On Sat, Jun 25, 2011 at 2:49 PM, NAN ZHAO <span dir="ltr"><<a href="mailto:zhaonanavril@gmail.com">zhaonanavril@gmail.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Dear all,<div><br></div><div>I have a question about how to use the ksp in a smart way to solve a linear system. I had a simple test to generate a random matrix and vector, but I put only one nonzero value in a row (let's say 1), and in the respect location of the RHS vector I put a zero. The size of the matrix is kind of big, I saw petsc some time give unreasonable value at that loaction (it should be zero or some really small number). I want to know if there is a way to avoid it?</div>
</blockquote><div><br></div><div>The problem sounds degenerate. A full rank A with 1 nonzero/row and b = 0 would not have a solution other than 0. What will this tell you?</div><div><br></div><div> Matt</div><div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div>Thanks</div></blockquote></div>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>