We present a performance portable implementation of the Spectral Ewald method, employing shared memory and streaming parallelism to rapidly evaluate periodic two-body potentials in Stokes flow. The method splits dense particle evaluation into near-field and far-field components, where the near-field is singular and the far-field decays rapidly in Fourier space. Far-field interactions resemble a Nonuniform Fast Fourier Transform: source potentials are interpolated onto a uniform grid (p2g), an ndFFT is applied, Fourier potentials are scaled, an ndIFFT is applied, and the potentials are interpolated back (g2p). The p2g, g2p, and near-field (p2p) interactions use Kokkos hierarchical parallelism with scratch-pad memory and thread-vector range reductions.
