Calculatrice

Résumé

thumb|Une pascaline. Inventée au , c'est la première machine à calculer. Une calculatrice ou calculette (terme souvent considéré comme péjoratif par les fabricants) est une machine conçue pour simplifier et fiabiliser des opérations de calcul. D'abord mécanique, puis électromécanique, la machine à calculer est devenue électronique dans les , avec l'introduction de la première machine à calculer électronique en 1961, suivie d'une miniaturisation accélérée des circuits intégrés. Les machines les plus simples se limitent aux quatre opérations arithmétiques usuelles, tandis que les calculatrices programmables les plus sophistiquées disposent d'une expressivité équivalente aux ordinateurs (voir Machine de Turing et Turing-complet). Calculatrices mécaniques Calculatrice mécanique Bien qu'il n'y ait pas, à proprement parler, de filiation technologique entre les calculatrices mécaniques et les calculatrices électroniques, il n'est pas inutile d'évoquer ici les outils utilisés pou

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https://fr.wikipedia.org/wiki/Calculatrice

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Un ordinateur est un système de traitement de l'information programmable tel que défini par Alan Turing et qui fonctionne par la lecture séquentielle d'un ensemble d'instructions, organisées en progr

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Une calculatrice programmable est une calculatrice capable d'être programmée, d'une façon similaire à un ordinateur. Elle diffère de la simple calculatrice par sa faculté d'exécuter des algorithmes

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Adding limited reconfigurability to superscalar processors

Marc Epalza

For the last thirty years, electronics, at first built with discrete components, and then as Integrated Circuits (IC), have brought diverse and lasting improvements to our quality of life. Examples might include digital calculators, automotive and airplane control assistance, almost all electrical household appliances, and the almost ubiquitous Personal Computer. Application-Specific Integrated Circuits (ASICs) were traditionally used for their high performance and low manufacturing cost, and were designed specifically for a single application with large volumes. But as lower product lifetimes and the pressures of fast marketing increased, ASICs' high design cost pushed for their replacement by Microprocessors. These processors, capable of implementing any functionality through a change in software, are thus often called General Purpose Processors. General purpose processors are used for everyday computing tasks, and found in all personal computers. They are also often used as building blocks for scientific supercomputers. Superscalar processors such as these require ever more processing power to run complex simulations, video games or versatile telecoms services. In the case of embedded applications, e.g. for portable devices, both performance and power consumption must be taken into account. In a bid to adapt a processor to some extent to select applications, fully reconfigurable logic can greatly improve the performance of a processor, since it is shaped for the best possible execution with the available resources. However, as reconfigurable logic is far slower than custom logic, this gain is possible only for some specific applications with large parallelism, after a detailed study of the algorithm. Even though this process can be automated, it still requires large computing resources, and cannot be performed at run time. To reduce the loss in speed compared to custom logic, it is possible to limit the reconfigurability to increase the breadth of applications where performance can be improved. However, as the application space increases, a careful analysis and design of the reconfigurability is required to minimize the speed loss, notably when dynamic reconfiguration is considered. As a case study, we analyze the feasibility of adding limited reconfigurability to the Floating Point Units (FPUs) of a general purpose processor. These rather large units execute all floating point operations, and may also be used for integer multiplication. If an application contains few or infrequent instructions that must be executed by the FPU, this idle hardware only increases power consumption without enhancing performance. This is often the case in non-scientific applications and even many recent and detailed video games which make heavy use of hardware display accelerators for 3D graphics. In a fast multiplier such as can be found in the FPU of a high performance processor, the logic to perform multiplication is a large tree of compressors to add all the partial products together. It is possible to add logic to allow the reconfiguration of part of this tree as several extra Arithmetic and Logic Units (ALU). This requires a detailed timing analysis for both the reconfigurable FPU and the extra ALUs, taking into account effects such as added wires and longer critical paths. Finally, the algorithm to decide when and how to reconfigure must be studied, in terms of eciency and complexity. The results of adding this limited reconfigurability to a mainstream superscalar processor over a large set of compute intensive benchmarks show gains of up to 56% in the best case, with an average gain of 11%. The application to an idealized huge top processor still shows slightly positive average gains, as the limits of available parallelism are reached, bounded by both the application and many of the characteristics of the processor. In all cases, binary compatibility is maintained, allowing the re-use of all existing software. We show that adding limited reconfigurability to a general purpose superscalar processor can produce interesting gains over a wide range of applications while maintaining binary compatibility, and without large modifications to the original design. Limited reconfigurability is worthwhile as it increases the design space, allowing gains to apply to a larger set of applications. These gains are achieved through careful study and optimization of the reconfigurable logic and the decision algorithm.

