Combining Processor Virtualization and Split Compilation for Heterogeneous Multicore Embedded Systems

Complex embedded systems have always been heterogeneous multicore systems. Because of the tight constraints on power, performance and cost, this situation is not likely to change any time soon. As a result, the software environments required to program those systems have become very complex too. We propose to apply instruction set virtualization and just-in-time compilation techniques to program heterogeneous multicore embedded systems, with several additional requirements: * the environment must be able to compile legacy C/C++ code to a target independent intermediate representation; * the just-in-time (JIT) compiler must generate high performance code; * the technology must be able to program the whole system, not just the host processor. Advantages that derive from such an environment include, among others, much simpler software engineering, reduced maintenance costs, reduced legacy code problems... It also goes beyond mere binary compatibility by providing a better exploitation of the hardware platform. We also propose to combine processor virtualization with split compilation to improve the performance of the JIT compiler. Taking advantage of the two-step compilation process, we want to make it possible to run very aggressive optimizations online, even on a very constraint system

Humanités numériques et web sémantique : de l'intérêt de la modélisation des connaissances en histoire des sciences et des techniques pour une histoire comparée des ports de Brest (France) et Mar del Plata (Argentine)

International audienceLe projet présenté dans cette communication s'insère dans les programmes de recherche "Histoire des sciences et des technologies de la mer" & "Humanités numériques" développés au sein du Centre F. Viète (EA 1161). Il s'agit ici de discuter l'intérêt de s'appuyer sur le web sémantique et de développer des ontologies dans une approche pluridisciplinaire couplant SHS et STIC. Nous discuterons en conclusion les questions épistémologiques qui sont posées à l'historien face à ces nouvelles pratiques

Infrastructures and Compilation Strategies for the Performance of Computing Systems

This document presents our main contributions to the field of compilation, and more generally to the quest of performance ofcomputing systems.It is structured by type of execution environment, from static compilation (execution of native code), to JIT compilation, and purelydynamic optimization. We also consider interpreters. In each chapter, we give a focus on the most relevant contributions.Chapter 2 describes our work about static compilation. It covers a long time frame (from PhD work 1995--1998 to recent work on real-timesystems and worst-case execution times at Inria in 2015) and various positions, both in academia and in the industry.My research on JIT compilers started in the mid-2000s at STMicroelectronics, and is still ongoing. Chapter 3 covers the results we obtained on various aspects of JIT compilers: split-compilation, interaction with real-time systems, and obfuscation.Chapter 4 reports on dynamic binary optimization, a research effort started more recently, in 2012. This considers the optimization of a native binary (without source code), while it runs. It incurs significant challenges but also opportunities.Interpreters represent an alternative way to execute code. Instead of native code generation, an interpreter executes an infinite loop thatcontinuously reads a instruction, decodes it and executes its semantics. Interpreters are much easier to develop than compilers,they are also much more portable, often requiring a simple recompilation. The price to pay is the reduced performance. Chapter 5presents some of our work related to interpreters.All this research often required significant software infrastructures for validation, from early prototypes to robust quasi products, andfrom open-source to proprietary. We detail them in Chapter 6.The last chapter concludes and gives some perspectives

Infrastructures et stratégies de compilation pour parallélisme à grain fin

The increasing complexity of processors has led to the development of a large number of code transformations to adapt computations to the hardware architecture. The major difficulty faced by a compiler is to determine the sequence of transformations that will provide the best performance. This sequence depends on the application and the processor considered. The deep interaction between the various code transformations does not allow to find a static solution.We propose an iterative approach to compilation to solve this problem: each optimization module can revisit the decisions made by another module. These modules can communicate information about the properties of the code they have produced. This approach requires a complete redesign of the structure of current compilers.The realization was only made possible thanks to the software infrastructures that we developed: Salto and SEA. Thanks to these environments, we were able to quickly develop prototypes of compilation strategies.We also show that analysis and optimization should not be limited to the local behavior of a code fragment. On the contrary, the global behavior of the application must be considered, especially for embedded systems.La complexité croissante des processeurs a conduit au développement d'un grand nombre de transformations de code pour adapter l'organisation des calculs à l'architecture matérielle. La difficulté majeure à laquelle est confronté un compilateur consiste à déterminer la séquence de transformations qui va fournir la meilleure performance. Cette séquence dépend de l'application et du processeur considérés. L'interaction profonde entre les diverses transformations de code ne permet pas de trouver une solution statique.Nous proposons une approche itérative de la compilation pour résoudre ce problème : chaque module d'optimisation peut remettre en cause les décisions prises par un autre module. Ces modules peuvent se communiquer des informations sur les propriétés du code qu'ils ont produit. Cette approche nécessite une refonte complète de la structure des compilateurs actuels.La réalisation n'a été rendue possible que grâce aux infrastructures logicielles que nous avons développées : Salto et SEA. Grâce à ces environnements nous avons pu développer rapidement des prototypes de stratégies de compilation.Nous montrons aussi que l'analyse et l'optimisation ne doivent pas se contenter d'un comportement local à un fragment de code. Au contraire, le comportement global de l'application doit être considéré, en particulier pour les systèmes enfouis

