If you are doing FEA, then you should have the element connectivity data
available from the input. From this it is an easy task to compute the
the assembly pattern and hence the precise allocation data, dnz and
onz. There should be no need to perform a 'trial' assembly.
-sanjay
On 1/18/18 8:49 PM, saturday luis wrote:
Hi PETSc team:
Is there a way to make precise matrix preallocation for an
unstructured grid (I am not using the DMPlex object). Or do you have
any example code for estimating the dnz & onz data?
On top of my head, I can do a two-phase calculation. I can first give
a rough estimate and do one finite element assembly, then I will call
MatGetRow to locate the column indices for nonzero entries. Then in
the second step, I will destroy the Mat and create a new Mat with this
obtained sparsity pattern.
Do you have any suggestions?
Thanks!
Luis
