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4. Study of pathways to reduce the energy consumption of the CO2 capture process by absorption-regeneration

Author

Dubois Lionel, Costa Alexis, De Weireld Guy, and Thomas Diane

Subjects
capture du co2, absorption-régénération, solvants aminés, simulations, procédés innovants, Engineering (General). Civil engineering (General), TA1-2040
Abstract

Several industrial sectors, such as for example cement manufacturers and lime producers, produce so-called “unavoidable” CO2 emissions because these ones are intrinsically linked to the industrial process itself (decarbonation of calcium carbonate). In order to reduce these emissions, it is necessary to implement a Carbon Capture, Utilization and/or Storage (CCUS) process chain, whose step of capture, although already technologically mature (especially the absorption-regeneration process using amine(s)-based solvents), leads to very high energy consumption. Three pathways to reduce this consumption have been investigated (experimentally and/or through the development of Aspen PlusTM simulations), namely: (i) upstream of the process thanks to the increase of the flue gas CO2 content (by partial oxy-combustion and/or flue gas recirculation), (ii) within the process (using more efficient and innovative mixtures of solvents such as demixing solutions), and (iii) at the configurational level by using advanced configurations in the capture process. It emerged that the use of a demixing process such as the mixture composed of diethylethanolamine (DEEA) and methylamino-propylamine (MAPA), or the implementation of an advanced process configuration (InterCooling Absorber + Rich Vapor Compression + Rich Solvent Splitting and Preheating, with methyldiethanolamine (MDEA) + piperazine (PZ) as a solvent) are the most energy reducing pathways for the absorption-regeneration process, i.e. more than 40% in comparison with a conventional process using monoethanolamine (MEA). Moreover, from an economical point of view, and compared to a basic configuration with MEA, the demixing technology has the advantage of being able to achieve such energy performance with a more limited investment (CAPEX) (+1.6%) than with advanced process configurations (+8.8%).

Published
2023
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11. Symmetric Block-Cyclic Distribution: Fewer Communications Leads to Faster Dense Cholesky Factorization

Author

Beaumont, Olivier, Duchon, Philippe, Eyraud-Dubois, Lionel, Langou, Julien, Vérité, Mathieu, High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), University of Colorado [Denver], Projet Région Nouvelle-Aquitaine 2018-1R50119 'HPC scalable ecosystem'., ANR-19-CE46-0009,SOLHARIS,Solveurs pour architectures hétérogènes utilisant des supports d'exécution, objectif scalabilité(2019), European Project: 956831,TEXTAROSSA(2021), Eyraud-Dubois, Lionel, Solveurs pour architectures hétérogènes utilisant des supports d'exécution, objectif scalabilité - - SOLHARIS2019 - ANR-19-CE46-0009 - AAPG2019 - VALID, and Towards EXtreme scale Technologies and Accelerators for euROhpc hw/Sw Supercomputing Applications for exascale - TEXTAROSSA - 2021-01-01 - 2024-01-01 - 956831 - VALID

Subjects
[INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

International audience; We consider the distributed Cholesky factorization on homogeneous nodes. Inspired by recent progress on asymptotic lower bounds on the total communication volume required to perform Cholesky factorization, we present an original data distribution, Symmetric Block Cyclic (SBC), designed to take advantage of the symmetry of the matrix. We prove that SBC reduces the overall communication volume between nodes by a factor of square root of 2 compared to the standard 2D blockcyclic distribution. SBC can easily be implemented within the paradigm of task-based runtime systems. Experiments using the Chameleon library over the StarPU runtime system demonstrate that the SBC distribution reduces the communication volume as expected, and also achieves better performance and scalability than the classical 2D block-cyclic allocation scheme in all configurations. We also propose a 2.5D variant of SBC and prove that it further improves the communication and performance benefits.

Published
2022

12. Energy, exergy, economic and environmental (4E) analysis of integrated direct air capture and CO2 methanation under uncertainty

Author

Coppitters, Diederik, Costa, Alexis, Chauvy, Remi, Dubois, Lionel, De Paepe, Ward, Thomas, Diane, De Weireld, Guy, Contino, Francesco, and UCL - SST/IMMC/TFL - Thermodynamics and fluid mechanics

Abstract

Direct Air Capture (DAC) technologies are gaining interest in the concept of carbon utilization and Power-to-Gas (PtG), as the economic valorization of the CO into methane provides a viable pathway to allow DAC systems to mature. However, research on DAC mainly focuses on isolated systems, and the system performance depends on parameters that are highly uncertain. To study the integration of DAC in PtG, we developed a DAC-PtG model, performed an Energy, Exergy, Economic and Environmental (4E) analysis and implemented uncertainty quantification to consider the uncertain environment. The results illustrate that the DAC-PtG system is autothermal when introducing a two-stage mechanical vapor recompression unit at the DAC outlet. The exergy efficiency ranges between 51.3% and 52.6% within 3 standard deviations, for which the uncertainty is driven by the ambient conditions and the uncertain heat of desorption. The methane issued from DAC-PtG has a lower carbon footprint than fossil methane when the carbon footprint of the electricity supply is below or equal to 0.12 kg˙CO˙2-eq /kWh. The Levelized Cost of Synthetic Natural Gas (LCSNG) ranges between 130 €/ MWh and 744 €/ MWh, following an uncertain electricity price and uncertain expenses related to DAC and electrolysis. Therefore, bulk manufacturing, further maturing of these technologies and more demonstration projects are required to reduce the uncertainty of the LCSNG. Future works will consider intermittent renewable energy sources to supply power.

