The local indices of the local mesh and local vectors, which includes ghost
vertices. There are global-to-local methods to fill in ghost values and
local-to-global methods to create global vectors that you can use for
computation.
On Mon, Nov 19, 2018 at 5:16 PM Sajid Ali
wrote:
> Bingo!
>
>
Bingo!
So, DMDAGetElements gives the indices of the mesh, right ?
Thank you !
You seem to be confusing the degree of the mesh and the "degree" of the
matrix and vector.
A matrix is always N x M (2D if you like), a vector is always N (or 1 x N,
or 1D if you like).
The mesh in a DM or DA can be 1, 2 or 3D.
On Mon, Nov 19, 2018 at 4:44 PM Sajid Ali via petsc-users <
So, DMDA is used for sparse matrices arising from FD/FE and MatCreateMPIAIJ
can be used for dense matrices (though it is strongly discouraged).
My confusion stemmed from DMDAGetElements giving the element indices for
the 1D mesh/vector of size N(when the DMDACreate1d is used). But these
indices
> On Nov 19, 2018, at 3:30 PM, Sajid Ali
> wrote:
>
> I think what confused me was the fact that using DMCreateMatrix(da,)
> created a 12x12 matrix with 144 elements but summing up nel*nen from each
> rank gives only 2*2+3*2+3*2+3*2=20 elements. So this means that
> DMDAGetElements
I think what confused me was the fact that using DMCreateMatrix(da,)
created a 12x12 matrix with 144 elements but summing up nel*nen from each
rank gives only 2*2+3*2+3*2+3*2=20 elements. So this means that
DMDAGetElements returns the elements for the vector created on the mesh and
this happens to
Hi Barry,
> Le 15 nov. 2018 à 18:16, Smith, Barry F. a écrit :
>
>
>
>> On Nov 15, 2018, at 4:48 AM, Appel, Thibaut via petsc-users
>> wrote:
>>
>> Good morning,
>>
>> I would like to ask about the importance of the initial choice of ordering
>> the unknowns when feeding a matrix to
>
>
>
> Mark would have better comments on the scalability of the setup stage.
>
>
The first thing to verify is that the algorithm is scaling. If you coarsen
too slowly then the coarse grids get large, with many non-zeros per row,
and the cost of the matrix triple product can explode. You can
Dear Matthew,
using either "-build_twosided allreduce" or "-build_twosided redscatter"
workarounds the Intel MPI internal error!
Besides, with Intel MPI, the weak scaling figures look like:
**preconditioner set up**
[0.8865120411, 2.598261833, 3.780511856]
**PCG stage**
[0.5701429844,
