Doubts about SNESMF and matrix-free preconditioners

Tue Nov 18 13:22:13 CST 2008

Originally, my idea is to implement this
preconditioner<http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TY8-4MS9JN4-C&_user=686358&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000037498&_version=1&_urlVersion=0&_userid=686358&md5=8ae14f3bace78503c283f15cc0adc533>.
As far as I`m concerned, there`s no need to form and store any matrices,
only the diagonal elements of the jacobian like I said. This way, I believe
I`d have to stick with option #2.

With regard to "The matrix it will receive will be the MFFD that is created
by -mat_mf.", what matrix is that actually? The one that is created by the
`MatCreateMFFD` routine?

"Then you would have to extract the KSP and set your matrix-free PC there."

Do the calls to PCSetType and PCShellSetApply plus my own implementation of
the `MatrixFreePreconditioner` function do that?

Best regards,

Rafael
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