Folded_spectrum_method
Folded spectrum method
Mathematical method for solving large eigenvalue problems
In mathematics, the folded spectrum method (FSM) is an iterative method for solving large eigenvalue problems. Here you always find a vector with an eigenvalue close to a search-value . This means you can get a vector in the middle of the spectrum without solving the matrix.
, with and the Identity matrix.
In contrast to the Conjugate gradient method, here the gradient calculates by twice multiplying matrix