There is no concept of sparsity in vectors in PETSc.
If much of your Vec is zero entries then it is expected that you define
subproblems that work with only the relevant part of the vectors in your
algorithms and not expect it to come "for free" from the usual PETSc operations.
Barry
On Feb 9, 2012, at 8:09 AM, Hui Zhang wrote:
> Hi,
>
> Is sparsity of Vec exploited in MatMult? I'm implementing some domain
> decomposition
> methods. The residual is non-zero or significant only at very few nodes. Does
> MatMult knows that most entries of the Vec are zeros? Is there a threshold to
> regard an value as zero?
>
> Thanks,
> Hui
