Fig 3 - uploaded by Michele Benzi
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Spectra of H P corresponding to P T for γ = −1 (left), γ = 1 (center) and γ = 2 (right). Top: Left preconditioning. Bottom: Right preconditioning (problem size 2555).
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Context 1
... in Figure 3 we display the spectra of the symmetric parts of the preconditioned matrices for different values of γ using left and right preconditioning with P T , with problem size 2555. Note that using γ = 1 and right preconditioning leads to an indefinite precondi- tioned matrix. ...
Context 2
... Tables 6 and 7 we report the results for GMRES with the "exact" P T preconditioner for right and left preconditioning, respectively. The latter results are included to show that no significant difference is noticeable compared to the right preconditioned case, and also because of the nice clustering properties shown in Table 1 and Figure 3. The results for FGMRES and inexact application of P T are shown in Table 8. ...
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