Lie symmetries applied to guaranteed integration: application to mobile robotics localisation

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So Far So Good: Self-Adaptive Dynamic Checkpointing for Intermittent Computation based on Self-Modifying Code

International audienceRecently, different software and hardware based checkpointing strategies have been proposed to ensure forward progress toward execution for energy harvesting IoT devices. In this work, inspired by the idea used in dynamic compilers, we propose SFSG: a dynamic strategy, which shifts checkpoint placement and specialization to the runtime and takes decisions based on the past power failures and execution paths taken before each power failure. The goal of SFSG is to provide forward progress and to avoid facing non-termination without using hardware features or programmer intervention. We evaluate SFSG on a TI MSP430 device, with different types of benchmarks as well as different uninterrupted intervals, and we evaluate it in terms of the number of checkpoints and its runtime overhead

The Pitfalls of Benchmarking with Applications

International audienceApplication benchmarking is a widely trusted method of performance evaluation. Compiler developers rely on them to assess the correctness and performance of their optimizations; computer vendors use them to compare their respective machines; processor architects run them to tune innovative features, and — to a lesser extent — to validate their correctness. Benchmarks must reflect actual workloads of interest, and return a synthetic measure of “performance”. Often, benchmarks are simply a collection of real-world applications run as black boxes. We identify a number of pitfalls that derive from using applications as benchmarks, and we illustrate them with a popular, freely available, benchmark suite. In particular, we advocate the fact that correctness should be defined by an expert of the application domain, and the test should be integrated in the benchmark

Pancreatic head cancer in patients with chronic pancreatitis

International audienceBACKGROUND: Chronic pancreatitis (CP) is a risk factor of pancreatic adenocarcinoma (PA). The discovery of a pancreatic head lesion in CP frequently leads to a pancreaticoduodenectomy (PD) which preceded by a multidisciplinary meeting (MM). The aim of this study was to evaluate the relevance between this indication of PD and the definitive pathological results. METHODS: Between 2000 and 2010, all patients with CP who underwent PD for suspicion of PA without any histological proof were retrospectively analyzed. The operative decision has always been made at an MM. The definitive pathological finding was retrospectively confronted with the decision made at an MM, and patients were classified in two groups according to this concordance (group 1) or not (group 2). Clinical and biological parameters were analyzed, preoperative imaging were reread, and confronted to pathological findings in order to identify predictive factors of malignant degeneration. RESULTS: During the study period, five of 18 (group 1) patients with CP had PD were histologically confirmed to have PA, and the other 13 (group 2) did not have PA. The median age was 52.5+/-8.2 years (gender ratio 3.5). The main symptoms were pain (94.4%) and weight loss (72.2%). There was no patient's death. Six (33.3%) patients had a major complication (Clavien-Dindo classification ≥ 3). There was no statistical difference in clinical and biological parameters between the two groups. The rereading of imaging data could not detect efficiently all patients with PA. CONCLUSIONS: Our results confirmed the difficulty in detecting malignant transformation in patients with CP before surgery and therefore an elevated rate of unnecessary PD was found. A uniform imaging protocol is necessary to avoid PD as a less invasive treatment could be proposed

Vapor SIMD: Auto-Vectorize Once, Run Everywhere

International audienceJust-in-Time (JIT) compiler technology offers portability while facilitating target- and context-specific specialization. Single-Instruction-Multiple-Data (SIMD) hardware is ubiquitous and markedly diverse, but can be difficult for JIT compilers to efficiently target due to resource and budget constraints. We present our design for a synergistic auto-vectorizing compilation scheme. The scheme is composed of an aggressive, generic offline stage coupled with a lightweight, target-specific online stage. Our method leverages the optimized intermediate results provided by the first stage across disparate SIMD architectures from different vendors, having distinct characteristics ranging from different vector sizes, memory alignment and access constraints, to special computational idioms.We demonstrate the effectiveness of our design using a set of kernels that exercise innermost loop, outer loop, as well as straight-line code vectorization, all automatically extracted by the common offline compilation stage. This results in performance comparable to that provided by specialized monolithic offline compilers. Our framework is implemented using open-source tools and standards, thereby promoting interoperability and extendibility