[petsc-users] Using /src/ksp/ksp/example/tutorial/ex29.c to solve Poisson Equation Twice

[Alan Wei]

That's great, Matt. Thanks to point out the example for me.

best,
Alan

On Mon, Oct 3, 2011 at 12:06 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, Oct 3, 2011 at 12:00 PM, Alan Wei <zhenglun.wei at gmail.com> wrote:
>
>> Dear all,
>>     I still have the problem. >_<
>>     I can not find the DMMG interface provided to change the RHS,
>> mentioned by Dr. Smith. The only thing I have is DMMGSetKSP(). It is
>> DMMGSetKSP(dmmg,ComputeRHS,ComputeMatrix).When I use it first time in
>> this example, it calls both ComputeRHS and ComputeMatrix (I assert some
>> print-out probes inside these two functions). However, If I use it again, it
>> just does not call the new one; rather, it calls the old one.
>>      My code is attached. Could you please help me to fix this problem
>> ^_^.
>>
>
> Yes, this is the way DMMG works. It can only be setup once. This is a
> severe limitation, which is why we
> have discontinued its use. If you look at ex50.c, we show how to transform
> ex19 into a code using SetDM
> instead of DMMG. You can then reset the DMDA rhs function at each
> iteration.
>
>   Thanks,
>
>      Matt
>
>
>> best,
>> Alan
>>
>> On Sun, Oct 2, 2011 at 5:52 PM, Alan Wei <zhenglun.wei at gmail.com> wrote:
>>
>>> In this example, i recalled the ComputeRHS.
>>>
>>> Alan
>>>
>>>
>>> On Sun, Oct 2, 2011 at 5:22 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>>
>>>> On Sun, Oct 2, 2011 at 16:31, Alan Wei <zhenglun.wei at gmail.com> wrote:
>>>>
>>>>> BTW, what is the DMMG interface you are talking about? is it
>>>>> DMMGSetKSP()?
>>>>
>>>>
>>>> Every object and function containing "DMMG" will be removed. (I don't
>>>> think we've decided on a precise timeline, but don't write new code that
>>>> uses DMMG.)
>>>>
>>>>
>>>>> if so, that's is my problem. At the 2nd time of using DMMGSetKSP() in
>>>>> the main function, it does not call the __function__ to compute the right
>>>>> hand side. >_< any suggestions on that?
>>>>
>>>>
>>>> What function is being called?
>>>>
>>>
>>>
>>
>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
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