Luc Berger-Vergiat <[email protected]> writes: > Hi all, > I would like to know if there would be an easy way of computing the Sp > preconditioner for a fieldsplit schur complement using the following > formula: > Sp=A11-A10*diag(inv(A00))*A01 > instead of > Sp=A11-A10*inv(diag(A00))*A01
Not in general because inv(A00) is dense, thus not practically computable. You can use PCFieldSplitSetSchurPre to provide your own Sp. > I think that it would be really beneficial in my case since the > eigenvalues of both operators are very different for my problem (see > ev_S_diaginv for the eigenvalues of the modified Sp and ev_S for the > eigenvalues of the current Sp). > > I do understand that this requires to compute a more complex inverse > while forming Sp, but I compute this inverse using a block jacobi lu due > to the special properties of my matrix (see jac_nonlin_nested for the > sparsity pattern of my matrix). So the change would actually be quite > minimal no? I am also actually debating whether I should compute the > exact S? > > -- > Best, > Luc
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