On Thu, Feb 19, 2009 at 3:22 PM, Randall Mackie <span dir="ltr"><<a href="mailto:rlmackie862@gmail.com">rlmackie862@gmail.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I'm trying to modify my code to use the DMMG routines to solve my system<br>
by multi-grid, instead of the usual krylov solver. In my previous code,<br>
I would set up a DA for my finite difference grid, set the matrix<br>
preallocation using MATCreateMPIAIJ, then fill the matrix, etc.<br>
<br>
In the code I've modified to use DMMG, here is my sequence of routines<br>
so far:<br>
<br>
call DMMGCreate(...)<br>
call DACreate3D(....) ! to set the DA on the finest level<br>
call DMMGSetDM(...)<br>
<br>
<br>
call DMMGSETKSP(...)<br>
<br>
<br>
Questions:<br>
<br>
1) I want to set the DA on the finest level and use Galerkin to get<br>
the coarser matrices. So, is the DACreate above the way to do this?</blockquote><div><br>Unfortunately, the DA has no way to do this right now since it does not<br>know how to coarsen. You tell it the coarse grid and it refines.<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
2) How do I set the matrix preallocation here for use in the DMMG routines?<br>
Would I use the same MATCreateMPIAIJ as before, and if so, where do I<br>
put that? In the routine that fills the Jacobian, or in the main program<br>
someplace?</blockquote><div><br>The DA will doe the preallocation by default. Use DAGetMatrix().<br><br> Matt<br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Thanks, Randy<br>
</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>