Improvements of the particle-in-cell code EUTERPE for petascaling machines

EUTERPE is a Lagrangian or particle-in-cell (PIC) gyrokinetic code for the simulation of fusion plasma instabilities. The aim of this code is to address global linear and nonlinear simulations of fusion plasmas in threedimensional geometries, in particular in stellarators. EUTERPE, like other gyrokinetic codes, is at the forefront of plasma simulations and requires a huge amount of computational resources. It has been developed at CRPP and IPP as a parallel code, using Message Passing Interface (MPI), and has been adapted to different computing platforms. The Fusion Theory unit from CIEMAT collaborates with the IPP and the Barcelona Supercomputing Center (BSC) for the development and exploitation of this code. The code solves the Vlasov equation in connection with the equation of motion for the particles and the quasineutrality equation on a real space grid [1, 2, 3]. The code provided good results both in linear and nonlinear simulations of Ion Temperature Gradient (ITG) instabilities carried out in screw-pinch geometry [4]. In those simulations, especially for the nonlinear ones, it became clear that the amount of computational resources that a global threedimensional PIC code requires for typical simulations is huge, and it is of crucial importance that it can run efficiently on multi-processor architectures. Previously, the code had been heavily optimized and its scaling had