precon.f90

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module precon
  use num_types, only : rp
  implicit none
  private
 
  type, public, abstract :: pc_t
   contains
     procedure(pc_solve), pass(this), deferred :: solve
     procedure(pc_update), pass(this), deferred :: update
  end type pc_t
 
  abstract interface
     subroutine pc_solve(this, z, r, n)
       import rp
       import :: pc_t
       implicit none
       integer, intent(in) :: n
       class(pc_t), intent(inout) :: this
       real(kind=rp), dimension(n), intent(inout) :: z
       real(kind=rp), dimension(n), intent(inout) :: r
     end subroutine pc_solve
     subroutine pc_update(this)
       import rp
       import :: pc_t
       implicit none
       class(pc_t), intent(inout) :: this
     end subroutine pc_update
  end interface
 
  interface
 
     module subroutine precon_allocator(pc, type_name)
       class(pc_t), allocatable, intent(inout) :: pc
       character(len=*), intent(in) :: type_name
     end subroutine precon_allocator
 
     module subroutine precon_destroy(pc)
       class(pc_t), allocatable, intent(inout) :: pc
     end subroutine precon_destroy
  end interface
 
  !
  ! Machinery for injecting user-defined types
  !
 
  abstract interface
     subroutine precon_allocate(obj)
       import pc_t
       class(pc_t), allocatable, intent(inout) :: obj
     end subroutine precon_allocate
  end interface
 
  interface
 
     module subroutine register_precon(type_name, allocator)
       character(len=*), intent(in) :: type_name
       procedure(precon_allocate), pointer, intent(in) :: allocator
     end subroutine register_precon
  end interface
 
  type precon_allocator_entry
     character(len=20) :: type_name
     procedure(precon_allocate), pointer, nopass :: allocator
  end type precon_allocator_entry
 
  type(precon_allocator_entry), allocatable :: precon_registry(:)
 
  integer :: precon_registry_size = 0
 
  public :: precon_allocator, precon_destroy, register_precon, precon_allocate
 
end module precon