Evaluation of computational and energy performance in matrix multiplication algorithms on CPU and GPU using MKL, cuBLAS and SYCL

Matrix multiplication is fundamental in the backpropagation algorithm used to train deep neural network models. Libraries like Intel's MKL or NVIDIA's cuBLAS implemented new and optimized matrix multiplication techniques that increase performance and reduce computational costs. These techniques can also be implemented in CUDA and SYCL and functions with AVX2 and AVX512 instructions, which have lower performance but better precision. The study compares execution times and power consumption using PAPI and PERF and compares accuracy for different matrix sizes. Comparisons were made on architectures such as third and fourth-generation Intel CPUs and NVIDIA V100 and A100 GPUs. The MKL library showed the best performance with a slight loss of precision, while OpenMP and SYCL on the CPU implementation showed the best accuracy but a loss of performance. On the other hand, the results on GPU showed that cuBLAS with tensor cores had the best performance; however, it had a cost in accuracy. The cuBLAS library without these specialized cores shows minimal performance loss and much higher accuracy. The data obtained on different architectures showed that the CPU could achieve performance close to that obtained on the GPU with increased power consumption. These results are conditional on certain hardware specifications, such as the number of cores, clock frequency, processor generation for the CPU, and the speed and bandwidth of the PCI bus and device architecture (compute capability) for the GPU.Comment: 14 page

J Synchrotron Rad

A high-temperature multi-axial test is carried out to characterize the thermo-mechanical behaviour of a 3D-woven SiC/SiC composite aeronautical part under loads representative of operating conditions. The sample is L-shaped and cut out from the part. It is subjected to severe thermal gradients and a superimposed mechanical load that progressively increases up to the first damage. The sample shape and its associated microstructure, the heterogeneity of the stress field and the limited accessibility to regions susceptible to damage require non-contact imaging modalities. An in situ experiment, conducted with a dedicated testing machine at the SOLEIL synchrotron facility, provides the sample microstructure from computed micro-tomographic imaging and thermal loads from infrared thermography. Experimental constraints lead to non-ideal acquisition conditions for both measurement modalities. This article details the procedure of correcting artefacts to use the volumes for quantitative exploitation (i.e. full-field measurement, model validation and identification). After proper processing, despite its complexity, the in situ experiment provides high-quality data about a part under realistic operating conditions. The influence of the mesostructure on fracture phenomena can be inferred from the tomography in the damaged state. Experiments show that the localization of damage initiation is driven by the geometry, while the woven structure moderates the crack propagation. This study widens the scope of in situ thermo-mechanical experiments to more complex loading states, closer to in-service conditions

Performance Evaluation of a Prototype Distributed NFS Server

International audienceA high-performance file system is normally a key point for large cluster installations, where hundreds or even thousands of nodes frequently need to manage large volumes of data. While most solutions usually make use of dedicated hardware and/or specific distribution and replication protocols , the NFSP (NFS Parallel) project aims at improving performance within a standard NFS client/server system. In this paper we investigate the possibilities of a replica-tion model for the NFS server which is based on Lasy Release Consistency (LRC). A prototype has been built upon the user-level NFSv2 server and a performance evaluation is carried out

Discovery and implications of hidden atomic-scale structure in a metallic meteorite

Iron and its alloys have made modern civilization possible, with metallic meteorites providing one of the human’s earliest sources of usable iron as well as providing a window into our solar system’s billion-year history. Here highest-resolution tools reveal the existence of a previously hidden FeNi nanophase within the extremely slowly cooled metallic meteorite NWA 6259. This new nanophase exists alongside Ni-poor and Ni-rich nanoprecipitates within a matrix of tetrataenite, the uniaxial, chemically ordered form of FeNi. The ferromagnetic nature of the nanoprecipitates combined with the antiferromagnetic character of the FeNi nanophases gives rise to a complex magnetic state that evolves dramatically with temperature. These observations extend and possibly alter our understanding of celestial metallurgy, provide new knowledge concerning the archetypal Fe–Ni phase diagram and supply new information for the development of new types of sustainable, technologically critical high-energy magnets

Readout of a antiferromagnetic spintronics systems by strong exchange coupling of Mn2Au and Permalloy

In antiferromagnetic spintronics, the read-out of the staggered magnetization or Neel vector is the key obstacle to harnessing the ultra-fast dynamics and stability of antiferromagnets for novel devices. Here, we demonstrate strong exchange coupling of Mn2Au, a unique metallic antiferromagnet that exhibits Neel spin-orbit torques, with thin ferromagnetic Permalloy layers. This allows us to benefit from the well-estabished read-out methods of ferromagnets, while the essential advantages of antiferromagnetic spintronics are retained. We show one-to-one imprinting of the antiferromagnetic on the ferromagnetic domain pattern. Conversely, alignment of the Permalloy magnetization reorients the Mn2Au Neel vector, an effect, which can be restricted to large magnetic fields by tuning the ferromagnetic layer thickness. To understand the origin of the strong coupling, we carry out high resolution electron microscopy imaging and we find that our growth yields an interface with a well-defined morphology that leads to the strong exchange coupling.Comment: 9 pages, 5 figure

