[petsc-users] Memory usage with DMDACreate3d and DMDAGetCorners

[Matthew Knepley]

On Tue, Nov 10, 2015 at 6:34 AM, TAY wee-beng <zonexo at gmail.com> wrote:

>
> On 10/11/2015 8:25 PM, Matthew Knepley wrote:
>
> On Tue, Nov 10, 2015 at 1:33 AM, TAY wee-beng <zonexo at gmail.com> wrote:
>
>> Hi,
>>
>> I need a subroutine in Fortran to partition a subset of my grid in the 3
>> x,y,z directions for MPI. I thought of using DMDACreate3d and
>> DMDAGetCorners to get the starting and width of the partitioned grid.
>>
>> Because I need to partition at every time step and the subset grid
>> changes dimension and index at every time step, so I will also need to use
>> DMDestroy after each time step
>>
>> Will that use alot of memory? Will the grid actually be created? So I
>> wonder if this DMDACreate3d and DMDestroy calls will take a lot of time.
>
>
> DMDA just does 1D partitioning in each dimension, so its not that
> sophisticated. Is that all you want?
>
>   Matt
>
> Hi,
>
> Ya, that's all I want. Btw, how does DMDACreate3d partition the grids in
> x,y,z? What is the algorithm behind it?
>
> Supposed I have 14 x 17 x 20 and 12 cores. How does DMDACreate3d partition
> it?
>

https://bitbucket.org/petsc/petsc/src/b0bc92c60ab2e8c65b1792a9a4080bf92080e52f/src/dm/impls/da/da3.c?at=master&fileviewer=file-view-default#da3.c-231

  Thanks,

     Matt


> Thanks.
>
>
>
>>
>> --
>> Thank you.
>>
>> Yours sincerely,
>>
>> TAY wee-beng
>>
>>
>
>
> --
> 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
>
>
>


-- 
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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