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Concept

Algorithme de recherche

En informatique, un algorithme de recherche est un type d'algorithme qui, pour un domaine, un problème de ce domaine et des critères donnés, retourne en résultat un ensemble de solutions répondant au problème. Supposons que l'ensemble de ses entrées soit divisible en sous-ensemble, par rapport à un critère donné, qui peut être, par exemple, une relation d'ordre. De façon générale, un tel algorithme vérifie un certain nombre de ces entrées et retourne en sortie une ou plusieurs des entrées visées. L'ensemble de toutes les solutions potentielles dans le domaine est appelé espace de recherche. Algorithmes de recherche classique Sur des structures de données usuelles comme les listes, les tables ou les arbres, il existe des algorithmes bien connus que l'on peut facilement mettre en œuvre et qui exploitent les propriétés de la structure de données . Un exemple classique est la recherche dichotomique où l'on divise en deux l'espace de recherche à chaque tentative ce qui don

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Scaling Functional Synthesis and Repair

Emmanouil Koukoutos

Program synthesis was first proposed a few decades ago, but in the last decade it has gained increased momentum in the research community. The increasing complexity of software has dictated the urgent need for improved supporting tools that verify the software's correctness, and that automatically generate code from a formal contract provided by the programmer, along with a proof of the generated code's correctness. In addition, recent technological developments have provided tools that have enabled researchers to revisit the synthesis problem. The recent rise of SMT solvers has given synthesis tools a reliable and automated way to verify synthesized programs against contracts. The introduction of counter-example guided inductive synthesis has provided researchers with a flexible synthesis algorithm that they can adapt according to their specific domain. In this dissertation, we develop new algorithms to synthesize recursive functional programs with algebraic data types from formal specifications and/or input-output examples. We manage to scale beyond the reach of other similar tools to synthesize nontrivial functional programs, with a focus on data structure transformations. First, we address the problem of precisely specifying the desired space of candidate programs, described by context free grammars (CFGs). We implement and evaluate a method for reducing the program space by describing axioms of the target language and other domain-specific restrictions on the level of the CFG, without explicitly generating and rejecting undesirable programs. We provide a method that extracts a program model from a corpus of code and that builds a probabilistic CFG from it. We showcase the usefulness, both individually and in tandem, of these methods. Second, we develop an algorithm to efficiently traverse a possibly unbounded space of candidate programs generated from a probabilistic CFG. This algorithm is an implementation of the A* best-first search algorithm on the derivation graph generated from the CFG, with a number of domain-specific optimizations. We evaluate the efficiency of the algorithm as well as the effectiveness of the optimizations. Finally, we describe a program repair framework that locates and fixes bugs in erroneous functional programs. Our novel fault localization technique detects erroneous snippets with concrete execution and eliminates false positives by analyzing dependencies between execution traces. After the erroneous code snippet is discovered, a modified version of our synthesis algorithm generates fixes for it by introducing modifications to the original erroneous code.

EPFL2019

Chargement

Problèmes de cheminements optimaux dans les réseaux avec contraintes associées aux arcs

In this thesis we consider two optimal routing problems in networks. Both are NP-hard and are often used to modelize real life problems of large size. We first present the capacitated arc routing problem (CARP). In this problem, we have to serve a set of customers represented by the arcs of a network with vehicles of restricted capacity. The aim is to design a set of vehicle routes of least total cost. We describe two heuristic methods for the CARP based on local search techniques. The first one is a Tabu Search heuristic using an original post-optimization procedure. Principles appearing in this procedure are used to define a class of neighborhoods we combine in a Variable Neighborhood Descent method. Our algorithms compare favorably with some of her methods. They were initially developed to deal with the undirected CARP. We describe how to transform them so that they can be applied to the directed CARP. We also propose an adaptation to the directed case of a lower bound originally developed for the undirected CARP. This lower bound is used to evaluate the quality of the solutions produced by our algorithms for the directed CARP. Our methods obtain solutions whose value is, on average, close to known lower bounds. We use the CARP to tackle a real life problem of boat routing and scheduling. This problem can be viewed as a directed CARP with time windows. We describe in detail its modeling process and we analyze our first results. We obtain solutions that require less boats than the present schedule. Nevertheless, these solutions are not completely feasible in practice. We suggest some ways to improve them. The second problem treated in this thesis is the shortest capacitated paths problem (SCPP). We present a Tabu Search heuristic and some post-optimization procedures for the SCPP. These procedures are called in our Tabu Search algorithm. Two versions of this algorithm are considered. In the first one, post-optimization procedures are intensively used. In the second one, they are less frequently applied. This second version is faster. Compared with a greedy approach, the two versions of our Tabu Search heuristic obtain solutions which are, on average, of better quality. The SCPP was proposed to us by EDF (Electricité de France) in order to minimize the total length of the paths followed by cables in a nuclear power-station. It can also be viewed as a subproblem of the bandwidth packing problem (BWP) appearing in telecommunications.

EPFL2000

Chargement

Benchmark for Bimanual Robotic Manipulation of Semi-deformable Objects

Aude Billard, Fanjun Bu, Konstantinos Chatzilygeroudis, Bernardo Fichera, Farshad Khadivar, Ilaria Lauzana, Kunpeng Yao

We propose a new benchmarking protocol to evaluate algorithms for bimanual robotic manipulation semi-deformable objects. The benchmark is inspired from two real-world applications: (a) watchmaking craftsmanship, and (b) belt assembly in automobile engines. We provide two setups that try to highlight the following challenges: (a) manipulating objects via a tool, (b) placing irregularly shaped objects in the correct groove, (c) handling semi-deformable objects, and (d) bimanual coordination. We provide CAD drawings of the task pieces that can be easily 3D printed to ensure ease of reproduction,and detailed description of tasks and protocol for successful reproduction, as well as meaningful metrics for comparison. We propose four categories of submission in an attempt to make the benchmark accessible to a wide range of related fields spanning from adaptive control, motion planning to learning the tasks through trial-and-error learning.

2020

Chargement

Intelligence artificielle

vignette|redresse=0.8|Les assistants personnels intelligents sont l'une des applications concrètes de l'intelligence artificielle dans les années 2010. L'intelligence artificielle (IA) est un ensembl

Algorithme

thumb|Algorithme de découpe d'un polygone quelconque en triangles (triangulation). Un algorithme est une suite finie et non ambiguë d'instructions et d’opérations permettant de résoudre une classe de

Apprentissage automatique

L'apprentissage automatique (en anglais : machine learning, « apprentissage machine »), apprentissage artificiel ou apprentissage statistique est

CS-119(c): Information, Computation, Communication

L'objectif de ce cours est d'introduire les étudiants à la pensée algorithmique, de les familiariser avec les fondamentaux de l'Informatique et de développer une première compétence en programmation (langage C++).

CS-101: Advanced information, computation, communication I

Discrete mathematics is a discipline with applications to almost all areas of study. It provides a set of indispensable tools to computer science in particular. This course reviews (familiar) topics as diverse as mathematical reasoning, combinatorics, discrete structures & algorithmic thinking.

CS-308: Quantum computation

The course introduces teh paradigm of quantum computation in an axiomatic way. We introduce the notion of quantum bit, gates, circuits and we treat the most important quantum algorithms. We also touch upon error correcting codes. This course is independent of COM-309.