[petsc-dev] Size of " PetscInt *garray" in Mat_MPIAIJ

[Jed Brown]

Fande Kong via petsc-dev <petsc-dev at mcs.anl.gov> writes:

> Hi Developers,
>
> What is the size of " PetscInt *garray" in Mat_MPIAIJ?  Will it be
> mat->B->cmap->N? 

Yes.

> If so, it is not scalable in terms of the problem size, right? I am
> missing something here.

No, B only has columns for off-process entries where there are nonzeros.
It's only a scalability issue if you have dense rows, in which case you
have bigger problems on communication and should not use 1D matrix
decompositions.