[petsc-users] Memory usage with DMDACreate3d and DMDAGetCorners

[TAY wee-beng]

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 
> <mailto: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?

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

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