PhD Seminars: Developement of an Adjoint Model of Algorithmic Differentiation and Communication Techniques

Location: Salle Euler Violet
Chapter: Applied Mathematics and Simulations
Chairman: Konstantinos Mavreas (APICS)

Talk 1:       Scientific
Speaker:    Elaa Teftef - ECUADOR TEAM (Inria)
Title:          On two developments of the adjoint model of Algorithmic Differentiation to meet the needs of computationally intensive applications
Abstract:
This work is part of an European project, called ``AboutFlow'', which focuses on methods of optimization that are gradient-based. The adjoint mode of Algorithmic Differentiation (AD) is particularly attractive for computing gradients. However, this mode needs to use the intermediate values of the original simulation in reverse order at a cost that increases with the length of the simulation. AD research looks for strategies to reduce this cost, for instance by taking advantage of the structure of the given program. In this work, we consider on one hand the frequent case of Fixed-point loops for which several authors have proposed adapted adjoint strategies. Among these strategies, we select the one we find the best suited to be implemented in our AD tool. We specify further the selected method and we describe the way we implemented it in our AD tool. Experiments on a medium-size application shows a major reduction of the memory needed to store trajectories. On the other hand, we study checkpointing in the case of MPI parallel programs with point-to-point communications. We propose techniques to apply checkpointing to these programs. We provide proof of correctness of our techniques and we experiment them on representative CFD codes.

Talk 2:       General Interest
Speaker:    Nathalie Gayraud - ATHENA Team (Inria)
Title:          Communication and Scientific Dissemination Techniques
Abstract:
Which is the best way to communicate a scientific idea, so that it is crystal clear? How do we participate in a debate concerning our work, whithout confusing our audience? This talk, which will be for the most part interactive, aims to draw your attention onto some interesting debate and communication techniques.