Are you thinking of using PCSetModifyMatrices()? Actually, this brings up another issue (now on petsc-dev). Should this callback be attached to a Mat, instead of a PC? Then MatGetSubMatrices() can use this callback on each of the extracted submatrices, if necessary. In the case of a KKT system, it would then set the nontrivial block size on the primal submatrix.
Dmitry. On Wed, Apr 11, 2012 at 3:33 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote: > The original matrix might not have blocks, but that does not mean that a > submatrix does not have blocks. > On Apr 11, 2012 3:30 PM, "Mark F. Adams" <mark.adams at columbia.edu> wrote: > >> >> On Apr 11, 2012, at 11:24 AM, Jed Brown wrote: >> >> On Wed, Apr 11, 2012 at 12:01, Mark F. Adams <mark.adams at >> columbia.edu>wrote: >> >>> eed to know the block size (eg, 4). I get this info by having the user >>> set the block size of the matrix. This is what you should do for the >>> non-contact test. This will not work with contact equations ... or at >>> least it does not make sense. How can I get this info? >>> >>> 1) hard wire it: if I see 7 vectors then bs=4. >>> >> >> Hell no. >> >> >>> >>> 2) have setNearNullSpace take a block size, and set the vector block >>> size, which I can get like I do from the matrix now. >>> >> >> No. >> >> When you call MatGetSubMatrix(), you will get back a matrix that has a >> near null space (and a block size if that happens to be relevant; there >> will not be a block size if deformation and thermodynamics are in different >> spaces). Don't worry about how that is done, just call MatGetSubMatrix(). >> >> >> OK, I don't see how you know that the block size is 4 ... do you call >> MatSetBlockSize even if there are constraints that are not blocked? >> >> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120411/1a587cf7/attachment.html>
