[petsc-dev] -ksp_view_binary with DA vectors

[Jed Brown]

On Tue, 22 Jun 2010 11:30:47 -0500, Barry Smith <bsmith at mcs.anl.gov> wrote:
>     Actually we should add the same support for matrices and then the inconsistency would disappear.

Is this actually useful?  I.e. would anyone actually want to work with
the matrix in natural ordering?  If you read it in parallel, you'll get
"slabs" instead of blocks".  If you have a different number of processes
than you started with, the old blocks at least provide a quasi-sensible
partition.  Even if you read it in serial, the standard partition should
still have better memory locality.

But perhaps the issue is not performance, but just being able to easily
compare matrices assembled on a different number of processes.  That
does seem useful, but it seems like a fairly involved thing to
implement.  I think I'd rather just put 1:N in the vector (in the
natural ordering) and apply that permutation from Matlab.

Jed