出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：he large systems of complex linear equations that are generated in QCD problems often have
multiple right-hand sides (for multiple sources) and multiple shifts (for multiple masses). Deflated
GMRES methods have previously been developed for solving multiple right-hand sides. Eigenvectors
are generated during solution of the first right-hand side and used to speed up convergence
for the other right-hand sides. Here we discuss deflating non-restarted methods such as BiCGStab.
For effective deflation, both left and right eigenvectors are needed. Fortunately, with the Wilson
matrix, left eigenvectors can be derived from the right eigenvectors. We demonstrate for difficult
problems with kappa near kc that deflating eigenvalues can significantly improve BiCGStab. We
also will look at improving solution of twisted mass problems with multiple shifts. Projecting
over previous solutions is an easy way to reduce the work needed.
