Improving Inversions of the Overlap Operator
  We present relaxation and preconditioning techniques which accelerate the inversion of the overlap operator by a factor of four on small lattices, with larger gains as the lattice size increases. These improvements can be used in both propagator calculations and dynamical simulations. 
S. Krieg, N. Cundy, J.van den Eshof, A. Frommer, Th. Lippert, K.   Sch\"afer