Ifpack2: multi-threaded Gauss-Seidel does not support damping

Created by: cgcgcg

@trilinos/ifpack2

Current Behavior

The multi-threaded version of Gauss-Seidel accepts a damping factor as parameter, just as the serial version. This value, however, is never used, so that the damping factor is effectively always 1.

Possible Solution

There are several options to deal with this issue:

• Change the underlying KokkosKernels implementation to allow damping.
• Display a warning when the damping factor != 1.
• Remove the damping factor parameter from the list of valid parameters.