writer_federator.F90

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module writer_federator_mod
  use datadefn_mod, only : default_precision, string_length
  use configuration_parser_mod, only : time_averaged_type, instantaneous_type, none_type, group_type, field_type, io_state_type, &
       io_configuration_type, io_configuration_field_type, io_configuration_diagnostic_field_type, &
       io_configuration_data_definition_type, data_values_type, get_data_value_by_field_name, get_diagnostic_field_configuration,&
       get_prognostic_field_configuration, get_monc_location
  use none_time_manipulation_mod, only : perform_none_time_manipulation, is_none_time_manipulation_ready_to_write
  use instantaneous_time_manipulation_mod, only : init_instantaneous_manipulation, finalise_instantaneous_manipulation, &
       perform_instantaneous_time_manipulation, is_instantaneous_time_manipulation_ready_to_write
  use timeaveraged_time_manipulation_mod, only : init_time_averaged_manipulation, finalise_time_averaged_manipulation, &
       perform_timeaveraged_time_manipulation, is_time_averaged_time_manipulation_ready_to_write
  use collections_mod, only : queue_type, list_type, map_type, hashmap_type, hashset_type, iterator_type, mapentry_type, &
       c_contains, c_size, c_get_string, c_get_generic, c_get_integer, c_add_string, c_free, c_put_real, c_put_generic, &
       c_key_at, c_is_empty, c_remove, c_push_generic, c_pop_generic, c_real_at, c_get_real, c_get_iterator, &
       c_has_next, c_next_mapentry, c_next_string, c_get_real, c_put_integer, c_add_generic
  use conversions_mod, only : conv_to_string, conv_single_real_to_double, conv_to_integer, conv_to_real
  use io_server_client_mod, only : array_field_type
  use forthread_mod, only : forthread_mutex_init, forthread_mutex_lock, forthread_mutex_unlock, forthread_mutex_destroy, &
       forthread_rwlock_rdlock, forthread_rwlock_wrlock, forthread_rwlock_unlock, forthread_rwlock_init, forthread_rwlock_destroy
  use threadpool_mod, only : check_thread_status
  use logging_mod, only : log_debug, log_error, log_warn, log_log, log_master_log, log_get_logging_level, log_is_master
  use writer_types_mod, only : writer_type, writer_field_type, write_field_collective_values_type, pending_write_type, &
       collective_q_field_representation_type, write_field_collective_descriptor_type, write_field_collective_monc_info_type
  use netcdf_filetype_writer_mod, only : initialise_netcdf_filetype, finalise_netcdf_filetype, define_netcdf_file, &
       write_variable, close_netcdf_file, store_io_server_state, get_writer_entry_from_netcdf
  use global_callback_inter_io_mod, only : perform_global_callback
  use data_utils_mod, only : get_scalar_integer_from_monc, get_scalar_real_from_monc, get_scalar_logical_from_monc, &
       is_field_present
  use io_server_client_mod, only : array_field_type, map_field_type, double_data_type, string_data_type
  use io_server_state_writer_mod, only : is_io_server_state_writer_ready
  use io_server_state_reader_mod, only : reactivate_writer_federator_state
  use grids_mod, only : z_index, y_index, x_index
  use mpi, only : mpi_int, mpi_max
  use mpi_communication_mod, only : lock_mpi, unlock_mpi
  implicit none

#ifndef TEST_MODE
  private
#endif

  type(writer_type), volatile, dimension(:), allocatable :: writer_entries
  type(hashset_type), volatile :: used_field_names, q_field_names
  type(hashmap_type), volatile :: time_points, q_field_splits, collective_q_field_dims

  integer, volatile :: time_points_rwlock, collective_contiguous_initialisation_mutex, currently_writing_mutex
  logical, volatile :: currently_writing

  public initialise_writer_federator, finalise_writer_federator, provide_ordered_field_to_writer_federator, &
       check_writer_for_trigger, issue_actual_write, is_field_used_by_writer_federator, inform_writer_federator_fields_present, &
       inform_writer_federator_time_point, provide_q_field_names_to_writer_federator, is_field_split_on_q
contains

  subroutine initialise_writer_federator(io_configuration, diagnostic_generation_frequency, continuation_run)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(hashmap_type), intent(inout) :: diagnostic_generation_frequency
    logical, intent(in) :: continuation_run

    integer :: i, j, number_contents, current_field_index
    type(hashset_type) :: writer_field_names, duplicate_field_names
    
    call check_thread_status(forthread_rwlock_init(time_points_rwlock, -1))
    call check_thread_status(forthread_mutex_init(collective_contiguous_initialisation_mutex, -1))
    call check_thread_status(forthread_mutex_init(currently_writing_mutex, -1))    

    currently_writing=.false.

