[petsc-users] DMCreateMatrix with some dense row

[Sang pham van]

Thank you, Dave,

Can I just call My_DMCreateMatrix_DA_3d_MPIAIJ(DM da, Mat J, void*
my_context) when I need to create my matrix, and forget about
DMDASetGetMatrix()?

Thank you.

Pham

On Sat, Oct 24, 2015 at 1:33 PM, Dave May <dave.mayhem23 at gmail.com> wrote:

> If you need to access a user defined context from within your CreateMatrix
> function, you can attach it to the DM via PetscObjectCompose
>
>
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscObjectCompose.html
>
> If your context is not a petsc object, you can use PetscContainerCreate(),
>
>
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscContainerCreate.html#PetscContainerCreate
>
> You would then set your user context pointer inside the container and then
> use PetscObjectCompose() to attach the container to the DM
>
> Thanks,
>   Dave
>
>
> On 24 October 2015 at 06:04, Sang pham van <pvsang002 at gmail.com> wrote:
>
>> Hi Barry,
>>
>> The routine DMCreateMatrix_DA_3d_MPIAIJ has 2 input arguments (DM da,
>> Mat J), the function pointer in DMDASetGetMatrix() only accept function
>> with that two arguments.
>> As you suggested, I am writing a routine (based on DMCreateMatrix_DA_3d_MPIAIJ())
>> to preallocate the matrix in the way I wish, to do that I think It needs to
>> have one more input argument: My_DMCreateMatrix_DA_3d_MPIAIJ(DM da, Mat
>> J, void* my_context). But DMDASetGetMatrix() will not accept pointer of
>> this function. Please give a suggestion to overcome this.
>>
>> Thank you.
>>
>> Pham
>>
>>
>> On Fri, Sep 4, 2015 at 1:24 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>
>>>
>>>     Look at DMCreateMatrix_DA_2d_MPIAIJ  (or the 3d version if working
>>> in 3d)   You need to copy this routine and add whatever additional
>>> preallocation information you need.   Then call DMDASetGetMatrix()  so that
>>> the DM will use your routine to create the matrix for you.
>>>
>>>    Barry
>>>
>>>
>>>
>>>
>>> > On Sep 3, 2015, at 11:28 AM, Sang pham van <pvsang002 at gmail.com>
>>> wrote:
>>> >
>>> > Hi,
>>> >
>>> > I am using DMCreateMatrix to create matrix from a existed DM object
>>> and defined stencil.
>>> > In my code, boundary nodes need to involve many inner nodes, thus
>>> matrix rows corresponding to boundary nodes are almost dense. How can I
>>> tell petsc that those rows need to be preallocated with more entries? I
>>> don't want to use MatMPIAIJSetPreallocation() since advantages of DM might
>>> be lost.
>>> >
>>> > Many thanks.
>>> >
>>> > Sam.
>>> >
>>> >
>>>
>>>
>>
>
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