Hola Jesús
You were lucky you got 20x. See
https://petsc.org/release/docs/manualpages/Mat/MatSeqAIJSetPreallocation.html
https://petsc.org/release/docs/manualpages/Mat/MatMPIAIJSetPreallocation.html
Quote:
"For large problems you MUST preallocate memory or you will get
TERRIBLE performance,
"Ferrand, Jesus A." writes:
> Dear PETSc Team:
>
> I have a question about DM and PetscSection. Say I import a mesh (for FEM
> purposes) and create a DMPlex for it. I then use PetscSections to set degrees
> of freedom per "point" (by point I mean vertices, lines, faces, and cells). I
> then
Dear PETSc Team:
I have a question about DM and PetscSection. Say I import a mesh (for FEM
purposes) and create a DMPlex for it. I then use PetscSections to set degrees
of freedom per "point" (by point I mean vertices, lines, faces, and cells). I
then use PetscSectionGetStorageSize() to get