    call init_time_averaged_manipulation()
    call init_instantaneous_manipulation()
    call initialise_netcdf_filetype()
    
    allocate(writer_entries(io_configuration%number_of_writers))    
    do i=1, io_configuration%number_of_writers
      current_field_index=0
      number_contents=io_configuration%file_writers(i)%number_of_contents
      allocate(writer_entries(i)%contents(get_total_number_writer_fields(io_configuration, i)))
      writer_entries(i)%filename=io_configuration%file_writers(i)%file_name
      writer_entries(i)%title=io_configuration%file_writers(i)%title
      writer_entries(i)%write_on_terminate=io_configuration%file_writers(i)%write_on_terminate
      writer_entries(i)%include_in_io_state_write=io_configuration%file_writers(i)%include_in_io_state_write
      call check_thread_status(forthread_mutex_init(writer_entries(i)%trigger_and_write_mutex, -1))
      call check_thread_status(forthread_mutex_init(writer_entries(i)%num_fields_to_write_mutex, -1))
      call check_thread_status(forthread_mutex_init(writer_entries(i)%pending_writes_mutex, -1))
      writer_entries(i)%write_on_model_time=io_configuration%file_writers(i)%write_on_model_time
      if (writer_entries(i)%write_on_model_time) then
        writer_entries(i)%write_timestep_frequency=0
        writer_entries(i)%write_time_frequency=io_configuration%file_writers(i)%write_time_frequency
      else
        writer_entries(i)%write_time_frequency=0
        writer_entries(i)%write_timestep_frequency=io_configuration%file_writers(i)%write_timestep_frequency
      end if
      writer_entries(i)%previous_write_time=0
      writer_entries(i)%defined_write_time=io_configuration%file_writers(i)%write_time_frequency
      writer_entries(i)%latest_pending_write_time=0
      writer_entries(i)%latest_pending_write_timestep=0      
      writer_entries(i)%contains_io_status_dump=.false.
      do j=1, number_contents
        if (io_configuration%file_writers(i)%contents(j)%facet_type == group_type) then
          current_field_index=add_group_of_fields_to_writer_entry(io_configuration, i, j, current_field_index, &
               writer_field_names, duplicate_field_names, diagnostic_generation_frequency)
        else if (io_configuration%file_writers(i)%contents(j)%facet_type == field_type) then
          current_field_index=current_field_index+add_field_to_writer_entry(io_configuration, &
           i, j, current_field_index, io_configuration%file_writers(i)%contents(j)%facet_name, "", writer_field_names, &
           duplicate_field_names, diagnostic_generation_frequency)
        else if (io_configuration%file_writers(i)%contents(j)%facet_type == io_state_type) then
          writer_entries(i)%contains_io_status_dump=.true.
        end if
      end do
      if (.not. c_is_empty(duplicate_field_names)) call handle_duplicate_field_names(writer_entries(i), duplicate_field_names)
      call c_free(writer_field_names)
      call c_free(duplicate_field_names)
    end do
    if (continuation_run) then
      call reactivate_writer_federator_state(io_configuration, writer_entries, time_points)
    end if    
  end subroutine initialise_writer_federator

  subroutine finalise_writer_federator()
    call check_thread_status(forthread_rwlock_destroy(time_points_rwlock))
    call check_thread_status(forthread_mutex_destroy(collective_contiguous_initialisation_mutex))
    call check_thread_status(forthread_mutex_destroy(currently_writing_mutex))    
    call finalise_time_averaged_manipulation()
    call finalise_instantaneous_manipulation()
    call finalise_netcdf_filetype()
  end subroutine finalise_writer_federator

  subroutine inform_writer_federator_time_point(io_configuration, source, data_id, data_dump)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: source, data_id
    character, dimension(:), allocatable, intent(in) :: data_dump

    real(kind=DEFAULT_PRECISION) :: time
    integer :: timestep
    character(len=STRING_LENGTH) :: timestep_key

    if (is_field_present(io_configuration, source, data_id, "time") .and. &
         is_field_present(io_configuration, source, data_id, "timestep")) then      
      time=get_scalar_real_from_monc(io_configuration, source, data_id, data_dump, "time")
      timestep=get_scalar_integer_from_monc(io_configuration, source, data_id, data_dump, "timestep")

      timestep_key=conv_to_string(timestep)

      call check_thread_status(forthread_rwlock_rdlock(time_points_rwlock))
      if (.not. c_contains(time_points, timestep_key)) then
        call check_thread_status(forthread_rwlock_unlock(time_points_rwlock))
        call check_thread_status(forthread_rwlock_wrlock(time_points_rwlock))
        if (.not. c_contains(time_points, timestep_key)) then
          call c_put_real(time_points, timestep_key, time)
        end if        
      end if
      call check_thread_status(forthread_rwlock_unlock(time_points_rwlock))      
    end if
  end subroutine inform_writer_federator_time_point

  subroutine inform_writer_federator_fields_present(io_configuration, field_names, diag_field_names_and_roots)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(hashset_type), intent(inout), optional :: field_names
    type(hashmap_type), intent(inout), optional :: diag_field_names_and_roots

    type(iterator_type) :: iterator
    character(len=STRING_LENGTH) :: specific_name
    integer :: i, number_q_fields, expected_io
    logical :: field_found, expected_here, diagnostics_mode

