hypre_obj_SetupSolIJver Subroutine

    impure subroutine hypre_obj_SetupSolIJver(this)
      !> Sets up solver with IJ interface.
      ! Note: for PCG/GMRES/BiCGSTAB, precond_id means:
      ! 1 - ds preconditioner
      ! 2 - amg preconditioner
      ! 3 - pilut preconditioner
      ! 4 - ParaSails preconditioner
      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)

        call HYPRE_BoomerAMGSetRelaxType    (this%solver, this%RelaxType,   ierr)
        call HYPRE_BoomerAMGSetRelaxOrder   (this%solver, 0,                ierr)
        call HYPRE_BoomerAMGSetCoarsenType  (this%solver, this%CoarsenType, ierr)
        call HYPRE_BoomerAMGSetKeepTransp   (this%solver, 1,                ierr)
#ifdef USE_GPU
        ! Parameters optimized for GPU
        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)
#else
        ! Parameters optimized for CPU
        call HYPRE_BoomerAMGSetInterpType   (this%solver, 6,                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_ParCSRPCGSetTwoNorm      (this%solver, 1,                ierr)
        call HYPRE_ParCSRPCGSetTol          (this%solver, this%MaxTol,      ierr)
        call HYPRE_ParCSRPCGSetMaxIter      (this%solver, this%MaxIt,       ierr)
        call HYPRE_ParCSRPCGSetPrintLevel   (this%solver, 2,                ierr)
        call HYPRE_ParCSRPCGSetLogging      (this%solver, 1,                ierr)

        ! Use BoomerAMG as preconditioner
        call HYPRE_BoomerAMGCreate          (this%precond,                  ierr)
        call HYPRE_BoomerAMGSetRelaxType    (this%solver, this%RelaxType,   ierr)
        call HYPRE_BoomerAMGSetCoarsenType  (this%solver, this%CoarsenType, ierr)
        call HYPRE_BoomerAMGSetInterpType   (this%precond, 6,               ierr)
        call HYPRE_BoomerAMGSetPrintLevel   (this%precond, 1,               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