  We consider the Fast Fourier Transform (FFT) based numerical method for thin
film magnetization problems [Vestg{\aa}rden and Johansen, SuST, 25 (2012)
104001], compare it with the finite element methods, and evaluate its accuracy.
Proposed modifications of this method implementation ensure stable convergence
of iterations and enhance its efficiency. A new method, also based on the FFT,
is developed for 3D bulk magnetization problems. This method is based on a
magnetic field formulation, different from the popular h-formulation of eddy
current problems typically employed with the edge finite elements. The method
is simple, easy to implement, and can be used with a general current-voltage
relation; its efficiency is illustrated by numerical simulations.
