On Tue, Oct 11, 2011 at 11:15 AM, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com">knepley@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;">
<div class="im">On Tue, Oct 11, 2011 at 11:13 AM, behzad baghapour <span dir="ltr"><<a href="mailto:behzad.baghapour@gmail.com" target="_blank">behzad.baghapour@gmail.com</a>></span> wrote:<br></div><div class="gmail_quote">
<div class="im"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Okey. I checked the condition number "max/min".<br>It increases significantly in each ksp iterations!!!<br></blockquote><div><br></div></div><div>The approximation is becoming better. The condition number is harder to actually compute than the solution.</div>
<div><br></div><div>Bottom line: You have a hard problem. Iterative methods do not work on hard problems without specialized</div><div>preconditioners. I recommend a literature search on solvers for your equations.</div>
<div><br></div></div></blockquote><div><br></div><div>From what he said earlier,</div><div><br></div><div>> <span class="Apple-style-span" style="color: rgb(51, 51, 51); font-family: arial, sans-serif; font-size: 13px; background-color: rgb(255, 255, 255); ">I have solved my problem before with some other solvers (gmers/ILU(2)) and the </span></div>
<div><span class="Apple-style-span" style="color: rgb(51, 51, 51); font-family: arial, sans-serif; font-size: 13px; background-color: rgb(255, 255, 255); ">> convergence has been achieved within 15 - 16 iterations.</span> </div>
<div><br></div><div>it sounds like he should try using <font class="Apple-style-span" color="#333333" face="arial, sans-serif">one of Hypre's ILUs. </font></div><div><font class="Apple-style-span" color="#333333" face="arial, sans-serif"><a href="http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-dev/docs/manualpages/PC/PCHYPRE.html">http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-dev/docs/manualpages/PC/PCHYPRE.html</a></font></div>
<div><font class="Apple-style-span" color="#333333" face="arial, sans-serif"><br></font></div><div><font class="Apple-style-span" color="#333333" face="arial, sans-serif">Bezhad, why start with Jacobi if you already knew that GMRES+ILU(2) works?</font></div>
<div><font class="Apple-style-span" color="#333333" face="arial, sans-serif"><br></font></div><div><font class="Apple-style-span" color="#333333" face="arial, sans-serif">Jack</font></div></div>