Impression fonctionnelle : les nouvelles applications des procédés d’impression

This document summarizes nearly 13 years of research and development activity that began with the completion of my PhD. It is organized in three parts with, in the first place, the description of my scientific background. A second part will provide a summary description of the main research results obtained during this period. Finally, several perspectives and proposals for short- and longer-term research projects will be detailed in a final section. The main theme of this report is focused on new applications of printing processes. Indeed, my work focuses mainly on the development of functional systems obtained through the deposition by printing of thin layers of active materials. Efforts have mainly focused on (i) the development of nanometric stable aqueous suspensions involving different functional materials (carbon nanotubes, conductive polymers, spherical metal nanoparticles, metallic nanowires), (ii) the adequacy between the flow properties of these suspensions and the deposition process requirements (inkjet – screen printing – coating – spray), (iii) on the interaction with different flexible substrates (polymer film, cellulosic substrates) and (iv) on the characterization the produced elements performances (print quality, electrical characterization, homogeneity of properties, aging, etc.).Ce document présente de manière synthétique près de 13 années d’activité de recherche et de développement qui ont démarré par la réalisation de mes travaux de doctorat. Il est organisé en trois parties avec, en premier lieu, la description de mon parcours scientifique. Une deuxième partie proposera une description synthétique des principaux résultats de recherche obtenus pendant cette période. Enfin, plusieurs perspectives et propositions de projets de recherche à court et plus long terme seront détaillées dans une dernière partie. Le fil conducteur de ce rapport est centré sur les nouvelles applications des procédés d’impression. En effet, mes travaux s’inscrivent dans le développement de systèmes fonctionnels obtenus grâce au dépôt par impression de couches minces de matériaux actifs. Les efforts se sont principalement concentrés (i) sur le développement de suspensions aqueuses nanométriques stables impliquant différents matériaux fonctionnels (nanotubes de carbone, polymères conducteurs, nanoparticules métalliques sphériques, nano-fils métalliques), (ii) sur l’adéquation entre les propriétés d’écoulement de ces suspensions et les exigences des différents procédés de dépôt envisagés (jet d’encre – sérigraphie – enduction – spray), (iii) sur l’interaction avec différents substrats flexibles (film polymères, substrats cellulosiques) et (iv) sur la caractérisation des performances des éléments produits (qualité d’impression, caractérisation électrique, homogénéité des propriétés, vieillissement, etc.)

Impression fonctionnelle : les nouvelles applications des procédés d’impression

This document summarizes nearly 13 years of research and development activity that began with the completion of my PhD. It is organized in three parts with, in the first place, the description of my scientific background. A second part will provide a summary description of the main research results obtained during this period. Finally, several perspectives and proposals for short- and longer-term research projects will be detailed in a final section. The main theme of this report is focused on new applications of printing processes. Indeed, my work focuses mainly on the development of functional systems obtained through the deposition by printing of thin layers of active materials. Efforts have mainly focused on (i) the development of nanometric stable aqueous suspensions involving different functional materials (carbon nanotubes, conductive polymers, spherical metal nanoparticles, metallic nanowires), (ii) the adequacy between the flow properties of these suspensions and the deposition process requirements (inkjet – screen printing – coating – spray), (iii) on the interaction with different flexible substrates (polymer film, cellulosic substrates) and (iv) on the characterization the produced elements performances (print quality, electrical characterization, homogeneity of properties, aging, etc.).Ce document présente de manière synthétique près de 13 années d’activité de recherche et de développement qui ont démarré par la réalisation de mes travaux de doctorat. Il est organisé en trois parties avec, en premier lieu, la description de mon parcours scientifique. Une deuxième partie proposera une description synthétique des principaux résultats de recherche obtenus pendant cette période. Enfin, plusieurs perspectives et propositions de projets de recherche à court et plus long terme seront détaillées dans une dernière partie. Le fil conducteur de ce rapport est centré sur les nouvelles applications des procédés d’impression. En effet, mes travaux s’inscrivent dans le développement de systèmes fonctionnels obtenus grâce au dépôt par impression de couches minces de matériaux actifs. Les efforts se sont principalement concentrés (i) sur le développement de suspensions aqueuses nanométriques stables impliquant différents matériaux fonctionnels (nanotubes de carbone, polymères conducteurs, nanoparticules métalliques sphériques, nano-fils métalliques), (ii) sur l’adéquation entre les propriétés d’écoulement de ces suspensions et les exigences des différents procédés de dépôt envisagés (jet d’encre – sérigraphie – enduction – spray), (iii) sur l’interaction avec différents substrats flexibles (film polymères, substrats cellulosiques) et (iv) sur la caractérisation des performances des éléments produits (qualité d’impression, caractérisation électrique, homogénéité des propriétés, vieillissement, etc.)

A transmission electron microscopy study of low-strain epitaxial BaTiO 3 grown onto NdScO 3

Ferroelectric materials exhibit a strong coupling between strain and electrical polarization. In epitaxial thin films, the strain induced by the substrate can be used to tune the domain structure. Substrates of rare-earth scandates are sometimes selected for the growth of ferroelectric oxides because of their close lattice match, which allows the growth of low-strain dislocation-free layers. Transmission electron microscopy (TEM) is a frequently used technique for investigating ferroelectric domains at the nanometer-scale. However, it requires to thin the specimen down to electron transparency, which can modify the strain and the electrostatic boundary conditions. Here, we have investigated a 320 nm thick epitaxial layer of BaTiO3 grown onto an orthorhombic substrate of NdScO3 with interfacial lattice strains of −0.45% and −0.05% along the two in-plane directions. We show that the domain structure of the layer can be significantly altered by TEM sample preparation depending on the orientation and the geometry of the lamella. In the as-grown state, the sample shows an anisotropic a/c ferroelastic domain pattern in the direction of largest strain. If a TEM lamella is cut perpendicular to this direction so that strain is released, a new domain pattern is obtained, which consists of bundles of thin horizontal stripes parallel to the interfaces. These stripe domains correspond to a sheared crystalline structure (orthorhombic or monoclinic) with inclined polarization vectors and with at least four variants of polarization. The stripe domains are distributed in triangular-shaped 180° domains where the average polarization is parallel to the growth direction. The influence of external electric fields on this domain structure was investigated using in situ biasing and dark-field imaging in TEM