[petsc-dev] sor smoothers

[Mark F. Adams]

On Sep 8, 2013, at 9:11 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> "Mark F. Adams" <mfadams at lbl.gov> writes:
> 
>> So I should add a residual method to Mat, get rid of PCMGResidualDefault, make a MatResidualDefault, and have SetUp_MatAIJ set this default.
>> 
>> I guess PCMGSetResidual would just set the residual for Mat to keep
>> the same interface or should we just get rid of it and make a
>> MatSetResidual?
> 
> PCMGSetResidual (if we continue to support it) should not modify the Mat

I don't see how we can support this if we want to use MatResidual as Barry has described.  Certainly without adding a lot more ugly to the code.  

> because we can't let its effects escape the solve.  That is, we should
> be able to create two solvers and not have the presence of the first
> affect the algorithm used when we pass the matrix on to the second.
> 
> Note that there is MatShellSetOperation.