linear systems, adaptive multigrid is now a standard solver in the arsenal of tools that the lattice field theorist expects. In this work we report on the latest progress in improving the strong scaling of adaptive multigrid algorithms when running on GPU-accelerated architectures using the QUDA library. Techniques include...

8. Novel Approaches for Staggered Multigrid Algorithms

Evan Weinberg

29/06/2017, 10:15

Talk

Critical slowing down in the fermion sector is a leading obstacle facing the approach to the continuum in lattice gauge theory simulations. Adaptive multigrid ($\alpha$-MG) methods offer a solution to the resulting superlinear growth in the cost of iterative Krylov solves. Ongoing research has suggested that previously developed $\alpha$-MG methods, such as the successful formulation for...

1. An Eigensolver for the Hermitian Dirac Operator with Multigrid Acceleration

Mr Artur Strebel (University of Wuppertal)

29/06/2017, 11:15

Talk

In this talk we present a Davidson type eigensolver combined with the DD-$\alpha$AMG multigrid solver library. The basic Davidson method is adjusted to our multigrid method and the structure of the hermitian Dirac operator in a way that both methods benefit from each other.

We compare the resulting eigensolver with a Chebychev filtered Arnoldi method (PARPACK) and the multi purpose...

11. Local Adaptive Refinement on Lattice Gauge Fields

Mr Edward White, Jr.

29/06/2017, 11:45

Talk

Adaptive Mesh Refinement (AMR) has been widely used in computational fluid dynamics, shock hydrodynamics, astrophysics, turbulence modeling and combustion to improve the performance of algorithms running large, complex problems. The results are often impressive. However, for various reasons which will be discussed, traditional AMR is not directly applicable to lattice QCD. This talk proposes a...

7. An implementation of the DD-$\alpha$AMG multigrid solver on Intel Knights Landing

Mr Daniel Ritchmann (University of Regensburg )

Poster

Talk

We describe our experiences porting the Regensburg implementation of the
DD-$\alpha$AMG solver from the first-generation Intel Xeon Phi processor
(Knights Corner) to its successor (Knights Landing). We present the
performance of the code on a single processor as well as the scaling
behavior on many nodes of QPACE 3, which utilizes Intel's new Omni-Path
fabric.

3. An in-depth evaluation of the Intel Omni-Path network for LQCD applications

Mr Peter Georg (University of Regensburg)

Talk

Several parallel machines on which Lattice LQCD applications are being run utilize a new fabric, Intel Omni-Path. We present an overview of Omni-Path, comparing it to the well-known competitor InfiniBand. In the process of adding support for Omni-Path to our communication library pMR we discovered several insights which we discuss along some general usage recommendations. We substantiate our...