[petsc-dev] Non-scalable matrix operations

[Jed Brown]

On Fri, Dec 23, 2011 at 13:11, Mark F. Adams <mark.adams at columbia.edu>wrote:
>
> Sure, but what does the user need to provide? How much code can we reuse
> between the matrix-based implementation and the nonlinear implementation?
>
>
> You just have to provide a method like
>
> int applyGS( Mat mat, Vec lhs, Vec rhs, IS eqs, Bool reverse)
>
> that applies G-S to the local rows in "eqs" and processes them in reverse
> order if "reverse" is true.  Reverse is just to symmetrize the operator.
>  Since this is probably best used for non-symetric operators we could
> simplify the algorithm a bit and get rid of this ...
>

Sure, so this update lhs for some equations, but there is no Mat (because
it's nonlinear). To create the ISs, we'll have to specify the connections
between nodes (could use a matrix to denote that).
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