[petsc-users] Does PETSc have some functions like A.*B, A./B in Matlab?

[Jed Brown]

On Sun, 21 Feb 2010 13:48:09 -0600, Yujie <recrusader at gmail.com> wrote:
> Hi, Jeb
> 
> It looks MatGetRow() only can get the nonzero row values for sparse matrix.
> It is not suitable for A./B if there are different formats between A and B.

Of course, but note that B must have at least all the nonzeros of A,
otherwise you divide by 0.  If you really need to do A./B where A was
not preallocated to match B (it is a strict subset), then MatDuplicate B
(call it C), loop over rows inserting rows of A into C, then perform the
division with MatGetArray B and C (you'll have to work with the
off-diagonal blocks separately in parallel).

But you would be *much* better off to find a way to assemble the matrix
you want rather than these other matrices with inequivalent nonzero
patterns.

Jed