    iterator=c_get_iterator(used_field_names)
    expected_io=-1
    do while (c_has_next(iterator))
      specific_name=c_next_string(iterator)
      if (present(field_names)) then
        field_found=c_contains(field_names, specific_name)
        diagnostics_mode=.false.
      else if (present(diag_field_names_and_roots)) then
        field_found=c_contains(diag_field_names_and_roots, specific_name)
        if (field_found) expected_io=c_get_integer(diag_field_names_and_roots, specific_name)
        diagnostics_mode=.true.
      else
        field_found=.false.
      end if
      if (field_found) then
        expected_here=expected_io == -1 .or. expected_io == io_configuration%my_io_rank
        call enable_specific_field_by_name(specific_name, diagnostics_mode, expected_here)      
      end if
    end do
    iterator=c_get_iterator(q_field_names)
    do while (c_has_next(iterator))
      specific_name=c_next_string(iterator)
      if (present(field_names)) then
        field_found=c_contains(field_names, specific_name)
        diagnostics_mode=.false.
      else if (present(diag_field_names_and_roots)) then
        field_found=c_contains(diag_field_names_and_roots, specific_name)
        if (field_found) expected_io=c_get_integer(diag_field_names_and_roots, specific_name)
        diagnostics_mode=.true.
      else
        field_found=.false.
      end if
      if (field_found) then
        expected_here=expected_io == -1 .or. expected_io == io_configuration%my_io_rank
        number_q_fields=c_get_integer(io_configuration%dimension_sizing, "qfields")
        do i=1, number_q_fields
          if (c_size(io_configuration%q_field_names) .ge. i) then
            call enable_specific_field_by_name(trim(specific_name)//"_"//trim(c_get_string(io_configuration%q_field_names, i)), &
                 diagnostics_mode, expected_here)
          else
            call enable_specific_field_by_name(trim(specific_name)//"_udef"//trim(conv_to_string(i)), &
                 diagnostics_mode, expected_here)
          end if
        end do
      end if
    end do    
  end subroutine inform_writer_federator_fields_present  

  logical function is_field_used_by_writer_federator(field_name, field_namespace)
    character(len=*), intent(in) :: field_name, field_namespace

    integer :: writer_index, contents_index

    writer_index=1
    contents_index=1
    if (c_contains(used_field_names, field_name)) then      
      is_field_used_by_writer_federator=get_next_applicable_writer_entry(field_name, field_namespace, writer_index, contents_index)
    else
      is_field_used_by_writer_federator=.false.
    end if
  end function is_field_used_by_writer_federator

  logical function is_field_split_on_q(field_name)
    character(len=*), intent(in) :: field_name

    is_field_split_on_q=c_contains(q_field_names, field_name)
  end function is_field_split_on_q  

  subroutine enable_specific_field_by_name(field_name, diagnostics_mode, expected_here)
    character(len=*), intent(in) :: field_name
    logical, intent(in) :: diagnostics_mode
    logical, intent(in), optional :: expected_here

    logical :: continue_search
    integer :: writer_index, contents_index

    continue_search=.true.
    writer_index=1
    contents_index=0
    do while (continue_search)
      contents_index=contents_index+1
      continue_search=get_next_applicable_writer_entry(field_name, writer_index_point=writer_index, &
           contents_index_point=contents_index)
      if (continue_search) then
        if ((writer_entries(writer_index)%contents(contents_index)%diagnostic_field .and. diagnostics_mode) .or. &
             (writer_entries(writer_index)%contents(contents_index)%prognostic_field .and. .not. diagnostics_mode)) then
          writer_entries(writer_index)%contents(contents_index)%enabled=.true.
          if (present(expected_here)) then
            writer_entries(writer_index)%contents(contents_index)%expected_here=expected_here
          end if
        end if
      end if      
    end do    
  end subroutine enable_specific_field_by_name

  subroutine provide_q_field_names_to_writer_federator(q_provided_field_names)
    type(list_type), intent(inout) :: q_provided_field_names

    type(iterator_type) :: iterator, q_field_iterator
    logical :: continue_search
    integer :: writer_index, contents_index, i
    character(len=STRING_LENGTH) :: search_field, field_name, specific_name

    iterator=c_get_iterator(q_field_names)
    do while (c_has_next(iterator))
      specific_name=c_next_string(iterator)
      q_field_iterator=c_get_iterator(q_provided_field_names)
      i=1
      do while (c_has_next(q_field_iterator))
        search_field=trim(specific_name)//"_udef"//trim(conv_to_string(i))
        field_name=trim(specific_name)//"_"//trim(c_next_string(q_field_iterator))        
        continue_search=.true.
        writer_index=1
        contents_index=0
        do while (continue_search)
          contents_index=contents_index+1
          continue_search=get_next_applicable_writer_entry(search_field, writer_index_point=writer_index, &
               contents_index_point=contents_index)
          if (continue_search) then
            writer_entries(writer_index)%contents(contents_index)%field_name=field_name
          end if
        end do
        i=i+1
        call c_add_string(used_field_names, field_name)
        call c_remove(used_field_names, search_field)
      end do     
    end do    
  end subroutine provide_q_field_names_to_writer_federator

  subroutine provide_ordered_field_to_writer_federator(io_configuration, field_name, field_namespace, field_values, &
       timestep, time, source)
    type(io_configuration_type), intent(inout) :: io_configuration
    character(len=*), intent(in) :: field_name, field_namespace
    integer, intent(in) :: timestep, source
    type(data_values_type), target :: field_values
    real(kind=DEFAULT_PRECISION), intent(in) :: time

    integer :: writer_index, contents_index
    logical :: continue_search
    type(data_values_type), pointer :: result_values
    type(hashmap_type) :: typed_result_values
    class(*), pointer :: generic

