This commits contains the solver interface:
A = HYPREMatrix(...)
b = HYPREVector(...)
x = HYPREVector(...)
solver = HYPRESolver(; options...)
solve!(solver, x, A, b)
where the abstract type HYPRESolver is replaced by a concrete solver
implementation (this commit includes the concrete
implementation/wrapping of BoomerAMG <: HYPRESolver).
Solver settings are passed as keyword arguments to the solver
constructor, cf. SetXXX functions in HYPRE.
For example, to create a BoomerAMG solver, and setting the tolerance:
solver = BoomerAMG(Tol = 1e-7)
Keyword argument names correspond directly to the solvers SetXXX
function in HYPRE; passing Tol corresponds to
HYPRE_BoomerAMGSetTol(solver, 1e-7).