Published
2023

15. Weight Offloading Strategies for Training Large DNN Models

Author

Beaumont, Olivier, Eyraud-Dubois, Lionel, Shilova, Alena, Zhao, Xunyi, Eyraud-Dubois, Lionel, High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Scool (Scool), Inria Lille - Nord Europe, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 (CRIStAL), and Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)

Subjects
Scheduling, Offloading Strategies, [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Training of DNNs, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

The limited memory of GPUs induces serious problems in the training phase of deep neural networks (DNNs). Indeed, with the recent tremendous increase in the size of DNN models, which can now routinely include hundreds of billions or even trillions of parameters, it is impossible to store these models in the memory of a GPU and several strategies have been devised to solve this problem. In this paper, we analyze in detail the strategy that consists in offloading the weights of some model layers from the GPU to the CPU when they are not used. Since the PCI bus bandwidth between the GPU and the CPU is limited, it is crucial to know which layers should be transferred (offloaded and prefetched) and when. We prove that this problem is in general NP-Complete in the strong sense and we propose a lower bound formulation in the form of an Integer Linear Program (ILP). We propose heuristics to select the layers to offload and to build the schedule of data transfers. We show that this approach allows to build near-optimal weight offloading strategies on realistic size DNNs and architectures.

Published
2022

16. A complete biomimetic iron-sulfur cubane redox series

Author

Grunwald, Liam, Clémancey, Martin, Klose, Daniel, Dubois, Lionel, Gambarelli, Serge, Jeschke, Gunnar, Wörle, Michael, Blondin, Geneviève, Mougel, Victor, Department of Chemistry and Applied Biosciences [ETH Zürich] (D-CHAB), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Physiochimie des Métaux (PMB), Laboratoire de Chimie et Biologie des Métaux (LCBM - UMR 5249), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), Conception d’Architectures Moléculaires et Processus Electroniques (CAMPE ), and SYstèmes Moléculaires et nanoMatériaux pour l’Energie et la Santé (SYMMES)

Subjects
Multidisciplinary, Mössbauer spectroscopy, Iron, Coenzymes, [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, all-ferrous cubane, [CHIM.MATE]Chemical Sciences/Material chemistry, iron-sulfur clusters, Hydrocarbons, electrochemistry, Biomimetic Materials, nitrogenase, Nitrogenase, [CHIM]Chemical Sciences, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Oxidation-Reduction, Sulfur
Abstract

Synthetic iron-sulfur cubanes are models for biological cofactors, which are essential to delineate oxidation states in the more complex enzymatic systems. However, a complete series of [Fe4S4]n complexes spanning all redox states accessible by 1-electron transformations of the individual iron atoms (n = 0-4+) has never been prepared, deterring the methodical comparison of structure and spectroscopic signature. Here, we demonstrate that the use of a bulky arylthiolate ligand promoting the encapsulation of alkali-metal cations in the vicinity of the cubane enables the synthesis of such a series. Characterization by EPR, 57Fe Mössbauer spectroscopy, UV-visible electronic absorption, variable-temperature X-ray diffraction analysis, and cyclic voltammetry reveals key trends for the geometry of the Fe4S4 core as well as for the Mössbauer isomer shift, which both correlate systematically with oxidation state. Furthermore, we confirm the S = 4 electronic ground state of the most reduced member of the series, [Fe4S4]0, and provide electrochemical evidence that it is accessible within 0.82 V from the [Fe4S4]2+ state, highlighting its relevance as a mimic of the nitrogenase iron protein cluster., Proceedings of the National Academy of Sciences of the United States of America, 119 (31), ISSN:0027-8424, ISSN:1091-6490

Published
2022

17. Survey on Large Scale Neural Network Training

Author

Gusak, Julia, Cherniuk, Daria, Shilova, Alena, Katrutsa, Alexandr, Bershatsky, Daniel, Zhao, Xunyi, Eyraud-Dubois, Lionel, Shliazhko, Oleh, Dimitrov, Denis, Oseledets, Ivan, Beaumont, Olivier, Skolkovo Institute of Science and Technology [Moscow] (Skoltech), Scool (Scool), Inria Lille - Nord Europe, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 (CRIStAL), Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Auteur indépendant, Artificial Intelligence Research Institute (AIRI), Skolkovo Institute of Science and Technology [Moscow] [Skoltech], Scool [Scool], High-End Parallel Algorithms for Challenging Numerical Simulations [HiePACS], and Artificial Intelligence Research Institute [AIRI]

Subjects
FOS: Computer and information sciences, Computer Science - Machine Learning, Artificial Intelligence (cs.AI), Computer Science - Artificial Intelligence, Machine Learning (cs.LG), [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI]
Abstract

International audience; Modern Deep Neural Networks (DNNs) require significant memory to store weight, activations, and other intermediate tensors during training. Hence, many models don't fit one GPU device or can be trained using only a small per-GPU batch size. This survey provides a systematic overview of the approaches that enable more efficient DNNs training. We analyze techniques that save memory and make good use of computation and communication resources on architectures with a single or several GPUs. We summarize the main categories of strategies and compare strategies within and across categories. Along with approaches proposed in the literature, we discuss available implementations.

Published
2022

21. Toward the Improvement of Silicon-Based Composite Electrodes via an In-Situ Si@C-Graphene Composite Synthesis for Li-Ion Battery Applications.

