Ludovic Courtès

Ludovic Courtès

As software has become an integral part of scientific workflows, reproducible research practices must take it into account. In what way? Archiving source code is a necessary but insufficient condition. The ability to redeploy software environments, which at first sight may be viewed as a technical detail, is in fact a requirement. This article explores tools and methods to achieve this goal.

Ludovic Courtès

GNU Guix is a " functional " package manager that builds upon earlier work on Nix. Guix implements high-level abstractions such as packages and operating system services as domain-specic languages (DSLs) embedded in Scheme. It also implements build actions and operating system orchestration in Scheme. This leads to a multi-tier programming environment where embedded code snippets are staged for eventual execution. This paper presents G-expressions or " gexps ", the staging mechanism we devised for Guix. We explain our journey from traditional Lisp S-expressions to G-expressions, which augment the former with contextual information and ensure hygienic code staging. We discuss the implementation of gexps and report on our experience using them in a variety of operating system use cases-from package build processes to system services. Gexps provide a novel way to cover many aspects of OS connguration in a single, multi-tier language, while facilitating code reuse and code sharing .

Ludovic Courtès, Ricardo Wurmus

Support teams of high-performance computing (HPC) systems often find themselves between a rock and a hard place: on one hand, they understandably administrate these large systems in a conservative way, but on the other hand, they try to satisfy their users by deploying up-to-date tool chains as well as libraries and scientific software. HPC system users often have no guarantee that they will be able to reproduce results at a later point in time, even on the same system-software may have been upgraded, removed, or recompiled under their feet, and they have little hope of being able to reproduce the same software environment elsewhere. We present GNU Guix and the functional package management paradigm and show how it can improve reproducibility and sharing among researchers with representative use cases.

Ludovic Courtès

The INDES project-team of Inria has been developing HOP, a multi-tier language for Web programming. As part of the RAPP FP7 European project, the team has set out to use HOP as the lingua franca of the robotics applications developed within that project. Part of the challenge lies in the integration of existing robotics code, written using ROS or custom libraries, with HOP-based application. This document reports on the implementation of rowe, a communication library designed the fill the gap between low-level robotics C components on one hand, and other C, C++, ROS, or HOP components on the other. The library aims to be a lightweight, high-performance, "Web-friendly" communication library. It implements a socket-like interface that allows programs to exchange JSON objects over WebSockets. We describe the rationale, design, and implementation of rowe.