krylov solver - atol Vs tol

[mbarbry]

Actually, we are using only the atol parameter for the krylov solvers and the tol parameter is left to its default value 1.0e-5.

However, the exit condition is defined as follow (in lgmres),

r_norm <= max(atol, tol * b_norm)

therefore, the condition on atol may not be satisfied, but the condition on tol with its default value maybe. We should define what kind of behavior we wish to have here