No optimizations Map. Map.+Simul.Comm. Map.+Simul.Comm. +Overlap(spectral) Map.+Simul.Comm. +Overlap(spectral+finite diff.) Problem size: (nx, ny, nz, nv, nμ, ns) = (256, 256, 32, 32, 32, 2) Parallelization: (Nxy, Nz, Nv, Nμ, Ns, Nthreads) = (4, 4, 4, 8, 2, 4) on BX900, (4, 4, 4, 4, 2, 8) on K Optimizations of a spectral/finite difference gyrokinetic code for improved strong scaling toward mill...