<div class="gmail_quote">On Wed, Aug 24, 2011 at 14:11, Likun Tan <span dir="ltr"><<a href="mailto:likunt@andrew.cmu.edu">likunt@andrew.cmu.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":16r">I am solving a linear equation Ax=0 with Petsc.<br>
Previously i was following Numerical Recipe and using LU decomposition,<br>
for a non-singular matrix A, x should be zero. By applying LU in Recipe, i<br>
got x=0.<br>
When i solve it with ksp, x is some small value to the power of -9.</div></blockquote></div><br><div>This is normal. You can make it more accurate by reducing the tolerance, e.g. -ksp_rtol 1e-12.</div>