SIAM Journal on Scientific Computing
Flexible GMRES with Deflated Restarting
SIAM Journal on Scientific Computing
GMRES with adaptively deflated restarting and its performance on an electromagnetic cavity problem
Applied Numerical Mathematics
Combining analytic preconditioner and Fast Multipole Method for the 3-D Helmholtz equation
Journal of Computational Physics
Accelerated GCRO-DR method for solving sequences of systems of linear equations
Journal of Computational and Applied Mathematics
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In general, restarting the generalized minimum residual method (GMRes) slows down the convergence speed. There exist a number of methods that improve the convergence of restarted GMRes. One of them is GMRes with deflated restarting [SIAM J. Sci. Comput., 24 (2002), pp. 20-37] introduced by Morgan. This method retains a number of harmonic Ritz vectors at each restart to mitigate convergence slowdown. We investigate the accuracy of this method and propose a slight modification of it that is mathematically equivalent. We show that the new implementation has better numerical properties, especially if high accuracy of the solution is required. Numerical results are presented that confirm our theoretical results.