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shift PC for block solves #126

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colinjcotter opened this issue Jul 21, 2023 · 0 comments

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colinjcotter commented Jul 21, 2023 •

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a shift PC could help when lambda1/lambda2 has small real part.

To implement this, we provide another form Jp to use as the preconditioning operator.

In this form, we replace

lambda1 -> lambda2(max(real(lambda1/lambda2), e0) + 1j*imag(lambda1/lambda2))

where e0 is the real shift parameter. Then if the real part of lambda1/lambda2 is less than e0, it is shifted to e0.

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