singular matrix

Matthew Knepley knepley at
Thu Apr 16 10:34:58 CDT 2009

On Thu, Apr 16, 2009 at 10:22 AM, Yixun Liu <enjoywm at> wrote:

> Hi,
> For Ax=b, A is mxn, m>n. I use CG to resolve it and find the solution
> makes no sense.  I guess rank(A) < min(m,n). How to resolve this
> singular system? Use SVD?

CG is a method for SPD matrices. This matrix is not symmetric. You appear
to be solving a least squares problem. I would read about these a little.
Bjorck has a pretty good book.


> Best,
> Yixun
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
-- Norbert Wiener
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the petsc-users mailing list