EPFL2004

Chargement

In recent years, funding agencies, governments, and international organization have issued a series of research data management and sharing policies, like the H2020 [1]. Researchers are encouraged or required to share their production in an open way, including attached publications and data [2]. One consequence of those policies for researchers is the necessity of providing a DMP (Data Management Plan) when applying for funding. This DMP describes the life-cycle of the data during the funded project. In particular, researchers have to specify a description of the generated data, along with their storage, protection, publication and archive strategies. In order to assist researchers with those new requirements and provide them with good practices, many university libraries have developed services around the management of their data [3a][3b]. Among the many information required in a DMP, some are dedicated to the costs the researchers will face for their data management, storage or curation. Those questions are usually painful, as the applicant has to have full knowledge of existing providers for storage, archive or publication services. These providers can be part of their institution or exist outside. Few helpful information exists. One can find costing tools in form of a spreadsheet or a static document in which the researcher is lost or will spend a lot of time to find the needed information. Most of these tools do neither give any providers’ nor real cost information. It's in this context that the Research Data Management Team of EPFL Library has developed an online tool, creating a central place for researchers to find and calculate their costs related to the data life-cycle [4]. The tool contains a cost database that includes most of our institution services and some external providers. Furthermore, this tool provides good practice for the researchers around calculating costs. It is designed entirely for self-use and doesn't need any training. By using a modern code repository and open source libraries, the cost database can be updated and changed easily without specific technical knowledge, which makes deployment in other institutions handy. The cost database can be implemented with any kind of providers, such as institutional or private ones and adapted for any kind of pricing model. During the presentation, we will first introduce the tool and its functionalities, discuss the advantages for the researchers, and end with how the tool can be used by other interested partners. Bibliography [1] : Guedj, D., Ramjoué, C.: European Commission Policy on Open-Access to Scientific Publications and Research Data in Horizon 2020. Biomed Data J. 2015;1(1):11-14. DOI: http://dx.doi.org/10.11610/bmdj.01102 [2] : Whyte, A., Pryor, G.: Open Science in Practice: Researcher Perspectives and Participation. Int. J. Digit. Curation. 6, 199–213 (2011). DOI : https://doi.org/10.2218/ijdc.v6i1.182 [3a] : Peters, C., Dryden, A.R.: Assessing the Academic Library’s Role in Campus-Wide Research Data Management: A First Step at the University of Houston. Sci. Technol. Libr. 30, 387–403 (2011). DOI : https://doi.org/10.1080/0194262X.2011.626340 [3b] : Tenopir, C. et al.: Research Data Services in European Academic Research Libraries, LIBER Quarterly, vol. 27, n° 1, 23‑44 (2017). DOI : http://doi.org/10.18352/lq.10180 [4] : Cost Calculator, A. Masson, EPFL Library DOI: http://dx.doi.org/10.5281/zenodo.1469035 https://rdmepfl.github.io/costcalc/

2019

Chargement

Scenario modelling and optimisation of renewable energy integration for the energy transition

Victor Codina Gironès

A large number of countries have engaged themselves in an energy transition towards more re- newable energy in their energy systems. Motivations stem mainly from the need to reduce CO2 emissions, and from a desire of their population to phase out technologies such as nuclear. Most of these countries promote biomass, wind and solar energy sources, among other possibilities. How- ever the current rate of deployment of renewable energy systems globally is not sufficient to reach the CO2 emissions reduction that would allow to maintain the global average temperature increase below the 2°C threshold. The main barriers to a wider integration of renewable energy systems are i) their limited realisable potential, ii) their still limited competitiveness, iii) their intermittence; iv) public acceptance often related to poor level of energy literacy amongst citizens. Citizens are key decision-makers. They must decide on energy policies and on the energy technologies they use, hence they have the power to foster or halt the energy transition. This thesis presents two different strategies for addressing the problem of the integration of re- newable energy sources for energy transitions. The first one (Chapter 1) consists in developing an energy modelling tool to help decision-makers understand the energy system and find their own answers. The modelling approach also includes a new methodology for the calculation of the total cost of a national energy system. A model of the Swiss energy system has been created following this approach, which serves as basis to develop the Swiss-Energyscope online calculator. This calculator and its model present an optimal trade-off between scientific rigour and user-friendliness, which allows the reproduction of the energy transition scenarios conceived by the Swiss Government, and consequently its use for energy policy making. The second strategy (chapters 2 and 3) profits from the possibilities offered by mathematical mod- elling and optimisation to analyse national energy systems, and derive insights for policy and decision-makers. First, a methodology using a mix-integer linear programming (MILP) model analyses biomass usage pathways to determine its optimal use in Switzeland in 2035. Second, in order to study the role of biomass, non-linear optimisation is applied to create future scenarios. (Chapter 3) focuses on the solutions to deal with the variability of renewable electricity. To this end, a MILP model with hourly time resolution is conceived to study the use of flexible electricity supply and demand options for the integration of renewable electricity. The optimisation methodologies are validated on case studies for the Swiss energy system. Regarding biomass, the results reveal that woody biomass chemical conversion technologies can allow for an overall better performance in terms of CO2 avoided emissions compared to direct combustion, as long as the produced biofuels are used in efficient technologies. Results also show that the combination of the gasification-methanation process of woody biomass with the production of H2 produced from excess electricity would allow to reduce the Swiss natural gas imports to zero by 2050. Concerning the integration of variable renewable electricity, the cost difference between using flexible electricity supply- and demand-options or electricity imports to deal with variable renewable electricity is below 2.5% of the total cost of the energy system.

EPFL2018

Chargement

Adding limited reconfigurability to superscalar processors

Marc Epalza

EPFL2004

Scenario modelling and optimisation of renewable energy integration for the energy transition

Victor Codina Gironès

EPFL2018

2019