  As a multi-purpose Particle-In-Cell (PIC) code, Smilei gathers many different
features in a single software. Combining some of them is challenging. In
particular, spectral solvers and patch based load balancing have a priori non
compatible requirements. This paper introduces the Single Domain Multiple
Decompositions (SDMD) method in order to address this issue. To do so,
different domain decompositions are used for fields and particles operations.
This approach allows to keep small domains for particles, necessary for a good
load balancing, while having large domains for the fields. It proves beneficial
in mitigating synchronization costs and gives the opportunity to introduce more
paralellism in the PIC algorithm on top of providing structures compatible with
spectral solvers.
