<div dir="ltr">On Thu, Feb 28, 2013 at 7:19 PM, Zhenglun (Alan) Wei <span dir="ltr"><<a href="mailto:zhenglun.wei@gmail.com" target="_blank">zhenglun.wei@gmail.com</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear folks,<br>
Here are several questions following up my previous ones:<br>
1, I modified my code based on ex49.c. However, I found that if I don't call 'DMDASetUniformCoordinates' before calling 'DMDAVecGetArray', then an error comes up:<br>
[0]PETSC ERROR: Null argument, when expecting valid pointer!<br>
[0]PETSC ERROR: Null Object: Parameter # 2!<br>
The code do works if I add a call for 'DMDASetUniformCoordinates' in it. However, I feel it is a waste of calling 'DMDASetUniformCoordinates' since what follows this calling is to change the coordinate to a non-uniform gird. Does it have any way to bypass this call or you think it is fine to keep it here.<br>
</blockquote><div><br></div><div style>If you do not call it, then you have to create the coordinate vector yourself. I would just call it.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
2, Also, if I do by this way, the outputted mesh looks weird, as shown in the figure.<br>
I was trying to double the dy value manually in the SetNonUniformGrid(). However, the only mesh changed is just on the z=0 and x=0 plane. Here I attached my code. Do I need to do anything else except DMDAVecRestoreArray() after I modified the coordinate information?<br>
</blockquote><div><br></div><div style>I do not understand what you want here.</div><div style><br></div><div style> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
thanks,<br>
Alan<br>
<br>
<br>
On 2/26/2013 8:46 PM, Barry Smith wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Feb 26, 2013, at 4:49 PM, "Zhenglun (Alan) Wei"<<a href="mailto:zhenglun.wei@gmail.com" target="_blank">zhenglun.wei@gmail.com</a>> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Dear folks,<br>
I have one question for the ex49.<br>
It do show a way to 'get' the 'coord' by the 'DMDAVecGetArray'. Should I just modified the coordinate on the 'coord' in order to obtain a non-uniform grid? and then, use DMDAVecRestoreArray to link the modified 'coord' back to 'cda' so that the 'coord' will be updated to the mesh I want?<br>
</blockquote>
Yes, you can do this.<br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
thanks,<br>
Alan<br>
<br>
On 2/22/2013 3:20 PM, Matthew Knepley wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Fri, Feb 22, 2013 at 3:57 PM, Zhenglun (Alan) Wei<<a href="mailto:zhenglun.wei@gmail.com" target="_blank">zhenglun.wei@gmail.com</a>> wrote:<br>
Dear all,<br>
I hope you're having a nice day.<br>
I wonder if anyone could point out a example for me about the<br>
DMDASetCoordinates(). I found this<br>
(<a href="http://www.mcs.anl.gov/petsc/petsc-current/src/dm/impls/da/dacorn.c.html#DMDASetCoordinates" target="_blank">http://www.mcs.anl.gov/petsc/<u></u>petsc-current/src/dm/impls/da/<u></u>dacorn.c.html#<u></u>DMDASetCoordinates</a>)<br>
online; however it does not really demonstrate how to create the<br>
'coordinate vector - c'.<br>
Also, I found that in the petsc sub-folder:<br>
/petsc-dev/src/dm/impls/patch has a patch.c, which I suppose that it<br>
does a local refinement for mesh. Does this a mature model that we can<br>
use or just a testing code?<br>
<br>
Look at KSP ex49. In the routine DMDACoordViewGnuplot2d() it reads out the coordinates.<br>
You could just as easily set them in this fashion.<br>
<br>
Matt<br>
thanks,<br>
Alan<br>
<br>
On 11/7/2012 6:55 PM, Barry Smith wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
On Nov 7, 2012, at 6:50 PM, Alan<<a href="mailto:zhenglun.wei@gmail.com" target="_blank">zhenglun.wei@gmail.com</a>> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Dear folks,<br>
I hope you're having a nice day.<br>
I'm testing the Poisson solver in /src/ksp/ksp/examples/<u></u>tutorials/ex45.<br>
It uses the 'DMDACreate3d' to generate a Cartisian structured grid and<br>
solve it with uniform grid size. However, I attempt to modify it to<br>
obtain solution with a Cartsian structured grid and non-uniform grid (It<br>
is not unstructured local refined mesh). Should I still use the<br>
'DMDACreate3d' and implement different grid size in 'ComputeMatrix' and<br>
'ComputeRHS'? In other words, does 'DMDACreate3d' itself include any<br>
mesh size information?<br>
</blockquote>
You can use DMDASetCoordinates() and DMDAGetCoordinates() (called DMSetCoordinates() and DMGetCoordinates() in petsc-dev) to keep track of the coordinates but you are responsible for generating the correctly scaled entries in the matrix etc.<br>
<br>
Barry<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
thanks,<br>
Alan<br>
</blockquote></blockquote>
<br><span class="HOEnZb"><font color="#888888">
<br>
-- <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>
</font></span></blockquote></blockquote></blockquote>
<br>
</blockquote></div><br><br clear="all"><div><br></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
</div></div>