    if (field_values%data_type == double_data_type) then
      call provide_ordered_field_to_writer_federator_real_values(io_configuration, field_name, field_namespace, &
           field_values%values, timestep, time, source)
    else if (field_values%data_type == string_data_type) then
      continue_search=.true.
      writer_index=1
      contents_index=0
      allocate(result_values, source=field_values)
      generic=>result_values
      if (c_contains(used_field_names, field_name)) then
        do while (continue_search)
          contents_index=contents_index+1
          continue_search=get_next_applicable_writer_entry(field_name, field_namespace, writer_index, contents_index)
          if (continue_search) then
            if (.not. writer_entries(writer_index)%contents(contents_index)%enabled) then
              call log_log(log_warn, "Received data for previously un-enabled field '"//&
                   writer_entries(writer_index)%contents(contents_index)%field_name//"'")
            end if
            writer_entries(writer_index)%contents(contents_index)%enabled=.true.          
            writer_entries(writer_index)%contents(contents_index)%latest_timestep_values=timestep
            if (log_get_logging_level() .ge. log_debug) then
              call log_log(log_debug, "[WRITE FED VALUE STORE] Storing value for field "//trim(field_name)//" ts="//&
                   trim(conv_to_string(timestep))// " t="//trim(conv_to_string(time)))
            end if
            call check_thread_status(forthread_mutex_lock(writer_entries(writer_index)%contents(contents_index)%values_mutex))           
            call c_put_generic(writer_entries(writer_index)%contents(contents_index)%values_to_write, conv_to_string(time), &
                 generic, .false.)
            call check_thread_status(forthread_mutex_unlock(writer_entries(writer_index)%contents(contents_index)%values_mutex))
            if (writer_entries(writer_index)%contents(contents_index)%pending_to_write) then
              call determine_if_outstanding_field_can_be_written(io_configuration, writer_entries(writer_index), &
                   writer_entries(writer_index)%contents(contents_index))
            end if
          end if
        end do
      end if
    end if
  end subroutine provide_ordered_field_to_writer_federator  

  subroutine provide_ordered_field_to_writer_federator_real_values(io_configuration, field_name, field_namespace, field_values, &
       timestep, time, source)
    type(io_configuration_type), intent(inout) :: io_configuration
    character(len=*), intent(in) :: field_name, field_namespace
    integer, intent(in) :: timestep, source
    real(kind=DEFAULT_PRECISION), dimension(:), intent(in) :: field_values
    real(kind=DEFAULT_PRECISION), intent(in) :: time

    type(iterator_type) :: iterator
    integer :: individual_size, index
    
    if (c_contains(used_field_names, field_name)) then
      call provide_ordered_single_field_to_writer_federator(io_configuration, field_name, field_namespace, field_values, &
           timestep, time, source)
    else if (c_contains(q_field_names, field_name)) then
      if (c_contains(q_field_splits, field_name)) then
        individual_size=c_get_integer(q_field_splits, field_name)
      else if (source .gt. -1) then
        individual_size=get_size_of_collective_q(io_configuration, field_name, source)
      else
        call log_log(log_warn, "Can not find Q split field in Q field names or collective field names with source, ignoring")
        return
      end if
      iterator=c_get_iterator(io_configuration%q_field_names)
      index=1
      do while (c_has_next(iterator))
        call provide_ordered_single_field_to_writer_federator(io_configuration, &
             trim(field_name)//"_"//trim(c_next_string(iterator)), field_namespace, field_values(index:index+individual_size-1), &
             timestep, time, source)
        index=index+individual_size
      end do
    end if
  end subroutine provide_ordered_field_to_writer_federator_real_values

  integer function get_size_of_collective_q(io_configuration, field_name, source)
    type(io_configuration_type), intent(inout) :: io_configuration
    character(len=*), intent(in) :: field_name
    integer, intent(in) :: source

    class(*), pointer :: generic
    integer :: i, monc_index

    get_size_of_collective_q=1
    monc_index=get_monc_location(io_configuration, source)
    generic=>c_get_generic(collective_q_field_dims, field_name)
    select type(generic)
      type is(collective_q_field_representation_type)
        do i=1, size(generic%dimensions)
          get_size_of_collective_q=&
               get_size_of_collective_q*io_configuration%registered_moncs(monc_index)%local_dim_sizes(generic%dimensions(i))
        end do        
    end select    
  end function get_size_of_collective_q  

  subroutine provide_ordered_single_field_to_writer_federator(io_configuration, field_name, field_namespace, field_values, &
       timestep, time, source)
    type(io_configuration_type), intent(inout) :: io_configuration
    character(len=*), intent(in) :: field_name, field_namespace
    integer, intent(in) :: timestep, source
    real(kind=DEFAULT_PRECISION), dimension(:), intent(in) :: field_values
    real(kind=DEFAULT_PRECISION), intent(in) :: time

    integer :: writer_index, contents_index
    logical :: continue_search
    type(data_values_type), pointer :: result_values
    type(hashmap_type) :: typed_result_values
    class(*), pointer :: generic

