Optimization of a kinetic laser-plasma interaction code for large parallel systems

In this work, we simulate the interaction between intense laser radiation and a fully ionized plasma by solving a Vlasov-Maxwell system using the "Particle-In-Cell" (PIC) method. This method provides a very detailed description of the plasma dynamics, but at the expense of large computer resources.Our SPMD 3D PIC code, CALDER, which is fully relativistic, is based on a spatial domain decomposition. Each processor is assigned one subdomain and is in charge of updating its field values and particle coordinates. This paper presents some optimizations to achieve large simulations, such as communication overlapping, cache-friendly data management, and the use of a parallel sparse PCG solves the Poisson's equation.Finally we present the benefits from these optimizations on the IBM SP3 and the physical results for a large case simulation obtained on the CEA/DIF Teraflops parallel computer.