hypre_obj_SetupSolIJver Subroutine

    impure subroutine hypre_obj_SetupSolIJver(this)
      !> Sets up solver with IJ interface.
      implicit none
      class(hypre_obj), intent(inout) :: this                                  !! Hypre machinery
      ! Work variables
      integer :: ierr
      integer :: precond_id

      select case (this%solver_name)
      case (HYPRE_SOL_IJ_AMG_NONE)
        ! Using Boomer AMG (no preconditioning)
        call HYPRE_BoomerAMGCreate           (this%solver,             ierr)
        call HYPRE_BoomerAMGSetPrintLevel    (this%solver, 0,          ierr)

#ifdef USE_GPU
        ! Parameters optimized for GPU
        call HYPRE_BoomerAMGSetRelaxType    (this%solver, 11,          ierr)
        call HYPRE_BoomerAMGSetRelaxOrder   (this%solver, 0,           ierr)
        call HYPRE_BoomerAMGSetCoarsenType  (this%solver, 8,           ierr)
        call HYPRE_BoomerAMGSetInterpType   (this%solver, 14,          ierr)
        call HYPRE_BoomerAMGSetAggNumLevels (this%solver, 0,           ierr)
        call HYPRE_BoomerAMGSetAggInterpType(this%solver, 5,           ierr)
        call HYPRE_BoomerAMGSetRAP2         (this%solver, 0,           ierr)
        call HYPRE_BoomerAMGSetKeepTransp   (this%solver, 1,           ierr)
#else
        call HYPRE_BoomerAMGSetCoarsenType  (this%solver, 10,          ierr)
        call HYPRE_BoomerAMGSetInterpType   (this%solver, 6,           ierr)
        call HYPRE_BoomerAMGSetRelaxType    (this%solver, 8,           ierr)
        call HYPRE_BoomerAMGSetRelaxOrder   (this%solver, 0,           ierr)
        call HYPRE_BoomerAMGSetKeepTransp   (this%solver, 1,           ierr)
        call HYPRE_BoomerAMGSetPMaxElmts    (this%solver, 4,           ierr)
#endif
        call HYPRE_BoomerAMGSetNumSweeps    (this%solver, 1,           ierr)
        call HYPRE_BoomerAMGSetMaxLevels    (this%solver, 25,          ierr)
        call HYPRE_BoomerAMGSetMaxIter      (this%solver, this%MaxIt,  ierr)
        call HYPRE_BoomerAMGSetTol          (this%solver, this%MaxTol, ierr)

        call HYPRE_BoomerAMGSetup(this%solver, this%par_matrix, this%par_rhs, this%par_sol, ierr)
      case (HYPRE_SOL_IJ_PCG_AMG)
        ! Using PCG with AMG preconditioning
        call HYPRE_ParCSRPCGCreate          (this%comm,   this%solver, ierr)
        call HYPRE_ParCSRPCGSetTol          (this%solver, this%MaxTol, ierr)
        call HYPRE_ParCSRPCGSetMaxIter      (this%solver, this%MaxIt,  ierr)
        call HYPRE_ParCSRPCGSetTwoNorm      (this%solver, 1,           ierr)
        call HYPRE_ParCSRPCGSetLogging      (this%solver, 1,           ierr)

        call HYPRE_BoomerAMGCreate          (this%precond,             ierr)
        call HYPRE_BoomerAMGSetPrintLevel   (this%precond, 1,          ierr)
        call HYPRE_BoomerAMGSetCoarsenType  (this%precond, 8,          ierr)
        call HYPRE_BoomerAMGSetInterpType   (this%precond, 3,          ierr)
        call HYPRE_BoomerAMGSetRelaxType    (this%precond, 6,          ierr)
        call HYPRE_BoomerAMGSetNumSweeps    (this%precond, 1,          ierr)
        call HYPRE_BoomerAMGSetMaxIter      (this%precond, 1,          ierr)
        call HYPRE_BoomerAMGSetTol          (this%precond, 0.0_wp,     ierr)

        precond_id=2
        call HYPRE_ParCSRPCGSetPrecond(this%solver, precond_id, this%precond, ierr)

        call HYPRE_ParCSRPCGSetup(this%solver, this%par_matrix, this%par_rhs, this%par_sol, ierr)
      case (HYPRE_SOL_IJ_PCG_DS)
        ! Using PCG with DS preconditioning
        call HYPRE_ParCSRPCGCreate           (this%comm,   this%solver,ierr)
        call HYPRE_ParCSRPCGSetTol           (this%solver, this%MaxTol,ierr)
        call HYPRE_ParCSRPCGSetMaxIter       (this%solver, this%MaxIt, ierr)
        call HYPRE_ParCSRPCGSetTwoNorm       (this%solver, 1,          ierr)
        !call HYPRE_ParCSRPCGSetPrintLevel(this%solver, 2, ierr)
        call HYPRE_ParCSRPCGSetLogging       (this%solver, 1,          ierr)

        precond_id=1
        call HYPRE_ParCSRPCGSetPrecond(this%solver, precond_id, this%precond, ierr)

        call HYPRE_ParCSRPCGSetup(this%solver, this%par_matrix, this%par_rhs, this%par_sol, ierr)
      case default
        call this%parallel%Stop("Unknown HYPRE solver")
      end select

      return
    end subroutine hypre_obj_SetupSolIJver