    continue_search=.true.
    writer_index=1
    contents_index=0
    if (c_contains(used_field_names, field_name)) then
      do while (continue_search)
        contents_index=contents_index+1
        continue_search=get_next_applicable_writer_entry(field_name, field_namespace, writer_index, contents_index)
        if (continue_search) then
          if (.not. writer_entries(writer_index)%contents(contents_index)%enabled) then
            call log_log(log_warn, "Received data for previously un-enabled field '"//&
                 writer_entries(writer_index)%contents(contents_index)%field_name//"'")
          end if          
          writer_entries(writer_index)%contents(contents_index)%enabled=.true.
          if (.not. c_contains(typed_result_values, conv_to_string(&
               writer_entries(writer_index)%contents(contents_index)%time_manipulation_type))) then
            allocate(result_values)
            if (writer_entries(writer_index)%contents(contents_index)%collective_write .and. source .gt. -1) then
              result_values=writer_entries(writer_index)%contents(contents_index)%time_manipulation(field_values, &
                   writer_entries(writer_index)%contents(contents_index)%output_frequency, &
                   trim(field_name)//"#"//conv_to_string(source), timestep, time)
            else
              result_values=writer_entries(writer_index)%contents(contents_index)%time_manipulation(field_values, &
                   writer_entries(writer_index)%contents(contents_index)%output_frequency, &
                   field_name, timestep, time)
            end if
            generic=>result_values
            call c_put_generic(typed_result_values, conv_to_string(&
                 writer_entries(writer_index)%contents(contents_index)%time_manipulation_type), generic, .false.)
          else
            result_values=>get_data_value_by_field_name(typed_result_values, conv_to_string(&
                 writer_entries(writer_index)%contents(contents_index)%time_manipulation_type))            
          end if
          if (allocated(result_values%values)) then
            writer_entries(writer_index)%contents(contents_index)%latest_timestep_values=timestep
            if (log_get_logging_level() .ge. log_debug) then
              call log_log(log_debug, "[WRITE FED VALUE STORE] Storing value for field "//trim(field_name)//" ts="//&
                   trim(conv_to_string(timestep))// " t="//trim(conv_to_string(time)))
            end if
            call check_thread_status(forthread_mutex_lock(writer_entries(writer_index)%contents(contents_index)%values_mutex))
            if (writer_entries(writer_index)%contents(contents_index)%collective_write .and.  source .gt. -1) then
              call write_collective_write_value(result_values, writer_index, contents_index, source, conv_to_string(time))
            else
              call c_put_generic(writer_entries(writer_index)%contents(contents_index)%values_to_write, conv_to_string(time), &
                   generic, .false.)
            end if
            call check_thread_status(forthread_mutex_unlock(writer_entries(writer_index)%contents(contents_index)%values_mutex))
            if (writer_entries(writer_index)%contents(contents_index)%pending_to_write) then
              call determine_if_outstanding_field_can_be_written(io_configuration, writer_entries(writer_index), &
                   writer_entries(writer_index)%contents(contents_index))
            end if                        
          end if
        end if
      end do
    end if
    call c_free(typed_result_values)
  end subroutine provide_ordered_single_field_to_writer_federator

  subroutine write_collective_write_value(result_values, writer_index, contents_index, source, lookup_key)
    integer, intent(in) :: writer_index, contents_index, source
    type(data_values_type), pointer :: result_values
    character(len=*), intent(in) :: lookup_key

    class(*), pointer :: generic
    type(write_field_collective_values_type), pointer :: stored_monc_values

    if (c_contains(writer_entries(writer_index)%contents(contents_index)%values_to_write, lookup_key)) then
      generic=>c_get_generic(writer_entries(writer_index)%contents(contents_index)%values_to_write, lookup_key)
      select type(generic)
        type is(write_field_collective_values_type)
          stored_monc_values=>generic
      end select      
    else
      allocate(stored_monc_values)
      generic=>stored_monc_values
      call c_put_generic(writer_entries(writer_index)%contents(contents_index)%values_to_write, lookup_key, generic, .false.)
    end if
    generic=>result_values
    call c_put_generic(stored_monc_values%monc_values, conv_to_string(source), generic, .false.)
  end subroutine write_collective_write_value  

  subroutine determine_if_outstanding_field_can_be_written(io_configuration, writer_entry, specific_field)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_type), intent(inout) :: writer_entry
    type(writer_field_type), intent(inout) :: specific_field

    logical :: field_write_success, do_close_num_fields

    if (specific_field%pending_to_write) then    
      call determine_if_field_can_be_written(io_configuration, writer_entry, specific_field, writer_entry%write_timestep, &
           writer_entry%previous_write_timestep, writer_entry%write_time, writer_entry%previous_write_time, field_write_success)
      if (field_write_success) then
        if (log_get_logging_level() .ge. log_debug) then
          call log_log(log_debug, "Flushed outstanding field ts="//conv_to_string(writer_entry%write_timestep)//&
               " write time="//conv_to_string(writer_entry%write_time))
        end if
        call check_thread_status(forthread_mutex_lock(writer_entry%num_fields_to_write_mutex))
        writer_entry%num_fields_to_write=writer_entry%num_fields_to_write-1
        do_close_num_fields=writer_entry%num_fields_to_write == 0
        call check_thread_status(forthread_mutex_unlock(writer_entry%num_fields_to_write_mutex))
        if (do_close_num_fields) then
          call close_diagnostics_file(io_configuration, writer_entry, writer_entry%write_timestep, writer_entry%write_time)
        end if    
      end if
    end if
  end subroutine determine_if_outstanding_field_can_be_written  

  subroutine determine_if_field_can_be_written(io_configuration, writer_entry, specific_field, &
       timestep, previous_write_timestep, write_time, previous_write_time, field_written)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_type), intent(inout) :: writer_entry
    type(writer_field_type), intent(inout) :: specific_field
    integer, intent(in) :: timestep, previous_write_timestep
    real, intent(in) :: write_time, previous_write_time
    logical, intent(out), optional :: field_written

    real :: value_to_test, largest_value_found
    integer :: num_matching
    type(iterator_type) :: iterator
    type(mapentry_type) :: map_entry
    type(write_field_collective_values_type), pointer :: multi_monc_entries
    class(*), pointer :: generic
        
