arXiv subjects

Nuno Cardoso

Publications and source records attributed to Nuno Cardoso.

42 records · Page 3Linked to original sources

arXiv2011

Finite temperature lattice QCD with GPUs

Graphics Processing Units (GPUs) are being used in many areas of physics, since the performance versus cost is very attractive. The GPUs can be addressed by CUDA which is a NVIDIA's parallel computing architecture. It enables dramatic increases in computing performance by harnessing the power of the GPU. We present a performance comparison between the GPU and CPU with single precision and double precision in generating lattice SU(2) configurations. Analyses with single and multiple GPUs, using CUDA and OPENMP, are also presented. We also present SU(2) results for the renormalized Polyakov loop, colour averaged free energy and the string tension as a function of the temperature.

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arXiv2011

SU(2) Lattice Gauge Theory Simulations on Fermi GPUs

In this work we explore the performance of CUDA in quenched lattice SU(2) simulations. CUDA, NVIDIA Compute Unified Device Architecture, is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU in single and double precision. Analyses with multiple GPUs and two different architectures (G200 and Fermi architectures) are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. We produce codes for the Monte Carlo generation of SU(2) lattice gauge configurations, for the mean plaquette, for the Polyakov Loop at finite T and for the Wilson loop. We also present results for the potential using many configurations ($50\ 000$) without smearing and almost $2\ 000$ configurations with APE smearing. With two Fermi GPUs we have achieved an excellent performance of $200 \times$ the speed over one CPU, in single precision, around 110 Gflops/s. We also find that, using the Fermi architecture, double precision computations for the static quark-antiquark potential are not much slower (less than $2 \times$ slower) than single precision computations.

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arXiv2010

Chromoelectric and chromomagnetic fields for the static gluon-quark-antiquark system

The chromoelectric and chromomagnetic fields, created by a static gluon-quark-antiquark system, are computed in the quenched approximation of lattice QCD, in a $24^3\times 48$ lattice at $β=6.2$. We study two geometries, one with a U shape and another with an L shape. The degenerate case of the two gluon glueball is also studied. This is relevant to understand the microscopic structure of hadrons, in particular of hybrids. This also contributes to understand confinement with flux tubes of the chromoelectric field, and to discriminate between the models of fundamental or adjoint tubes.

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arXiv2010

Colour fields in gauge invariant quenched SU(3) Lattice QCD

he colour fields, created by static sources belonging to different SU(3) representations, from the 3 to the 27, are computed in quenched SU(3) lattice QCD, in a 24^3 x 48 lattice at beta=6.2 and a=0.07261(85) fm. We utilize the technique of generalized Wilson Loops to localize the sources, correlated with plaquettes to measure the respective colour fields. We investigate the Casimir scaling of the fields, measured in the static potentials by Bali. We also study the coherence length, comparing with the dual Ginzburg-Landau approach. With the penetration and coherence lengths we determined the Ginzburg-Landau dimensionless parameter, this result is consistent with a type II superconductor picture, and with an effective dual gluon mass of 0.905 +- 0.163 GeV.

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arXiv2010

Colour fields of the static hybrid gluon-quark-antiquark system

The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a $24^3\times 48$ lattice at $β=6.2$ and $a=0.07261(85)\,fm$. We study two geometries, one with a U shape and another with an L shape. The particular cases of the two gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This also contributes to understand confinement with flux tubes and to discriminate between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.

hep-lat↗

arXiv2010

Lattice SU(2) on GPU's

We discuss the CUDA approach to the simulation of pure gauge Lattice SU(2). CUDA is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU with single precision. Analysis with single and multiple GPU's, using CUDA and OPENMP, are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. Using GPU texture memory and minimizing the data transfers between CPU and GPU, we achieve a speedup of $200\times$ using 2 NVIDIA 295 GTX cards relative to a serial CPU, which demonstrates that GPU's can serve as an efficient platform for scientific computing. With multi-GPU's we are able, in one day computation, to generate 1 000 000 gauge configurations in a $48^4$ lattice with $β=6.0$ and calculate the mean average plaquette. We present results for the mean average plaquette in several lattice sizes for different $β$. Finally we present results for the mean average Polyakov loop at finite temperature.

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