<div class="gmail_quote">On Thu, Sep 8, 2011 at 14:58, Tian(ICT) <span dir="ltr"><<a href="mailto:rongtian@ncic.ac.cn">rongtian@ncic.ac.cn</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div><font size="2">By 50 iterations, I meant my implementation of this prescribed
boundary condition was not working,</font></div>
<div><font size="2">not converging. Yes, I put 1 on the diagonal.\</font></div></blockquote><div><br></div><div>Is the system singular? What equations are you solving? Do boundary conditions give you a constant null space? Incompressible flow is this way.</div>
<div><br></div><div>Run with -ksp_monitor_true_residual -pc_type lu -snes_view and send the output.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div><font size="2"></font><br></div>
<div>Can I just enforce the solution x within each Newton iteration to the
prescribed values to satisfy the prescribed boundary condition, not
MatZeroRowsing Jacobian?</div></blockquote></div><br><div>It's important for the linear system to be nonsingular.</div>