    num_matching=0
    largest_value_found=0.0
    call check_thread_status(forthread_mutex_lock(specific_field%values_mutex))
    if (.not. c_is_empty(specific_field%values_to_write)) then
      iterator=c_get_iterator(specific_field%values_to_write)
      do while (c_has_next(iterator))
        map_entry=c_next_mapentry(iterator)
        value_to_test=conv_to_real(map_entry%key)
        if (specific_field%collective_write) then
          generic=>c_get_generic(map_entry)
          select type(generic)
          type is(write_field_collective_values_type)
            multi_monc_entries=>generic
          end select
          if (c_size(multi_monc_entries%monc_values) .ne. io_configuration%number_of_moncs) cycle
        end if
        if (value_to_test .le. write_time .and. value_to_test .gt. previous_write_time) then        
          num_matching=num_matching+1
          if (largest_value_found .lt. value_to_test) largest_value_found=value_to_test
        end if
      end do
    end if

    if (num_matching .gt. 0 .and. specific_field%ready_to_write(largest_value_found, specific_field%output_frequency, write_time, &
         specific_field%latest_timestep_values, timestep)) then
      if (.not. specific_field%collective_write .or. .not. specific_field%collective_contiguous_optimisation) then
        if (specific_field%issue_write) then
          call write_variable(io_configuration, specific_field, writer_entry%filename, timestep, write_time)
        end if
        specific_field%previous_write_time=writer_entry%write_time
      end if      
      specific_field%pending_to_write=.false.
      if (present(field_written)) field_written=.true.
    else
      if (log_get_logging_level() .ge. log_debug) then
          call log_log(log_debug, "Setting outstanding field ts="//conv_to_string(writer_entry%write_timestep)//&
               " write time="//conv_to_string(writer_entry%write_time)//" prev="//conv_to_string(previous_write_time)//&
               " largest entry="//conv_to_string(largest_value_found)//" num matching="//conv_to_string(num_matching))
        end if
      specific_field%pending_to_write=.true.
      if (present(field_written)) field_written=.false.
    end if
    call check_thread_status(forthread_mutex_unlock(specific_field%values_mutex))
  end subroutine determine_if_field_can_be_written

  subroutine check_writer_for_trigger(io_configuration, source, data_id, data_dump)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: source, data_id
    character, dimension(:), allocatable, intent(in) :: data_dump

    integer :: i, timestep
    real(kind=DEFAULT_PRECISION) :: time
    logical :: terminated

    if (is_field_present(io_configuration, source, data_id, "timestep") .and. &
         is_field_present(io_configuration, source, data_id, "time")) then
      timestep=get_scalar_integer_from_monc(io_configuration, source, data_id, data_dump, "timestep")
      time=get_scalar_real_from_monc(io_configuration, source, data_id, data_dump, "time")

      if (is_field_present(io_configuration, source, data_id, "terminated")) then
        terminated=get_scalar_logical_from_monc(io_configuration, source, data_id, data_dump, "terminated")
      else
        terminated=.false.
      end if
      do i=1, size(writer_entries)
        call check_writer_trigger(io_configuration, i, timestep, real(time, kind=4), terminated)
      end do
    end if
  end subroutine check_writer_for_trigger

  subroutine check_writer_trigger(io_configuration, writer_entry_index, timestep, time, terminated)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: writer_entry_index, timestep
    real, intent(in) :: time
    logical, intent(in) :: terminated

    real :: time_difference
    integer :: i
    logical :: issue_write, issue_terminated_write
    
    call check_thread_status(forthread_mutex_lock(writer_entries(writer_entry_index)%trigger_and_write_mutex))
    issue_terminated_write=writer_entries(writer_entry_index)%write_on_terminate .and. terminated
    if (writer_entries(writer_entry_index)%write_on_model_time) then
      time_difference=time-writer_entries(writer_entry_index)%latest_pending_write_time
      issue_write=time_difference .ge. writer_entries(writer_entry_index)%write_time_frequency      
    else
      if (writer_entries(writer_entry_index)%write_timestep_frequency .gt. 0) then
        issue_write=writer_entries(writer_entry_index)%latest_pending_write_timestep .ne. timestep .and. &
             mod(timestep, writer_entries(writer_entry_index)%write_timestep_frequency) == 0
      else
        issue_write=.false.
      end if
      issue_terminated_write=issue_terminated_write .and. &
           writer_entries(writer_entry_index)%latest_pending_write_timestep .ne. timestep
    end if

    if (issue_write .or. issue_terminated_write) then
      writer_entries(writer_entry_index)%latest_pending_write_time=time
      writer_entries(writer_entry_index)%latest_pending_write_timestep=timestep

      call check_thread_status(forthread_mutex_lock(currently_writing_mutex))    

      if (currently_writing) then
        call check_thread_status(forthread_mutex_unlock(currently_writing_mutex))
        call check_thread_status(forthread_mutex_unlock(writer_entries(writer_entry_index)%trigger_and_write_mutex))
        call register_pending_file_write(writer_entry_index, timestep, time, &
             writer_entries(writer_entry_index)%write_on_terminate .and. terminated)
      else
        currently_writing=.true.
        call check_thread_status(forthread_mutex_unlock(currently_writing_mutex))
        call check_thread_status(forthread_mutex_unlock(writer_entries(writer_entry_index)%trigger_and_write_mutex))
        call issue_actual_write(io_configuration, writer_entries(writer_entry_index), timestep, time, &
             writer_entries(writer_entry_index)%write_on_terminate .and. terminated)
      end if
    else
      call check_thread_status(forthread_mutex_unlock(writer_entries(writer_entry_index)%trigger_and_write_mutex))
    end if
  end subroutine check_writer_trigger

