[petsc-users] question about DA

[Likun Tan]

Thanks.

What is the difference between DACreate2d() and DMDACreate2d()? I found
the definitions of these two are the same.




On Sat, August 27, 2011 5:16 pm, Barry Smith wrote:
>

> You cannot just split a 2d array among some processes and a 3d array
> across the same processes and expect somehow that the layouts of two of
> the indices will match between the two arrays.
>
> You can run, for example with -da_view to see how they two arrays are
> being laid out in parallel by default. You will need set certain values
> in the m,n, and p arguments to DMDACreate2d() and 3d to get layouts that
> match. Note that these are not the M,N, and P arguments.
>
> Barry
>
>
>
> On Aug 27, 2011, at 4:09 PM, Likun Tan wrote:
>
>
>> the size of temp and H is 9*9*201, the size of S is 9*9.
>>
>> I used 2 processors, the returned values are
>> temp: 0 0 0 9 9 101
>> temp: 0 0 101 9 9 100
>> H: 0 0 101 9 9 100
>> S: 0 5 101 9 4 100
>>
>>
>> I am not sure what you mean by how DAs were constructed, the command i
>> used for construction is: DACreate2d(PETSC_COMM_WORLD, DA_NONPERIODIC,
>> DA_STENCIL_STAR, 9, 9,
>> PETSC_DECIDE, PETSC_DECIDE, 1, 0, PETSC_NULL, PETSC_NULL, &da2D);
>> DACreate3d(PETSC_COMM_WORLD, DA_NONPERIODIC, DA_STENCIL_STAR, 9, 9, 201,
>>  PETSC_DECIDE, PETSC_DECIDE, PETSC_DECIDE, 1, 0, PETSC_NULL,
>> PETSC_NULL,
>> PETSC_NULL, &da3D);
>>
>>
>> i got some sense of the problem after watching m, n, p, but i don't
>> know how to avoid it.
>>
>> On Sat, August 27, 2011 4:53 pm, Jed Brown wrote:
>>
>>> On Sat, Aug 27, 2011 at 15:49, Likun Tan <likunt at andrew.cmu.edu>
>>> wrote:
>>>
>>>
>>>
>>>> I attached my code again, p was used in defining temp and H, when
>>>> defining S, we don't need p and zs:
>>>>
>>>>
>>>
>>> You need p to know the limits of the integral. You need that the
>>> domain not be decomposed in the z direction if you are going to
>>> integrate without doing communication. You still haven't shown us how
>>> the DAs were constructed or what the returned values for
>>> (xs,ys,zs,m,n,p) were when got
>>> them from da3D and what (xs,ys,m,n) were when you got them from da2D.
>>>
>>
>>
>>
>>
>
>
>