Signal Rate Inference for Multi-Dimensional Faust

International audienceWe introduce a new signal-level, type-and rate-based semantic framework for describing a multi-rate version of the functional , domain-specific Faust language, dedicated to audio signal processing, and here extended to support array-valued samples. If Faust is usually viewed as a formalism for combining signal processors, which are expressions mapping input signals to output signals, we provide here the first formal, lower-level semantics for Faust based on signals instead. In addition to its interest in understanding the inner workings of the Faust compiler, which uses symbolic evaluation of signal expressions, this approach turns out to be useful when introducing a language extension targeting multi-rate and multi-dimensional (array-valued) processing. More precisely, we provide (1) new syntax and dynamic semantics for (recursive) Faust-based signals, (2) a type and, more interestingly, rational rate static semantics and (3) a new rate inference algorithm, together with its soundness and (relative) completeness theorems. Preliminary experiments in a prototype implementation of this extension in the Faust compiler are underway

Modeling the Temperature Bias of Power Consumption for Nanometer-Scale CPUs in Application Processors

We introduce and experimentally validate a new macro-level model of the CPU temperature/power relationship within nanometer-scale application processors or system-on-chips. By adopting a holistic view, this model is able to take into account many of the physical effects that occur within such systems. Together with two algorithms described in the paper, our results can be used, for instance by engineers designing power or thermal management units, to cancel the temperature-induced bias on power measurements. This will help them gather temperature-neutral power data while running multiple instance of their benchmarks. Also power requirements and system failure rates can be decreased by controlling the CPU's thermal behavior. Even though it is usually assumed that the temperature/power relationship is exponentially related, there is however a lack of publicly available physical temperature/power measurements to back up this assumption, something our paper corrects. Via measurements on two pertinent platforms sporting nanometer-scale application processors, we show that the power/temperature relationship is indeed very likely exponential over a 20{\deg}C to 85{\deg}C temperature range. Our data suggest that, for application processors operating between 20{\deg}C and 50{\deg}C, a quadratic model is still accurate and a linear approximation is acceptable.Comment: Submitted to SAMOS 2014; International Conference on Embedded Computer Systems: Architectures, Modeling, and Simulation (SAMOS XIV

Adventures in the (not so) Complex Space

International audienceWe report on the progress of a constructive mechanization for a small subset of signal processing theory, built upon the SSREFLECT and MATHCOMP libraries.The development was started to provide mechanized semantics for audio programming languages. Currently, we have formalized several standard properties of the Discrete Fourier Transform, such as its unitary matrix form and its power and convolution theorems. Future goals include transfer functions and constant overlap-add processing.At the workshop, we aim to discuss the needs and limits of our current approach, surveying some mathematical concepts not covered by existing libraries, and similar efforts in other frameworks and theorem provers

Liquid Clocks - Refinement Types for Time-Dependent Stream Functions

The concept of liquid clocks introduced in this paper is a significant step towards a more precise compile-time framework for the analysis of synchronous and polychromous languages. Compiling languages such as Lustre or SIGNAL indeed involves a number of static analyses of programs before they can be synthesized into executable code, e.g., synchronicity class characterization, clock assignment, static scheduling or causality analysis. These analyses are often equivalent to undecidable problems, necessitating abstracting such programs to provide sound yet incomplete analyses. Such abstractions unfortunately often lead to the rejection of programs that could very well be synthesized into deterministic code, provided abstraction refinement steps could be applied for more accurate analysis. To reduce the false negatives occurring during the compilation process, we leverage recent advances in type theory -- with the definition of decidable classes of value-dependent type systems -- and formal verification, linked to the development of efficient SAT/SMT solvers, to provide a type-theoretic approach that considers all the above analyses as type inference problems. In order to simplify the exposition of our new approach in this paper, we define a refinement type system for a minimalistic, synchronous, stream-processing language to concisely represent, analyse, and verify logical and quantitative properties of programs expressed as stream-processing data-flow networks. Our type system provides a new framework to represent logical time (clocks) and scheduling properties, and to describe their relations with stream values and, possibly, other quantas. We show how to analyze synchronous stream processing programs (à la Lustre, Signal) to enable previously described analyzes involved in compiling such programs. We also prove the soundness of our type system and elaborate on the adaptability of this core framework by outlining its extensibility to specific models of computations and other quantas

Parallelizing with BDSC, a resource-constrained scheduling algorithm for shared and distributed memory systems

