Randall Mackie <[email protected]> writes: > Dear PETSc users - > > I am trying to create a block matrix but it is not clear to me what is the > right way to do this. > > First, I create 2 sparse matrices J1 and J2 using two different DMDAs. > Then I compute the products J1^T J1, and J2^T J2, which are different sized > matrices. > > Since the matrices are already constructed and built, what is the best way to > place those matrices into a block matrix?
Block diagonal or are they coupled? > Does it work to create a composite DM, call DMCreateMatrix on the composite > DM, then call MatGetLocalSubMatrix on the blocks, then simply do a MatCopy? If the matrices are already assembled and there is no going back on that, it'd be easiest to use MatNest and then MatConvert (if you don't want a split solver).
