Orthogonal Method for Linear Systems. Preconditioning

The complexity of an orthogonal method for solving linear systems of equations is discussed. One of the advantages of the orthogonal method is that if some equations of the initial linear system are modified, the solution of the resulting system can be easily updated with a few extra operations, if the solution of the initial linear system is used. The advantages of this procedure for this updating problem are compared with other alternative methods. Finally, a technique for reducing the condition number, based on this method, is introduced.