International audienceWe introduce a new parallelization framework for scientific computing based on BDSC, an efficient automatic scheduling algorithm for parallel programs in the presence of resource constraints on the number of processors and their local memory size. BDSC extends Yang and Gerasoulis's Dominant Sequence Clus-tering (DSC) algorithm; it uses sophisticated cost models and addresses both shared and distributed parallel memory architectures. We describe BDSC, its integration within the PIPS compiler infrastructure and its application to the parallelization of four well-known scientific applications: Harris, ABF, equake and IS. Our experiments suggest that BDSC's focus on efficient resource man-agement leads to significant parallelization speedups on both shared and dis-tributed memory systems, improving upon DSC results, as shown by the com-parison of the sequential and parallelized versions of these four applications running on both OpenMP and MPI frameworks

Aligning Legivoc Legal Vocabularies by Crowdsourcing

International audiencelegivoc is the first Internet-based platform dedicated to the diffusion, edition and alignment of legal vocabularies across countries. Funded in part by the European Commission and administered by the French Ministry of Justice, legivoc offers a seamless path for governments to disseminate their legal foundations and specify semantic bridges between them. We describe the general principles behind the legivoc framework and provide some ideas about its implementation , with a particular focus on the state-of-the-art tools it includes to help crowdsource the alignment of legal corpora together. 1 Introduction legivoc 1 (all in lower case) is an Internet-based database platform dedicated to the management of multiple legal information terminologies, with a particular focus on vocabularies and their alignments [4]. The system is designed to be used both interactively and also as an automated Web service, interoperable with other document management tools or international legislation or translation systems, via a dedicated Application Programing Interface (API). The main goals of legivoc are: (1) to provide access, within a unique framework and using a general formalism, to (ultimately) all the legal vocabularies of the Member States of the European Union; (2) to foster the use of best practices regarding the encoding of these vocabularies using Internet standards such as the Simple Knowledge Organization System (SKOS) and Uniform Resource Identifier (URI); (3) to encourage the creation of alignment information between these vocabularies, helping provide bridges between judicial systems based on different laws and languages. The French Ministry of Justice spearheads the project, partly funded by the Euro-pean Commission and the Ministries of Justice of the Czech Republic, Spain, Finland, France, Italy and Luxembourg. ARMINES and MINES ParisTech are the lead scientific advisors and implementation specialists for the legivoc project. 1 http://legivoc.org (the site is open, although in an " alpha " version)

In and Out of SSA : a Denotational Specification

International audienceWe present non-standard denotational specifications of the SSA form and of its conversion processes from and to imperative programming languages. Thus, we provide a strong mathematical foundation for this intermediate code representation language used in modern compilers such as GCC or Intel CC. More specifically, we provide (1) a new functional approach to SSA, the Static Single Assignment form, together with its denotational semantics, (2) a collecting denotational semantics for a simple imperative language Imp, (3) a non-standard denotational semantics specifying the conversion of Imp to SSA and (4) a non-standard denotational semantics for the reverse SSA to Imp conversion process. These translations are proven correct, ensuring that the structure of the memory states manipulated by imperative constructs is preserved in compilers' middle ends that use the SSA form as control-flow data representation. Interestingly, a s unexpected by-products of our conversion procedures, we offer (1) a new proof of the reducibility of the RAM computing model to the domain of Kleene's partial recursive functions, to which SSA is strongly related, and, on a more practical note, (2) a new algorithm to perform program slicing in imperative programming languages. All these specifications have been prototyped using GNU Common Lisp. These fundamental results prove that the widely used SSA technology is sound. Our formal denotational framework further suggests that the SSA form could become a target of choice for other optimization analysis techniques such as abstract interpretation or partial evaluation. Indeed, since the SSA form is language-independent, the resulting optimizations would be automatically enabled for any source language supported by compilers such as GCC

Legivoc - connecting law in a changing world

International audienceOn the Internet, legal information is a sum of national laws. Even in a changing world, law is culturally specific (nation -specific most of the time) and legal concepts only become meaningful when put in the context of a particular legal system. Legivoc aims to be a semantic interface between the subject of law of a State and the other spaces of legal information that it will be led to use. This project will consist of setting up a server of multilingual legal vocabularies from the European Union Member States legal systems, which will be freely available, for other uses via an application programming interface (API).Sur l'internet, l'information juridique disponible est essentiellement une somme de droits nationaux. Même dans un monde en mouvement, même en acceptant une approche globalisée, le droit est d'abord une affaire de cultures (de cultures nationales le plus souvent) et les concepts juridiques n'ont de sens qu'accompagné de l'environnement juridique auquel ils sont rattachés. Face à ce constat, Legivoc vise à être une interface sémantique entre le sujet de droit d'un État et les différents espaces d'informations juridiques qu'il sera amené à utiliser. Ce projet consistera d'abord à mettre en place un serveur de vocabulaires juridique multilingue de chacun des États membres de l'Union européenne