Author

Mery, Adrien, Chenavier, Yves, Marcucci, Coralie, Benayad, Anass, Alper, John P., Dubois, Lionel, Haon, Cédric, Boime, Nathalie Herlin, Sadki, Saïd, and Duclairoir, Florence

Subjects
LITHIUM-ion batteries, HYBRID materials, ELECTRODES, GRAPHENE, HYDROGELS, GREENHOUSE gases
Abstract

Using Si as anode materials for Li-ion batteries remain challenging due to its morphological evolution and SEI modification upon cycling. The present work aims at developing a composite consisting of carbon-coated Si nanoparticles (Si@C NPs) intimately embedded in a three-dimensional (3D) graphene hydrogel (GHG) architecture to stabilize Si inside LiB electrodes. Instead of simply mixing both components, the novelty of the synthesis procedure lies in the in situ hydrothermal process, which was shown to successfully yield graphene oxide reduction, 3D graphene assembly production, and homogeneous distribution of Si@C NPs in the GHG matrix. Electrochemical characterizations in half-cells, on electrodes not containing additional conductive additive, revealed the importance of the protective C shell to achieve high specific capacity (up to 2200 mAh.g−1), along with good stability (200 cycles with an average Ceff > 99%). These performances are far superior to that of electrodes made with non-C-coated Si NPs or prepared by mixing both components. These observations highlight the synergetic effects of C shell on Si NPs, and of the single-step in situ preparation that enables the yield of a Si@C-GHG hybrid composite with physicochemical, structural, and morphological properties promoting sample conductivity and Li-ion diffusion pathways. [ABSTRACT FROM AUTHOR]

Published
2023
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24. An Integer Linear Programming Approach for Pipelined Model Parallelism

Author

Beaumont, Olivier, Eyraud-Dubois, Lionel, Shilova, Alena, Beaumont, Olivier, High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Scool (Scool), Inria Lille - Nord Europe, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189 (CRIStAL), Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS), and Inria

Subjects
Integer Linear Programming, [INFO.INFO-AI] Computer Science [cs]/Artificial Intelligence [cs.AI], Model Parallelism, Memory, [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Training, Parallélisme de modèle, Programmation linéaire en nombres entiers, Mémoire, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Apprentissage, [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI]
Abstract

The training phase in Deep Neural Networks has become an important source of computing resource usage and because of the resulting volume of computation, it is crucial to perform it efficiently on parallel architectures. Even today, data parallelism is the most widely used method, but the associated requirement to replicate all the weights on the totality of computation resources poses problems of memory at the level of each node and of collective communications at the level of the platform. In this context, the model parallelism, which consists in distributing the different layers of the network over the computing nodes, is an attractive alternative. Indeed, it is expected to better distribute weights (to cope with memory problems) and it does not imply large collective communications since only forward activations are communicated. However, to be efficient, it must be combined with a pipelined/streaming approach, which leads in turn to new memory costs. The goal of this paper is to model these memory costs in detail and to show that it is possible to formalize this optimization problem as an Integer Linear Program (ILP)., La phase d’apprentissage dans les réseaux neuronaux profonds est devenue une source importante d’utilisation des ressources de calcul et, en raison du volume de calcul qui en résulte, il est crucial de l’exécuter efficacement sur des architectures parallèles. Aujourd’hui encore, le parallélisme de données est la méthode la plus utilisée, mais l’exigence associée de répliquer tous les poids sur la totalité des ressources de calcul pose des problèmes de mémoire au niveau de chaque nœud et de communications collectives au niveau de la plateforme. Dans ce contexte, le parallélisme de modèle, qui consiste à répartir les différentes couches du réseau sur les nœuds de calcul, est une alternative intéressante. En effet, il est censé mieux répartir les poids (pour faire face aux problèmes de mémoire) et il n’implique pas de grosses communications collectives puisque seules les activations "forward" sont communiquées. Cependant, pour être efficace, elle doit être combinée avec une approche pipelinée/streaming, ce qui entraîne à son tour de nouveaux coûts mémoire. L’objectif de cet article est de modéliser ces coûts de mémoire en détail et de montrer qu’il est possible de formaliser ce problème d’optimisation comme un programme linéaire en nombre entier (ILP).

Published
2022

25. Efficient Combination of Rematerialization and Offloading for Training DNNs

Author

Beaumont, Olivier, Eyraud-Dubois, Lionel, Shilova, Alena, High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, and Beaumont, Olivier

Subjects
[INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

International audience; Rematerialization and offloading are two well known strategies to save memory during the training phase of deep neural networks, allowing data scientists to consider larger models, batch sizes or higher resolution data. Rematerialization trades memory for computation time, whereas Offloading trades memory for data movements. As these two resources are independent, it is appealing to consider the simultaneous combination of both strategies to save even more memory. We precisely model the costs and constraints corresponding to Deep Learning frameworks such as PyTorch or Tensorflow, we propose optimal algorithms to find a valid sequence of memory-constrained operations and finally, we evaluate the performance of proposed algorithms on realistic networks and computation platforms. Our experiments show that the possibility to offload can remove one third of the overhead of rematerialization, and that together they can reduce the memory used for activations by a factor 4 to 6, with an overhead below 20%.

Published
2021

27. Independent tasks on 2 resources with co-scheduling effects

Author

Eyraud-Dubois, Lionel, Bentes, Cristiana, Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Universidade do Estado do Rio de Janeiro [Rio de Janeiro] (UERJ), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest, and Eyraud-Dubois, Lionel

Subjects
Software_OPERATINGSYSTEMS, GPU Concurrency, Scheduling, TheoryofComputation_ANALYSISOFALGORITHMSANDPROBLEMCOMPLEXITY, [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Preemption, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

Concurrent kernel execution is a relatively new feature in modern GPUs, which was designed to improve hardware utilization and the overall system throughput. However, the decision on the simultaneous execution of tasks is performed by the hardware with a leftover policy, that assigns as many resources as possible for one task and then assigns the remaining resources to the next task. This can lead to unreasonable use of resources. In this work, we tackle the problem of co-scheduling for GPUs with and without preemption, with the focus on determining the kernels submission order to reduce the number of preemptions and the kernels makespan, respectively. We propose a graph-based theoretical model to build preemptive and non-preemptive schedules. We show that the optimal preemptive makespan can be computed by solving a Linear Program in polynomial time, and we propose an algorithm based on this solution which minimizes the number of preemptions. We also propose an algorithm that transforms a preemptive solution of optimal makespan into a non-preemptive solution with the smallest possible preemption overhead. We show, however, that finding the minimal amount of preemptions among all preemptive solutions of optimal makespan is a NP-hard problem, and computing the optimal non-preemptive schedule is also NP-hard. In addition, we study the non-preemptive problem, without searching first for a good preemptive solution, and present a Mixed Integer Linear Program solution to this problem. We performed experiments on real-world GPU applications and our approach can achieve optimal makespan by preempting 6 to 9% of the tasks. Our non-preemptive approach, on the other side, obtains makespan within 2.5% of the optimal preemptive schedules, while previous approaches exceed the preemptive makespan by 5 to 12%.

