[petsc-users] MatMPIBAIJSetPreallocationCSR i and j indices

[Lisandro Dalcin]

On 27 September 2013 21:23, Barry Smith <bsmith at mcs.anl.gov> wrote:
>  Just use MatCreateMPIBAIJWithArrays() saves thinking and work.

BTW, Have you ever thought about how hard to use is this API if you
want to provide the matrix values? How are users supposed to fill the
"values" array for a matrix with bs>1 ? This API is certainly not
Fortran-friendly (and I think it not even C-friendly). Mateo had the
CSR indices as well as the block values, but I recommended to use the
CSR indices to perform proper matrix preallocation, then loop over
cells and call MatSetValuesBlocked(). Otherwise, he would need to
create an new intermediate array and fill it the right way for
MatCreateMPIBAIJWithArrays() to work as expected.

The root of the problem is how MatSetValuesBlocked() expects the array
of values to be layout in memory. While I understand that the current
convention make it compatible with MatSetValues(), I'm always
wondering if a layout like values[nblockrows][nblockcols][bs][bs]
would not be much more convenient for users.



-- 
Lisandro Dalcin
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