adding SNESSetLinearSolve()

[Richard Tran Mills]

Barry,

That accomplishes essentially the same thing as Lisandro's proposed 
SNESSetLinearSolve() but is more consistent with the existing framework of 
PETSc.  In fact, it seems *inconsistent* right now that there is a way to use 
a shell PC but not a way to use a shell KSP.  Since it is not always "natural" 
to think of every custom solver as a "preconditioner" (Lisandro provides an 
example), it seems like there ought to be a KSP shell option.  But what might 
this mess up?

Just my 0.5 cents.

--Richard

Barry Smith wrote:
> 
>    You seem to be saying you want something much like a KSP shell?