Published
2020

28. A complete biomimetic iron-sulfur cubane redox series

Author

Grunwald, Liam, Clémancey, Martin, Klose, Daniel, Dubois, Lionel, Gambarelli, Serge, Jeschke, Gunnar, Wörle, Michael, Blondin, Geneviève, and Mougel, Victor

Abstract

Synthetic iron-sulfur cubanes are essential models for biological cofactors in the more complex enzymatic environments. However, a complete series of [Fe4S4]n complexes spanning all biorelevant oxidation states (n = 0-3+) has never been prepared. Here, we demonstrate that the use of a bulky arylthiolate ligand promoting the encapsulation of alkali-metal cations in the vicinity of the cubane enables the synthesis of such a series. Characterization by EPR, 57Fe Mössbauer spectroscopy, UV-Vis electronic absorption and variable-temperature X-ray diffraction analysis reveals key trends for the Fe4S4 core’s geometry as well as for the Mössbauer isomer shift, which both correlate systematically with oxidation state. Furthermore, we confirm the S=4 electronic ground state of the most reduced member, [Fe4S4]0, in agreement with that proposed for the all-ferrous cubanes in Nature., ChemRxiv

Published
2021
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29. Life cycle and techno‐economic assessments of direct air capture processes: An integrated review.

Author

Chauvy, Remi and Dubois, Lionel

Subjects
*PRODUCT life cycle assessment, *WASTE heat, *CARBON emissions, *CARBON offsetting, *SYNTHETIC fuels, *ECONOMIC indicators
Abstract

Summary: To limit the increase of the global average temperature in the range of 1.5°C to 2°C above pre‐industrial levels, it is mandatory to reduce anthropogenic CO2 emissions. Aggressive mitigation measures are thus needed to tackle these emissions leading to "net negative CO2 emissions." The present study focuses on direct air capture (DAC) processes among the diverse negative emissions approaches. DAC refers to man‐made technologies that selectively extract CO2 from ambient air and deliver it in a concentrated form for further use or storage. DAC technologies are currently developed at different levels of maturity and performance. They can be classified into three main approaches, the liquid sorbent approach, the solid sorbent approach, and a panel of more innovative technologies combining different approaches. They involve various unit operations and different materials and energy types (electrical and thermal). To better evaluate the status and both the environmental and economic performances, the present paper provides a literature review of the life cycle (LCA) and techno‐economic (TEA) assessments in relation to DAC process chains. It was emphasized that DAC could lead to negative emissions if paired with subsequent storage, while the production of synthetic fuels can at best be carbon neutral when using CO2 from the air. Building large DAC plants has an impact on the amount of energy required to operate them, as well as other environmental impacts with regard to land, water, and material use. Even if the carbon‐negative characteristic of DAC was confirmed, these technologies are still expensive. It was highlighted that large DAC costs ranges are currently provided in the literature, from €80/tCO2 to €1133/tCO2 for the current DAC processes, while estimations from €34 to €260/tCO2 are expected in the future. Different levers were identified to improve the environmental and economic performances of DAC processes, such as the availability of waste heat, the heat integration possibilities, and, among others, the improvement of contactors and sorbents properties. Highlights: The paper entitled "Life cycle and techno‐economic assessments of direct air capture processes: An integrated review," submitted by Dr Remi Chauvy and Dr Lionel Dubois, fills the current gap in terms of comprehensive systematic and impacts assessment research on Direct Air Capture (DAC) technologies.Indeed, to better evaluate the status and both the environmental and economic performances of DAC technologies, the present paper provides an up‐to‐date literature review of the life cycle (LCA) and techno‐economic (TEA) assessments in relation with DAC process chains.The paper goes beyond the literature review as key levers, related to technology developments, to the energy use and to the implementation characteristics, are also identified to improve the environmental and economic performances of DAC processes. [ABSTRACT FROM AUTHOR]

Published
2022
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30. Optimal checkpointing for heterogeneous chains: how to train deep neural networks with limited memory

Author

Herrmann, Julien, Beaumont, Olivier, Eyraud-Dubois, Lionel, Hermann, Julien, Joly, Alexis, and Shilova, Alena

Subjects
FOS: Computer and information sciences, Computer Science - Machine Learning, Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Neural and Evolutionary Computing, Distributed, Parallel, and Cluster Computing (cs.DC), Neural and Evolutionary Computing (cs.NE), Machine Learning (cs.LG)
Abstract

This paper introduces a new activation checkpointing method which allows to significantly decrease memory usage when training Deep Neural Networks with the back-propagation algorithm. Similarly to checkpoint-ing techniques coming from the literature on Automatic Differentiation, it consists in dynamically selecting the forward activations that are saved during the training phase, and then automatically recomputing missing activations from those previously recorded. We propose an original computation model that combines two types of activation savings: either only storing the layer inputs, or recording the complete history of operations that produced the outputs (this uses more memory, but requires fewer recomputations in the backward phase), and we provide an algorithm to compute the optimal computation sequence for this model. This paper also describes a PyTorch implementation that processes the entire chain, dealing with any sequential DNN whose internal layers may be arbitrarily complex and automatically executing it according to the optimal checkpointing strategy computed given a memory limit. Through extensive experiments, we show that our implementation consistently outperforms existing checkpoint-ing approaches for a large class of networks, image sizes and batch sizes.

