krylov.f90

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module krylov
  use gather_scatter, only : gs_t, gs_op_add
  use ax_product, only : ax_t
  use num_types, only: rp, c_rp
  use precon,  only : pc_t
  use coefs, only : coef_t
  use mesh, only : mesh_t
  use field, only : field_t
  use utils, only : neko_error, neko_warning
  use bc, only : bc_list_t
  use identity, only : ident_t
  use device_identity, only : device_ident_t
  use neko_config
  implicit none
  private
 
  integer, public, parameter :: ksp_max_iter = 1e4       
  real(kind=rp), public, parameter :: ksp_abs_tol = 1d-9 
  real(kind=rp), public, parameter :: ksp_rel_tol = 1d-9 
 
  type, public :: ksp_monitor_t
     integer :: iter
     real(kind=rp) :: res_start
     real(kind=rp) :: res_final
  end type ksp_monitor_t
 
  type, public, abstract :: ksp_t
     class(pc_t), pointer :: m => null() 
     real(kind=rp) :: rel_tol            
     real(kind=rp) :: abs_tol            
     integer :: max_iter
     class(pc_t), allocatable :: m_ident
   contains
     procedure, pass(this) :: ksp_init => krylov_init
     procedure, pass(this) :: ksp_free => krylov_free
     procedure, pass(this) :: set_pc => krylov_set_pc
     procedure(ksp_method), pass(this), deferred :: solve
     procedure(ksp_t_free), pass(this), deferred :: free
  end type ksp_t
 
 
  abstract interface
     function ksp_method(this, Ax, x, f, n, coef, blst, gs_h, niter) result(ksp_results)
       import :: bc_list_t
       import :: field_t
       import :: ksp_t
       import :: coef_t
       import :: gs_t
       import :: ax_t
       import :: ksp_monitor_t
       import rp
       implicit none
       class(ksp_t), intent(inout) :: this
       class(ax_t), intent(inout) :: ax
       type(field_t), intent(inout) :: x
       integer, intent(in) :: n
       real(kind=rp), dimension(n), intent(inout) :: f
       type(coef_t), intent(inout) :: coef
       type(bc_list_t), intent(inout) :: blst
       type(gs_t), intent(inout) :: gs_h
       integer, optional, intent(in) :: niter
       type(ksp_monitor_t) :: ksp_results
     end function ksp_method
  end interface
 
  abstract interface
     subroutine ksp_t_free(this)
       import :: ksp_t
       class(ksp_t), intent(inout) :: this
     end subroutine ksp_t_free
  end interface
 
contains
 
  subroutine krylov_init(this, max_iter, rel_tol, abs_tol, M)
    class(ksp_t), target, intent(inout) :: this
    integer, intent(in) :: max_iter
    real(kind=rp), optional, intent(in) :: rel_tol
    real(kind=rp), optional, intent(in) :: abs_tol
    class(pc_t), optional, target, intent(in) :: m
 
    call krylov_free(this)
 
    if (present(rel_tol)) then
       this%rel_tol = rel_tol
    else
       this%rel_tol = ksp_rel_tol
    end if
 
    if (present(abs_tol)) then
       this%abs_tol = abs_tol
    else
       this%abs_tol = ksp_abs_tol
    end if
 
    this%max_iter = max_iter
 
    if (present(m)) then
       this%M => m
    else
       if (.not. associated(this%M)) then
          if (neko_bcknd_device .eq. 1) then
             allocate(device_ident_t::this%M_ident)
          else
             allocate(ident_t::this%M_ident)
          end if
          this%M => this%M_ident
       end if
    end if
 
  end subroutine krylov_init
 
  subroutine krylov_free(this)
    class(ksp_t), intent(inout) :: this
 
 
  end subroutine krylov_free
 
  subroutine krylov_set_pc(this, M)
    class(ksp_t), intent(inout) :: this
    class(pc_t), target, intent(in) :: M
 
    if (associated(this%M)) then
       select type(pc => this%M)
       type is (ident_t)
       type is (device_ident_t)
       class default
          call neko_error('Preconditioner already defined')
       end select
    end if
 
    this%M => m
 
  end subroutine krylov_set_pc
 
end module krylov