[petsc-users] Block-ILU in Petsc

[Satish Balay]

On Fri, 14 Oct 2011, Jed Brown wrote:

> On Fri, Oct 14, 2011 at 09:09, behzad baghapour
> <behzad.baghapour at gmail.com>wrote:

> > 2- "the block size is the same the matrix block size" means that there is
> > no way to combine the matrix elements to build blocks of possible maximum
> > size like Hash method or something like this?
> >
> 
> For AIJ, there are "Inodes" which automatically detect identical rows where
> blocking can be used. This helps more or less, depending on the hardware.
> There is no such thing for BAIJ, but it wouldn't offer much improvement in
> memory performance anyway. BAIJ performance approaches dense mat-vec as long
> as the ordering is such that the vector can be reused.

I view AIJ+inode as variable-blocking in 1 dimenstion. Doing variable
blocking in 2 dimensions is perhaps very difficult - and not worth the
exta cost of keeping track of these blocks during each arithmetic
operation [and parallel partitioning of such variable blocks has its
own additional issues]

Satish