Published
2019

31. NMR study of optically active monosubstituted cryptophanes and their interaction with xenon

Author

Huber, J. Gaspard, Dubois, Lionel, Desvaux, Herve, Dutasta, Jean-Pierre, Brotin, Thierry, and Berthault, Patrick

Subjects
Thermodynamics -- Research, Xenon -- Chemical properties, Nuclear magnetic resonance spectroscopy -- Usage, Chemicals, plastics and rubber industries
Abstract

The study of the interaction between xenon and two cryptophane derivatives in organic solution is carried out. The results clearly indicate that in the design of new cage molecules for biosensing, the separation of cryptophane diastereomers is important because their affinity and their properties vis-a-vis could be strongly different.

Published
2004

32. Dynamics of xenon inside hydrophobic cavities as probed by NMR relaxation of dissolved laser-polarized xenon

Author

Dubois, Lionel, Parres, Sandra, Huber, J.Gaspard, Berthault, Patrick, and Desvaux, Herve

Subjects
Chemistry, Physical and theoretical -- Research, Hydrophobic effect -- Research, Xenon -- Magnetic properties, Xenon -- Research, Xenon -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

Longitudinal relaxation times T(sub 1) of laser-polarized xenon in water solutions containing alpha-cylodextrin and wheat nonspecific lipid transfer protein are measured. It reveals that even with an atom of high polarizability, such as xenon, the van der Waals energy is not sufficiently predominant to avoid large amplitude motions of an apolar guest around its average sites.

Published
2004

33. Fast Approximation Algorithms for Task-Based Runtime Systems

Author

BEAUMONT, Olivier, EYRAUD-DUBOIS, Lionel, KUMAR, Suraj, Reformulations based algorithms for Combinatorial Optimization (Realopt), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), STatic Optimizations, Runtime Methods (STORM), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, ANR-13-MONU-0007,SOLHAR,Solveurs pour architectures hétérogènes utilisant des supports d'exécution(2013), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, and Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest

Subjects
List scheduling, Runtime systems, Heterogeneous scheduling, Dense linear algebra, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], Approximation proofs
Abstract

International audience; In High Performance Computing, heterogeneity is now the norm with specialized accelerators like GPUs providing efficient computational power. Resulting complexity led to the development of task-based runtime systems, where complex computations are described as task graphs, and scheduling decisions are made at run-time to perform load balancing between all resources of the platforms. Developing good scheduling strategies, even at the scale of a single node, and analyzing them both theoretically and in practice is expected to have a very high impact on the performance of current HPC systems. The special case of two kinds of resources, typically CPUs and GPUs is already of great practical interest. The scheduling policy Hetero-Prio has been proposed in the context of fast multipole computations (FMM), and has been extended to general task graphs with very promising results. In this paper, we provide a theoretical study of the performance of HeteroPrio, by proving approximation bounds compared to the optimal schedule, both in the case of independent tasks and in the case of general task graphs. Interestingly, our results establish that spoliation (a technique that enables resources to restart uncompleted tasks on another resource) is enough to prove bounded approximation ratios for a list scheduling algorithm on two unrelated resources, which is known to be impossible otherwise. This result holds true both for independent and dependent tasks graphs. Additionally, we provide an experimental evaluation of HeteroPrio on real task graphs from dense linear algebra computation, that establishes its strong performance in practice.

Published
2018

34. West Indian mythology and its literary illustrations

Author

Corzani, Jack and Dubois, Lionel

Subjects
Caribbean Sea -- Social aspects, Mythology -- Analysis -- Social aspects, Myth -- Analysis -- Social aspects, Literature/writing, Social aspects, Analysis
Abstract

'Mythology is the collection of myths of a people, a civilization, a religion.' Those myths may vary from the cosmogonic to the historic (from the transfiguration of a feat of [...]

Published
1994

35. Scheduling on Two Types of Resources: A Survey.

Author

BEAUMONT, OLIVIER, CANON, LOUIS-CLAUDE, EYRAUD-DUBOIS, LIONEL, LUCARELLI, GIORGIO, MARCHAL, LORIS, MOMMESSIN, CLÉMENT, SIMON, BERTRAND, and TRYSTRAM, DENIS

Abstract

The evolution in the design of modern parallel platforms leads to revisit the scheduling jobs on distributed heterogeneous resources. The goal of this survey is to present the main existing algorithms, to classify them based on their underlying principles, and to propose unified implementations to enable their fair comparison, in terms of running time and quality of schedules, on a large set of common benchmarks that we made available for the community. Beyond this comparison, our goal is also to understand the main difficulties that heterogeneity conveys and the shared principles that guide the design of efficient algorithms. [ABSTRACT FROM AUTHOR]

Published
2021
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36. Sizing and Partitioning Strategies for Burst-Buffers to Reduce IO Contention

Author

Aupy, Guillaume, Beaumont, Olivier, Eyraud-Dubois, Lionel, Topology-Aware System-Scale Data Management for High-Performance Computing (TADAAM), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Reformulations based algorithms for Combinatorial Optimization (Realopt), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, 'Investments for the future' Program IdEx Bordeaux – SysNum (ANR-10-IDEX-03-02), Inria, and ANR-17-CE25-0004,DASH,Ordonnancement de données pour le calcul haute-performance(2017)

