When you want to design and simulate a real issue (be a question of population dynamism in ecology, tumor growth in biomedical engineering, combustion dynamics in new-generation rocket engines - for example at SpaceX, prediction of solar storms and magnetic reconnection phenomena in solar physics, simulation of turbulence and turbulent combustion in fluid mechanics) the engineer or the researcher in applied mathematics or in "computational science" has to use a range of digital methods and must be able to analyze it mathematically, assess in terms of quality and computational efficacity, and finally, implement.

 

This course offers an introduction to numerical analysis, starting with the mathematical foundations on which numerical methods are based through to the implementation and the use of these methods on Jupyter notebooks (an active field at the Ecole Polytechnique), including their stability in relation to mathematical conditioning of the problems posed. The link is made with applications to understand the extent to which this type of method can be used from a practical point of view. Implementations of these methods in existing digital libraries are also documented.

 

Every class sessions include an analysis of the mathematical foundations on which a numerical method class is built, a description and analysis of the digital method (with a historical perspective). Those two aspects are covered during the course. The PC offers a review and an in-depth look at some concepts of the course, use of the method in the context of Jupyter notebooks and a description of how students can implement the method in a notebook to be handed in for the next class session.

This course has three objectives:

The first one is to introduce mathematical statistics tools and statistical learning ("machine learning"). We will describe everything from the choice of a statistical model, to parameter estimation, inference and model selection. We will learn how to build estimators, tests and classification rules, and how to evaluate the performance of these rules. We will introduce a number of theoretical tools - decision theory, empirical process.

The second objective is to describe, in the course and in small classes, concrete examples of modeling in various fields (signal and image processing, econometrics, environmental sciences, shape classification, etc.).

The third objective is to develop a well-founded practical savoir-faire enabling students to understand how theoretical tools can be implemented in concrete applications (use of R or Python).

The last two courses will be devoted to an introduction to statistical learning.

Evaluation: Written exam, two take-home assignments, two quizzes.

The objective of this "Modal" is to learn how to develop an experimental approach to a for a wide range of numerical methods in Applied Mathematics for industrial or research purposes.

This complements the theoretical content of the 2nd year courses.

We will typically ask ourselves these kinds of questions:

- how to illustrate this theoretical result of convergence?
- what are the critical parameters for this optimization problem?
- what happens for n "small" in this theorem?
- why is this algorithm unusable in practice?

 

Partial differential equations play a fundamental role in modeling complex phenomenon in fields as varied as mechanics, physics, and biology. Since the 1950s and the advent of computers, the development and use of numerical methods for the approximate machine calculation of solutions to partial differential equations have become routine in engineering. In automotive engineering, for example, not only deformations of the passenger compartment in the event of an impact but also air conditioning, ambient noise and electromagnetic compatibility are nowadays calculated by computer.

The course aims to highlight the link between classical mechanical and physical models based on partial differential equations, the underlying mathematical analysis, and the development of the finite element method. The common thread will be the variational point of view, which enables problems to be rewritten as minimization problems, making the link with optimization. A significant part of the course will be devoted to machine implementation of the finite element method and to the explicit approximate solution of certain partial differential equations using FreeFem++ software. In particular, students will be asked to carry out a mini-project using this software.

In addition, some of the PCs will illustrate on computer the concepts seen in class.

Evaluation: A written exam, quiz and mandatory mini-project.

Randomness plays a decisive role in a variety of contexts, and it is often necessary to take it into account in many aspects of the engineering sciences, we can name telecommunications, pattern recognition or network administration.

More generally, randomness is also a factor in economics (risk management), medicine (epidemic propagation), biology (population evolution) and statistical physics (phase transition theory).

In applications, data observed over time are often modeled by correlated random variables whose behavior we would like to predict. The aim of this course is to formalize these notions by studying two types of random processes that are fundamental to probability theory: Markov chains and martingales. Various applications will be presented to illustrate these concepts.


Bibliographical reference


"Promenade aléatoire: chaînes de Markhov et martingales", Thierry Bodineau (2023)

Level required: Good knowledge of core course MAP361.

Evaluation methods : A grading test at the end of the course.

 

Introduction to Applied Mathematics through an experimental approach

This course is an introduction to the optimization and control of dynamical systems which are necessary tools in the design and management of systems that stem from sciences, technology, industry or services.

The first part of the course will be on optimization, with or without constraints, in finite or infinite dimensions. After introducing some theoretical results on optimality conditions, the main focus will be on gradient-type numerical algorithms. Special attention will be paid to some important classes of problems, such as linear programming or sequential quadratic programming.

For the second part of the course, we will study the control of differential equations modeling time evolution problems. The notions of controllability, adjoint state and the minimum principle of Pontryaguine will be introduced.

Beyond these technical aspects, this course is also intended to illustrate the typical approach of applied mathematics which mixes modelization, mathematical analysis and numerical simulation, which are necessary to master in any innovative processes.

The aim of this project is to propose methods for solving the resulting optimization issues, implement these methods and test them.

Topic 1(Frédéric Meunier): the organization of the production line in "Bucket Brigades" ensures great flexibility, while often having a production rate that is close to optimal. For order-picking lines, this type of organization presents a number of difficulties, and Pyung-Hoi Koo (Operations Research Spectrum, 2009) proposed ways to offset them while leaving several aspects open to further optimization.

 

Topic 2 (Frédéric Meunier): it is considered a workshop production issue, in which employees have a variety of qualifications. Products arrive according to a Poisson process, and each must visit a subset of the machines in a specific order. The arrival rate being quite high, queues can be formed in front of machines. As the employees are less numerous than the machines, the challenge is to pick which machine will be sent to an employee who has just completed a task. The aim of the project is to find the assignment rules that will keep the average stay time as low as possible.

 

Topic 3 (Eric Gourdin): We're interested in routing in Internet networks, which we'll first simulate and then optimize. The network is modeled by a graph whose links (edges/arcs) are equipped with capacities. We also have a set of requests, each request is defined by a source node, a destination node, and a volume of traffic to be handled. It is assumed that the network uses a shortest-path routing protocol: each link is assigned a (presumably given) administrative metric value, and traffic between the source and destination nodes is routed along the shortest paths (as defined by these administrative metrics). If there is more than one shortest path, traffic is distributed over the paths in accordance with the ECMP protocol. Link load is the ratio of traffic flow and capacity. Routing "quality" is measured by calculating the load of the fullest link. We'll take an interest in routing protocol evolution called  "Segment Routing" where a request can be routed on a continuation of segments, the routing within each segment being by itself managed by the shortest paths.

 

Topic 4 (Eric Gourdin): in an Internet network, we're seeking to calculate a "robust" routing called "oblivious routing". The general context is similar to the previous topic: a graph with links provided with capacities, a set of requests to be handled. Unlike the previous topic, the routing to be calculated is totally free (traffic can be split over as many paths as you like, as long as you satisfy the flow conservation on each intermediate vertex). It is assumed that request volumes are unknown. We are looking for a routing that is valid for all possible requests and such the maximum overall request sets of the ratio between the max load with this single routing and the ratio obtained with a routing that would be optimized for this request set be as small as possible (oblivious routing). The modal approach consists in offering ways of calculating (or approximating) this "oblivious" routing.

 

This MODAL is about  Monte Carlo methods for rare event simulations.

It starts with a refresh on usual Monte carlo methods, and on theoretical tools for the study of their efficiency. Then, essentially three methods will be introduced for rare event simulation:  importance sampling, splitting methods and adaptive multilevel methods. There will be an emphazis on the so-called Poisson case, and Gaussian case.