There is a growing demand for and lack of ultrafast, memory sparing but rigorous light scattering calculation techniques at large planar 2D diffracting objects. Examples include diffraction in OPC and in real-time scatterometry. Our approach to these requirements is the Generalized Source Method (GSM) formulated in Fourier space and its ongoing improvement. In this conference contribution, we report on recent success by switching from CPU to GPU computations and by application of the scattering-vector (S-vector) algorithm