Subjects
[INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

Burst-Buffers are high throughput and small size storage which are being used as an intermediate storage between the Parallel File System (Parallel File System) and the computational nodes of modern HPC systems. They can allow to hinder to contention to the Parallel File System, a shared resource whose read and write performance increase slower than processing power in HPC systems. A second usage is to accelerate data transfers and to hide the latency to the Parallel File System. In this paper, we concentrate on the first usage. We propose a model for Burst-Buffers and application transfers.We consider the problem of dimensioning and sharing the Burst-Buffers between several applications. This dimensioning can be done either dynamically or statically. The dynamic allocation considers that any application can use any available portion of the Burst-Buffers. The static allocation considers that when a new application enters the system, it is assigned some portion of the Burst-Buffers which cannot be used by the other applications until that application leaves the system and its data is purged from it. We show that the general sharing problem to guarantee fair performance for all applications is an NP-Complete problem. We give a polynomial time algorithms for the special case of finding the optimal buffer size such that no application is slowed down due to Parallel File System contention, both in the static and dynamic cases. Finally, we provide evaluations of our algorithms in realistic settings. We use those to discuss how to minimize the overhead of the static allocation of buffers compared to the dynamic allocation.; Nous nous intéressons à l’utilisation de Burst-Buffers en temps qu’espace de stockage intermédiaire entre les nœuds de calcul et le Système de Fichiers Parallèles (PFS). Ce dimensionnement peut être statique (à l’arrivée d’une application dans le système), ou dynamique (en fonction des demandes Entrées-Sorties).Nous montrons que le problème général de partager équitablement les buffers entre applications est NP-complet. Nous montrons que dans le cas particulier où l’on cherche à minimiser la taille totale du buffer pour qu’aucune application ne soit ralentie est résolvable en temps polynomial. Pour résoudre ce problème nous proposons un programme linéaire.Finalement nous proposons des évaluations à taille de buffer fixé pour montrer la performance de certains algorithmes naifs communs.

Published
2018

37. Point-to-point and congestion bandwidth estimation: experimental evaluation on PlanetLab

Author

Eyraud-Dubois, Lionel, Uznanski, Przemyslaw, Eyraud-Dubois, Lionel, Infrastructures matérielles et logicielles pour la société numérique - Simulation de systèmes de prochaine génération - - SONGS2011 - ANR-11-INFR-0013 - INFRA - VALID, Algorithmics for computationally intensive applications over wide scale distributed platforms (CEPAGE), Université Sciences et Technologies - Bordeaux 1-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), ANR-11-INFR-0013,SONGS,Simulation de systèmes de prochaine génération(2011), Université Sciences et Technologies - Bordeaux 1 (UB)-Inria Bordeaux - Sud-Ouest, and Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

In large scale Internet platforms, measuring the available bandwidth between nodes of the platform is difficult and costly. However, having access to this information allows to design clever algorithms to optimize resource usage for some collective communications, like broadcasting a message or organizing master/slave computations. In this paper, we analyze the feasibility to provide estimations, based on a limited number of measurements, for the point-to-point available bandwidth values, and for the congestion which happens when several communications take place at the same time. We present a dataset obtained with both types of measurements performed on a set of nodes from the PlanetLab platform. We show that matrix factorization techniques are quite efficient at predicting point-to-point available bandwidth, but are not adapted for congestion analysis. However, a LastMile modeling of the platform allows to perform congestion predictions with a reasonable level of accuracy, even with a small amount of information, despite the variability of the measured platform.

Published
2013

38. Comparison of Static and Dynamic Resource Allocation Strategies for Matrix Multiplication

Author

Beaumont, Olivier, Eyraud-Dubois, Lionel, Guermouche, Abdou, Lambert, Thomas, Beaumont, Olivier, Modèles Numériques - Solveurs pour architectures hétérogènes utilisant des supports d'exécution - - SOLHAR2013 - ANR-13-MONU-0007 - MN - VALID, Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), Reformulations based algorithms for Combinatorial Optimization (Realopt), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, ANR-13-MONU-0007,SOLHAR,Solveurs pour architectures hétérogènes utilisant des supports d'exécution(2013), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Institut de Mathématiques de Bordeaux (IMB), Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Segalen - Bordeaux 2-Université Sciences et Technologies - Bordeaux 1-Institut Polytechnique de Bordeaux (Bordeaux INP)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, and Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest

Subjects
static scheduling, runtime scheduling, [INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], dynamic scheduling, Matrix Multiplication, hybrid strategies
Abstract

International audience; The tremendous increase in the size and heterogeneity of supercomputers makes it very difficult to predict the performance of a scheduling algorithm. In this context, relying on purely static scheduling and resource allocation strategies, that make scheduling and allocation decisions based on the dependency graph and the platform description, is expected to lead to large and unpredictable makespans whenever the behavior of the platform does not match the predictions. For this reason, the common practice in most runtime libraries is to rely on purely dynamic scheduling strategies, that make short-sighted scheduling decisions at runtime based on the estimations of the duration of the different tasks on the different available resources and on the state of the machine. In this paper, we consider the special case of Matrix Multiplication, for which a number of static allocation algorithms to minimize the amount of communications have been proposed. Through a set of extensive simulations, we analyze the behavior of static, dynamic, and hybrid strategies, and we assess the possible benefits of introducing more static knowledge and allocation decisions in runtime libraries.

Published
2015

39. Recent Advances in Matrix Partitioning for Parallel Computing on Heterogeneous Platforms.

Author

Beaumont, Olivier, Becker, Brett A., DeFlumere, Ashley, Eyraud-Dubois, Lionel, Lambert, Thomas, and Lastovetsky, Alexey

Subjects
CLOUD computing, APPROXIMATION algorithms, MATRICES (Mathematics), TOPOLOGY, COMMUNICATION
Abstract

