Fast Explicit Diffusion (FED).

References:

• Fast Explicit Diffusion (FED) and Fast-Jacobi (FJ):
  http://www.mia.uni-saarland.de/Research/SC_FED.shtml

• S. Grewenig, J. Weickert, C. Schroers, A. Bruhn:
  "Cyclic Schemes for PDE-Based Image Analysis"
  Technical Report No. 327, Department of Mathematics, Saarland University, Saarbrucken, Germany, March 2013.

• S. Grewenig, J. Weickert, A. Bruhn:
  "From box filtering to fast explicit diffusion"
  In M. Goesele, S. Roth, A. Kuijper, B. Schiele, K. Schindler (Eds.): Pattern Recognition.
  Lecture Notes in Computer Science, Vol. 6376, 533-542, Springer, Berlin, 2010.