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...
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...
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...
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...
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.
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...
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...
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...
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...
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...
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.
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...
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...
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.
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...
