The two-grid algorithm confronts a shifted unitary orthogonal method
Boriçi, A · CERN Document Server (European Organization for Nuclear Research) · 2004
In this paper I describe a new optimal Krylov subspace solver for shifted unitary matrices called the Shifted Unitary Orthogonal Method (SUOM). This algorithm is used as a benchmark against any improvement like the two-grid algorithm. I use the latter to show that the overlap operator can be inverted by successive inversions of the truncated overlap operator. This strategy results in large gains compared to SUOM.