Design and optimization of a portable LQCD Monte Carlo code using OpenACC

Bonati, Claudio; Coscetti, Simone; D’Elia, Massimo; Mesiti, Michele; Negro, Francesco; Calore, Enrico; Schifano, Sebastiano Fabio; Silvi, Giorgio; Tripiccione, R.

doi:10.1142/s0129183117500632

Cited by 21 publications

(23 citation statements)

References 46 publications

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“…The partition function is periodic in b with period N x N y . Numerical simulations have been performed using the Rational Hybrid Monte-Carlo algorithm (RHMC) [126] implemented in the NISSA code [127] and in the Open-StaPLE code for GPUs [128,129]. We have performed around 100 runs with different combinations of T and B for each value of the pion mass, with average statistics of approximately 3000 RHMC trajectories for each run.…”

Section: Methodsmentioning

confidence: 99%

QCD phase diagram in a magnetic background for different values of the pion mass

et al. 2018

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We investigate the behavior of the pseudo-critical temperature of N f = 2+1 QCD as a function of a static magnetic background field for different values of the pion mass, going up to mπ ≃ 660 MeV. The study is performed by lattice QCD simulations, adopting a stout staggered discretization of the theory on lattices with Nt = 6 slices in the Euclidean temporal direction; for each value of the pion mass the temperature is changed moving along a line of constant physics. We find that the decrease of Tc as a function of B, which is observed for physical quark masses, persists in the whole explored mass range, even if the relative variation of Tc appears to be a decreasing function of mπ, approaching zero in the quenched limit. The location of Tc is based on the renormalized quark condensate and its susceptibility; determinations based on the Polyakov loop lead to compatible results. On the contrary, inverse magnetic catalysis, i.e. the decrease of the quark condensate as a function of B in some temperature range around Tc, is not observed when the pion mass is high enough. That supports the idea that inverse magnetic catalysis might be a secondary phenomenon, while the modifications induced by the magnetic background on the gauge field distribution and on the confining properties of the medium could play a primary role in the whole range of pion masses.

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Section: Methodsmentioning

confidence: 99%

QCD phase diagram in a magnetic background for different values of the pion mass

et al. 2018

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“…In these simulations, most of the time is spent in the execution of the so-called Dirac Operator, which is known to be memory-bound. 40 In particular, this benchmark exhibits a double precision operational intensity: I ≈ 0.62.…”

Section: Other Applicationsmentioning

confidence: 99%

Evaluation of DVFS techniques on modern HPC processors and accelerators for energy‐aware applications

Calore

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Schifano

et al. 2017

Concurrency and Computation

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SUMMARYEnergy efficiency is becoming increasingly important for computing systems, in particular for large scale HPC facilities. In this work we evaluate, from an user perspective, the use of Dynamic Voltage and Frequency Scaling (DVFS) techniques, assisted by the power and energy monitoring capabilities of modern processors in order to tune applications for energy efficiency. We run selected kernels and a full HPC application on two high-end processors widely used in the HPC context, namely an NVIDIA K80 GPU and an Intel Haswell CPU. We evaluate the available trade-offs between energy-to-solution and time-to-solution, attempting a function-by-function frequency tuning. We finally estimate the benefits obtainable running the full code on a HPC multi-GPU node, with respect to default clock frequency governors. We instrument our code to accurately monitor power consumption and execution time without the need of any additional hardware, and we enable it to change CPUs and GPUs clock frequencies while running. We analyze our results on the different architectures using a simple energy-performance model, and derive a number of energy saving strategies which can be easily adopted on recent high-end HPC systems for generic applications.

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“…Numerical simulations have been performed on the COKA cluster, using 5 computing nodes, each with 8 NVIDIA K80 dual-GPU boards and two 56 Gb/s FDR InfiniBand network interfaces. Our parallel code (Open-StaPLE) is a single [78] and multi [79] GPU implementation of a standard Rational Hybrid Monte-Carlo algorithm. It is an evolution of a previous CUDA code [80], developed using the OpenACC and OpenMPI frameworks to manage respectively parallelism on the GPUs and among the nodes.…”

Section: Numerical Setupmentioning

confidence: 99%

Roberge-Weiss endpoint and chiral symmetry restoration in Nf=2+1 QCD

et al. 2019

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We investigate the fate of the Roberge-Weiss endpoint transition and its connection with the restoration of chiral symmetry as the chiral limit of N f = 2 + 1 QCD is approached. We adopt a stout staggered discretization on lattices with Nt = 4 sites in the temporal direction; the chiral limit is approached maintaining a constant physical value of the strange-to-light mass ratio and exploring three different light quark masses, corresponding to pseudo-Goldstone pion masses mπ ≃ 100, 70 and 50 MeV around the transition. A finite size scaling analysis provides evidence that the transition remains second order, in the 3D Ising universality class, in all the explored mass range. The residual chiral symmetry of the staggered action also allows us to investigate the relation between the Roberge-Weiss endpoint transition and the chiral restoration transition as the chiral limit is approached: our results, including the critical scaling of the chiral condensate, are consistent with a coincidence of the two transitions in the chiral limit; however we are not able to discern the symmetry controlling the critical behavior, because the critical indexes relevant to the scaling of the chiral condensate are very close to each other for the two possible universality classes (3D Ising or O(2)).

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Design and optimization of a portable LQCD Monte Carlo code using OpenACC

Cited by 21 publications

References 46 publications

QCD phase diagram in a magnetic background for different values of the pion mass

QCD phase diagram in a magnetic background for different values of the pion mass

Evaluation of DVFS techniques on modern HPC processors and accelerators for energy‐aware applications

Roberge-Weiss endpoint and chiral symmetry restoration in Nf=2+1 QCD

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