A scalable approach for Variational Data Assimilation

Data assimilation (DA) is a methodology for combining mathematical models simulating complex systems (the background knowledge) and measurements (the reality or observational data) in order to improve the estimate of the system state (the forecast). The DA is an inverse and ill posed problem usually used to handle a huge amount of data, so, it is a large and computationally expensive problem. Here we focus on scalable methods that makes DA applications feasible for a huge number of background data and observations. We present a scalable algorithm for solving variational DA which is highly parallel. We provide a mathematical formalization of this approach and we also study the performance of the resulted algorith

Numerical Solution of Diffusion Models in Biomedical Imaging on Multicore Processors

In this paper, we consider nonlinear partial differential equations (PDEs) of diffusion/advection type underlying most problems in image analysis. As case study, we address the segmentation of medical structures. We perform a comparative study of numerical algorithms arising from using the semi-implicit and the fully implicit discretization schemes. Comparison criteria take into account both the accuracy and the efficiency of the algorithms. As measure of accuracy, we consider the Hausdorff distance and the residuals of numerical solvers, while as measure of efficiency we consider convergence history, execution time, speedup, and parallel efficiency. This analysis is carried out in a multicore-based parallel computing environment

Driving NEMO Towards Exascale: Introduction of a New Software Layer in the NEMO Stack Software

This paper addresses scientific challenges related to high level implementation strategies that leads NEMO to effectively use of the opportunities of exascale systems. We consider two software modules as proof-of-concept: the Sea Surface Height equation solver and the Variational Data Assimilation system, which are components of the NEMO ocean model (OPA). Advantages rising from the introduction of consolidated scientific libraries in NEMO are highlighted: such advantages concern both the "software quality" improvement (see the software quality parameters like robustness, portability, resilence, etc.) and time reduction of software development