This code is an implementation of the standard FFT homogenization method developed by Moulinec and Suquet (1998) for microstructures with linear elastic isotropic phases. It computes the effective (/homogenized) stiffness of a microstructure with two phases (in the code the inclusion has the shape of a cylinder).
By now, many different FFT homogenization methods have been developded, see for example
[1] J. Zeman, T.W.J. de Geus, J. Vondřejc, R.H.J. Peerlings, M.G.D. Geers. A finite element perspective on non-linear FFT-based micromechanical simulations. International Journal for Numerical Methods in Engineering, Accepted, 2016. arXiv: 1601.05970. [2] T.W.J. de Geus, J. Vondřejc, J. Zeman, R.H.J. Peerlings, M.G.D. Geers. Finite strain FFT-based non-linear solvers made simple. Submitted, 2016. arXiv: 1603.08893.
See also: https://github.com/tdegeus/GooseFFT where the basis of the codes in this repositoy can be found.