  subroutine issue_actual_write(io_configuration, writer_entry, timestep, time, terminated_write)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_type), intent(inout) :: writer_entry
    integer, intent(in) :: timestep
    real, intent(in) :: time
    logical, intent(in) :: terminated_write

    integer :: i, j, total_outstanding, num_written, total_flds
    logical :: field_written
    type(map_type) :: applicable_time_points

    call check_thread_status(forthread_mutex_lock(collective_contiguous_initialisation_mutex))
    do i=1, size(writer_entry%contents)
      if (writer_entry%contents(i)%enabled .and. writer_entry%contents(i)%collective_write) then
        if (.not. writer_entry%contents(i)%collective_initialised) then
          call determine_collective_type_and_optimise_if_possible(io_configuration, writer_entry%contents(i))
        end if
      end if
    end do
    call check_thread_status(forthread_mutex_unlock(collective_contiguous_initialisation_mutex))
    
    writer_entry%write_time=time
    writer_entry%write_timestep=timestep
    applicable_time_points=extract_applicable_time_points(writer_entry%previous_write_time, time)    
    call define_netcdf_file(io_configuration, writer_entry, timestep, time, applicable_time_points, terminated_write)
    call c_free(applicable_time_points)
    total_outstanding=0
    total_flds=0
    num_written=0
    call check_thread_status(forthread_mutex_lock(writer_entry%num_fields_to_write_mutex))
    do j=1, size(writer_entry%contents)  
      if (writer_entry%contents(j)%enabled .and. writer_entry%contents(j)%expected_here) then
        total_flds=total_flds+1
        call determine_if_field_can_be_written(io_configuration, writer_entry, writer_entry%contents(j), timestep, &
             writer_entry%previous_write_timestep, time, writer_entry%contents(j)%previous_write_time, field_written)
        if (.not. field_written) then          
          total_outstanding=total_outstanding+1
        else
          num_written=num_written+1
        end if
      end if
    end do
    writer_entry%num_fields_to_write=total_outstanding
    call check_thread_status(forthread_mutex_unlock(writer_entry%num_fields_to_write_mutex))
    if (log_get_logging_level() .ge. log_debug) then
      call log_log(log_debug, "Started write for NetCDF file, timestep= "//trim(conv_to_string(timestep))&
           //" total="//trim(conv_to_string(total_flds))//" written="//trim(conv_to_string(num_written))//&
           " outstanding="//trim(conv_to_string(total_outstanding)))
    end if
    if (total_outstanding == 0) then
      call close_diagnostics_file(io_configuration, writer_entry, timestep, time)
    end if    
  end subroutine issue_actual_write

  type(map_type) function extract_applicable_time_points(start_time, end_time)
    real, intent(in) :: start_time, end_time

    real :: time_entry
    type(iterator_type) :: iterator
    type(mapentry_type) :: map_entry

    call check_thread_status(forthread_rwlock_rdlock(time_points_rwlock))
    iterator=c_get_iterator(time_points)
    do while (c_has_next(iterator))
      map_entry=c_next_mapentry(iterator)
      time_entry=real(c_get_real(map_entry))
      if (time_entry .gt. start_time .and. time_entry .le. end_time) then
        call c_put_real(extract_applicable_time_points, map_entry%key, conv_single_real_to_double(time_entry))
      end if
    end do
    call check_thread_status(forthread_rwlock_unlock(time_points_rwlock))
    extract_applicable_time_points=sort_applicable_time_points(extract_applicable_time_points)
  end function extract_applicable_time_points

  type(map_type) function sort_applicable_time_points(unsorted_timepoints)
    type(map_type), intent(inout) :: unsorted_timepoints

    integer :: i, entries, specific_ts, smallest_ts
    character(len=STRING_LENGTH) :: smallest_key
    real(kind=DEFAULT_PRECISION) :: rvalue
    type(iterator_type) :: iterator
    type(mapentry_type) :: map_entry

    entries=c_size(unsorted_timepoints)
    do i=1, entries
      smallest_key=""
      iterator=c_get_iterator(unsorted_timepoints)
      do while (c_has_next(iterator))
        map_entry=c_next_mapentry(iterator)
        specific_ts=conv_to_integer(map_entry%key)
        if (len_trim(smallest_key) == 0 .or. smallest_ts .gt. specific_ts) then
          smallest_ts=specific_ts
          smallest_key=map_entry%key
          rvalue=c_get_real(map_entry)
        end if        
      end do
      call c_put_real(sort_applicable_time_points, smallest_key, rvalue)
      call c_remove(unsorted_timepoints, smallest_key)
    end do
    call c_free(unsorted_timepoints)
  end function sort_applicable_time_points  

  subroutine close_diagnostics_file(io_configuration, writer_entry, timestep, time)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_type), intent(inout) :: writer_entry
    integer, intent(in) :: timestep
    real, intent(in) :: time

    if (log_get_logging_level() .ge. log_debug) then
      call log_log(log_debug, "Issue close for NetCDF file at timestep "//trim(conv_to_string(timestep)))
    end if
    call perform_global_callback(io_configuration, writer_entry%filename, timestep, handle_close_diagnostics_globalcallback)
  end subroutine close_diagnostics_file

  subroutine handle_close_diagnostics_globalcallback(io_configuration, values, field_name, timestep)
    type(io_configuration_type), intent(inout) :: io_configuration
    real(DEFAULT_PRECISION), dimension(:) :: values
    character(len=STRING_LENGTH) :: field_name
    integer :: timestep
    
