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
