<div class="gmail_quote">On Thu, Nov 10, 2011 at 02:00, Bao Kai <span dir="ltr"><<a href="mailto:paeanball@gmail.com">paeanball@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div dir="ltr">I guess the interface file is used to call the functions in umfpack to solve the linear system. But the default matrix format in umfack should be csc, and I did get how the interface handle this problem. <br>
</div></blockquote><div><br></div><div>So we give the CSR data structure to Umfpack which means that Umfpack sees the transpose. Then we use the transpose-solve functionality.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div dir="ltr"><br>I go forward to try some linear solvers now. <br>
<br>The matrix generated with my problem is a little poor, resulting from a mixed finite element method, asymmetric and indefinite. And the inclusion of irregular boundary makes it worse. This is actually one reason I began with a direct solver. <br>
<br>If you have any suggestions on solve this kinds of linear systems, please tell me. </div></blockquote></div><br><div>Start with a direct solver. Once you have things working, you can change the discretization of boundary conditions to be better conditioned and look at iterative solvers (which are somewhat technical for indefinite problems).</div>