[petsc-dev] ML via --download-ml

[Garth N. Wells]

I've noticed very different performance with ML when I (a) link PETSc
to a Trilinos installation; or (b) use --download-ml. I observe

- Case (a): solver behaves exactly as I would expect. Iteration counts
very close to GAMG iteration counts, minimal dependency on problem
size.

- Case (b): iteration counts higher and substantial increase in
iteration count with problem size.

I haven't debugged since I usually link to Trilinos, in which case
performance is as I expect.

Garth