Sets the vector to be used to store the residual on a particular level.
PetscErrorCode PCMGSetR(PC pc,PetscInt l,Vec c)
Logically Collective on PC
|pc ||- the multigrid context
|l ||- the level (0 is coarsest) this is to be used for
|c ||- the Vec
If this is not provided PETSc will automatically generate one. You do not need to keep a reference to this vector if you do not need it. PCDestroy() will properly free it.
MG, multigrid, set, residual, level