The problem of partitioning dense matrices into sets of sub-matrices has received increased attention recently and is crucial when considering dense linear algebra and kernels with similar communication patterns on heterogeneous platforms. The problem of load balancing and minimizing communication is traditionally reducible to an optimization problem that involves partitioning a square into rectangles. This problem has been proven to be NP-Complete for an arbitrary number of partitions. In this paper, we present recent approaches that relax the restriction that all partitions be rectangles. The first approach uses an original mathematical technique to find the exact optimal partitioning. Due to the complexity of the technique, it has been developed for a small number of partitions only. However, even at a small scale, the optimal partitions found by this approach are often non-rectangular and sometimes non-intuitive. The second approach is the study of approximate partitioning methods utilizing recursive partitioning algorithms. In particular we use the work on optimal partitioning to improve pre-existing algorithms. In this paper we discuss the different perspectives this approach opens and present two algorithms, SNRPP which is a $\sqrt{\frac{3}{2}}$ approximation, and NRPP which is a $\frac{2}{\sqrt{3}}$ approximation. While sub-optimal, the NRRP approach works for an arbitrary number of partitions. We use the first exact approach to analyse how close to the known optimal solutions the NRRP algorithm is for small numbers of partitions. [ABSTRACT FROM AUTHOR]

Published
2019
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40. Bedibe: Datasets and Software Tools for Distributed Bandwidth Prediction

Author

Eyraud-Dubois, Lionel, Uznanski, Przemyslaw, Algorithmics for computationally intensive applications over wide scale distributed platforms (CEPAGE), Université Sciences et Technologies - Bordeaux 1-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), Nicolas Hanusse and Fabien Mathieu, ANR-11-INFR-0013,SONGS,Simulation de systèmes de prochaine génération(2011), Eyraud-Dubois, Lionel, Infrastructures matérielles et logicielles pour la société numérique - Simulation de systèmes de prochaine génération - - SONGS2011 - ANR-11-INFR-0013 - INFRA - VALID, Université Sciences et Technologies - Bordeaux 1 (UB)-Inria Bordeaux - Sud-Ouest, and Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

National audience; Pouvoir prédire la bande passante disponible est une problématique cruciale pour un grand nombre d'applications distribuées sur Internet. Plusieurs solutions ont été proposées, mais l'absence d'implémentations communes et de jeux de données reconnus rend difficile la comparaison et la reproductibilité des résultats. Dans cet article, nous présentons bedibe, la combinaison de mesures de bande passante effectuées sur Planet-Lab et d'un logiciel pour faciliter l'écriture et l'étude d'algorithmes pour la prédiction de bande passante. bedibe inclut les implémentations des meilleures solutions de la littérature, et a pour but de faciliter la comparaison des résultats obtenus par les différentes équipes qui travaillent sur ce thème.

Published
2012

41. Online Allocation of Splitable Clients to Multiple Servers on Large Scale Heterogeneous Platforms

Author

Beaumont, Olivier, Eyraud-Dubois, Lionel, Rejeb, Hejer, Thraves, Christopher, Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB), Algorithmics for computationally intensive applications over wide scale distributed platforms (CEPAGE), INRIA Futurs, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), Institut National de Recherche en Informatique et en Automatique (Inria), Université Sciences et Technologies - Bordeaux 1-Inria Bordeaux - Sud-Ouest, Chaintreau, Augustin and Magnien, Clemence, Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Inria Bordeaux - Sud-Ouest, Thraves Caro, Chrsitopher, and Chaintreau, Augustin and Magnien, Clemence

Subjects
[INFO.INFO-DC] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

International audience; Dans cet article, nous considérons l'allocation dynamique (online) d'un très grand nombre de tâches identiques et indépendantes sur une plate-forme maîtres-esclaves. Initialement, plusieurs nœuds maîtres possèdent ou génèrent les tâches qui sont ensuite transférées et traitées par des nœuds esclaves. L'objectif est de maximiser le débit (i.e., le nombre fractionnaire de tâches qui peut être traité en une unité de temps, en régime permanent, par la plate-forme). Nous considérons que les communications se déroulent suivant le modèle multi-port à degré borné, dans lequel plusieurs communications peuvent avoir lieu simultanément sous réserve qu'aucune bande passante ne soit dépassée et qu'aucun serveur n'ouvre simultanément un nombre de connections supérieur à son degré maximal. Sous ce modèle, la maximisation du débit correspond au problème Maximum-Througput- Bounded-Degree (MTBD) qui a été analysé dans~\cite{beaumont08}. Il a été montré que le problème est NP-Complet au sens fort mais qu'une augmentation de ressources minimale (de 1) sur le degré maximal des serveurs permet de le résoudre en temps polynomial. Dans cet article, nous considérons une extension de MTBD à la situation plus réaliste, dans le contexte des plates-formes de calcul à grande échelle, dans laquelle les nœuds esclaves rejoignent et quittent dynamiquement la plate-forme à des instants arbitraires (problème online MTBD). Nous montrons tout d'abord qu'aucun algorithme complètement à la volée (c.-à.-d. qui n'autorise pas les déconnections) ne peut conduire à un facteur d'approximation constant, quelle que soit l'augmentation de ressources utilisée. Ensuite, nous montrons qu'il est en fait possible de maintenir à tout instant la solution optimale (avec une augmentation de ressource additive de 1) en ne réalisant à chaque modification de la plate-forme qu'une déconnection et qu'une nouvelle connection par maître.

Published
2009

44. Broadcasting on Large Scale Heterogeneous Platforms under the Bounded Multi-Port Model.

Author

Beaumont, Olivier, Bonichon, Nicolas, Eyraud-Dubois, Lionel, Uznanski, Przemyslaw, and Agrawal, Shailesh Kumar

Subjects
HETEROGENEOUS computing, DISTRIBUTED computing, COMPUTER scheduling, COMPUTER algorithms, COMPUTER simulation
Abstract

