semba-fdtd is a finite-differences in time domain solver with special focus on EMC problems. semba-fdtd can be used as a standalone solver or integrated within a FreeCAD workbench (www.elemwave.com).
With increasing number of time steps, spice simulations take more time per time step. It is under investigation. The most likely cause at this point is the stop/resume dynamic needed to pair the mtln steps with the spice steps. It makes simulations with many time steps inviable
In the grid starting from a delta_initial and ending into a delta_final create a set of gridding lines according to a geometric progression of grid lines separated as a geometric progression. The input should be only the initial and final delta, and the algorithm should find the number of cells and ratio of the progression.