We consider the classical problem of broadcasting a large message at an optimal rate in a large scale distributed network under the multi-port communication model. In this context, we are interested in both building an overlay network and providing an explicit algorithm for scheduling the communications. From an optimization point of view, we aim both at maximizing the throughput (i.e., the rate at which nodes receive the message) and minimizing the degree of the participating nodes, i.e., the number of TCP connections they must handle simultaneously. The main novelties of our approach are the introduction of this degree constraint and the classification of the set of participating nodes into two parts: open nodes that stay in the open-Internet and “guarded” nodes that lie behind firewalls or NATs. Two guarded nodes cannot communicate directly, but rather need to use an open node as a gateway for transmitting a message. In the case without guarded nodes, we prove that it is possible to reach the optimal throughput, at the price of a quasi-optimal (up to a small additive increase) degree of the participating nodes. In presence of guarded nodes, our main contributions are a closed form formula for the optimal cyclic throughput and the proof that the optimal solution may require arbitrarily large degrees. In the acyclic case, we propose an algorithm that reaches the optimal throughput with low degree. Then, we prove a worst case ratio between the optimal acyclic and cyclic throughput and show through simulations that this ratio is on average very close to 1, what makes acyclic solutions efficient both in terms of throughput maximization and degree minimization. [ABSTRACT FROM AUTHOR]

Published
2014
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46. Postcombustion CO2 Capture by Chemical Absorption: Screening of Aqueous Amine(s)-based solvents.

Author

Dubois, Lionel and Thomas, Diane

Abstract

Abstract: The purpose of our work was to evaluate separately the absorption and regeneration performances of different types of amine(s) based solvents (primary, secondary and tertiary alkanolamines, sterically hindered amines, non-cyclical tetramine and cyclical absorption activators) by carrying out screening tests using small scale apparatus: a gas-liquid contactor for absorption, namely a double-stirred cell, and a regeneration cell. Absorption and regeneration performances of the solvents were compared thanks to calculated absorption and regeneration efficiencies. Concerning the absorption results, the positive effect of an activator, and especially the cyclical di-amine piperazine (PZ), on the absorption performances of the different simple amine solutions was clearly highlighted. The activation of the secondary amine MMEA by PZ gives also higher absorption efficiencies. Regarding the regeneration tests, the better regeneration performances of tertiary and sterically hindered amines (MDEA and AMP) were confirmed. For the amines blends, higher regeneration performances were observed with PZ activated solutions than with PIP activated solutions. These absorption and regeneration results will be taken into account in the solvent selection for future combined absorption-regeneration tests. [Copyright &y& Elsevier]

Published
2013
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47. Study of the Postcombustion CO2 Capture by Absorption into Amine(s) Based Solvents: Application to Cement Flue Gases.

Author

Dubois, Lionel and Thomas, Diane

Abstract

Abstract: The purpose of this work was to evaluate the absorption-regeneration performances of different types of amine(s) based solvents (primary, secondary and tertiary alkanolamines, sterically hindered amines, non-cyclical tetramine and cyclical absorption activators), previously selected thanks to a methodological study and separate laboratory absorption and regeneration tests. In this work absorption-regeneration experiments were carried out using a newly developed CO2 capture laboratory micro-pilot and applying a high gaseous CO2 content (from 20% to 30%) representative of cement plant flue gases. The different experiments allowed us to compare a large number of solvents (simples and blends) by weighing absorption and regeneration performances measured in our plant. The positive effect of an activator (especially the cyclical di-amine piperazine, from 5 to 10%) on the absorption-regeneration performances of the different solutions (especially on the sterically hindered amine 2-amino-2-methyl-1-propanol and on the secondary amines diethanolamine and methylmonoethanolamine, 30% solutions) was clearly highlighted. The influence of other components present in industrial emissions, especially in cement plant flue gases (mainly O2, SOx, and NOx), on the absorption-regeneration performances of the amine solvents was also studied. [Copyright &y& Elsevier]

Published
2013
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48. Heterogeneous Resource Allocation under Degree Constraints.

Author

Beaumont, Olivier, Eyraud-Dubois, Lionel, Thraves Caro, Christopher, and Rejeb, Hejer

Subjects
*RESOURCE allocation, *CLIENT/SERVER computing, *APPROXIMATION algorithms, *CLOUD computing, *BIN packing problem, *COMPUTER scheduling
Abstract

In this paper, we consider the problem of assigning a set of clients with demands to a set of servers with capacities and degree constraints. The goal is to find an allocation such that the number of clients assigned to a server is smaller than the server's degree and their overall demand is smaller than the server's capacity, while maximizing the overall throughput. This problem has several natural applications in the context of independent tasks scheduling or virtual machines allocation. We consider both the offline (when clients are known beforehand) and the online (when clients can join and leave the system at any time) versions of the problem. We first show that the degree constraint on the maximal number of clients that a server can handle is realistic in many contexts. Then, our main contribution is to prove that even if it makes the allocation problem more difficult (NP-Complete), a very small additive resource augmentation on the servers degree is enough to find in polynomial time a solution that achieves at least the optimal throughput. After a set of theoretical results on the complexity of the offline and online versions of the problem, we propose several other greedy heuristics to solve the online problem and we compare the performance (in terms of throughput) and the cost (in terms of disconnections and reconnections) of all proposed algorithms through a set of extensive simulation results. [ABSTRACT FROM AUTHOR]

Published
2013
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50. Mapping hydrophobic molecular regions using dissolved laser-polarized xenon NMR

Author

Dubois, Lionel, Berthault, Patrick, Huber, J. Gaspard, and Desvaux, Hervé

Subjects
*HYDROPHOBIC surfaces, *MAGNETIZATION, *PROTONS, *MOLECULAR rotation, *XENON
Abstract

Molecular hydrophobic cavities can be mapped thanks to the detection of magnetization transfer from laser polarized xenon to nearby protons. This so called SPINOE approach is described. The study of the spin dynamics during this experiment and its consequences on the practical implementation are detailed. We show that thanks to the knowledge of the physical properties of the system, it becomes possible to choose the best experimental conditions in order to be able to assign magnetization transfer through two dimensional NMR methods. As an illustration, the first 2D SPIROE-TOCSY experiment is reported. To cite this article: L. Dubois et al., C. R. Physique 5 (2004). [Copyright &y& Elsevier]

Published
2004
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