    type(writer_type), pointer :: writer_entry
    integer :: i
    logical :: terminated, done_chain_run

    writer_entry=>get_writer_entry_from_netcdf(field_name, timestep, terminated)    

    do i=1, size(writer_entry%contents)
      if (writer_entry%contents(i)%enabled .and. writer_entry%contents(i)%collective_write .and. &
           writer_entry%contents(i)%collective_contiguous_optimisation) then        
        call check_thread_status(forthread_mutex_lock(writer_entry%contents(i)%values_mutex))
        call write_variable(io_configuration, writer_entry%contents(i), writer_entry%filename, timestep, writer_entry%write_time)
        writer_entry%contents(i)%previous_write_time=writer_entry%write_time
        call check_thread_status(forthread_mutex_unlock(writer_entry%contents(i)%values_mutex))
      end if      
    end do

    writer_entry%previous_write_time=writer_entry%write_time
    writer_entry%previous_write_timestep=writer_entry%write_timestep
    writer_entry%defined_write_time=writer_entry%defined_write_time+writer_entry%write_time_frequency

    if (writer_entry%contains_io_status_dump) then
      if (.not. terminated) then
        do while (.not. is_io_server_state_writer_ready(timestep))
        end do
      end if
      call check_thread_status(forthread_rwlock_rdlock(time_points_rwlock))
      call store_io_server_state(io_configuration, writer_entries, time_points, writer_entry, timestep)
      call check_thread_status(forthread_rwlock_unlock(time_points_rwlock))
    end if

    call close_netcdf_file(io_configuration, field_name, timestep)

    done_chain_run=.false.
    do i=1, size(writer_entries)
      if (writer_entries(i)%filename .ne. writer_entry%filename) then
        done_chain_run=check_for_and_issue_chain_write(io_configuration, writer_entries(i))
        if (done_chain_run) exit
      end if
    end do
    if (.not. done_chain_run) done_chain_run=check_for_and_issue_chain_write(io_configuration, writer_entry)

    if (.not. done_chain_run) then
      call check_thread_status(forthread_mutex_lock(currently_writing_mutex))
      currently_writing=.false.
      call check_thread_status(forthread_mutex_unlock(currently_writing_mutex))
      if (log_get_logging_level() .ge. log_debug) then
        call log_log(log_debug, "No more pending entries to chain to at ts= "//trim(conv_to_string(timestep)))
      end if
    end if
  end subroutine handle_close_diagnostics_globalcallback

  logical function check_for_and_issue_chain_write(io_configuration, writer_entry)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_type), intent(inout) :: writer_entry

    class(*), pointer :: generic

    call check_thread_status(forthread_mutex_lock(writer_entry%pending_writes_mutex))
    if (.not. c_is_empty(writer_entry%pending_writes)) then
      check_for_and_issue_chain_write=.true.
      generic=>c_pop_generic(writer_entry%pending_writes)    
      call check_thread_status(forthread_mutex_unlock(writer_entry%pending_writes_mutex))
      select type(generic)
      type is (pending_write_type)
        if (log_get_logging_level() .ge. log_debug) then
          call log_log(log_debug, "Chain to next pending entry ts= "//trim(conv_to_string(generic%timestep)))
        end if
        call issue_actual_write(io_configuration, writer_entry, generic%timestep, &
             generic%write_time, generic%terminated_write)
        deallocate(generic)
      end select
    else
      check_for_and_issue_chain_write=.false.
      call check_thread_status(forthread_mutex_unlock(writer_entry%pending_writes_mutex))
    end if    
  end function check_for_and_issue_chain_write
  
  subroutine register_pending_file_write(writer_entry_index, timestep, time, terminated_write)
    integer, intent(in) :: writer_entry_index, timestep
    real, intent(in) :: time
    logical, intent(in) :: terminated_write

    type(pending_write_type), pointer :: pending_write
    class(*), pointer :: generic

    allocate(pending_write)
    pending_write%write_time=time
    pending_write%timestep=timestep
    pending_write%terminated_write=terminated_write

    generic=>pending_write
    call check_thread_status(forthread_mutex_lock(writer_entries(writer_entry_index)%pending_writes_mutex))
    call c_push_generic(writer_entries(writer_entry_index)%pending_writes, generic, .false.)
    call check_thread_status(forthread_mutex_unlock(writer_entries(writer_entry_index)%pending_writes_mutex))
  end subroutine register_pending_file_write  

  logical function get_next_applicable_writer_entry(field_name, field_namespace, writer_index_point, contents_index_point)
    character(len=*), intent(in) :: field_name
    character(len=*), intent(in), optional :: field_namespace
    integer, intent(inout) :: writer_index_point, contents_index_point

    integer :: i, j

    if (writer_index_point .le. size(writer_entries)) then    
      do i=writer_index_point, size(writer_entries)
        if (contents_index_point .le. size(writer_entries(i)%contents)) then
          do j=contents_index_point, size(writer_entries(i)%contents)           
            if (writer_entries(i)%contents(j)%field_name==field_name) then
              if (present(field_namespace)) then                
                if (writer_entries(i)%contents(j)%field_namespace .ne. field_namespace) cycle
              end if
              writer_index_point=i
              contents_index_point=j
              get_next_applicable_writer_entry=.true.
              return
            end if
          end do
        end if
        contents_index_point=1
      end do
    end if
    get_next_applicable_writer_entry=.false.
  end function get_next_applicable_writer_entry  

  integer function get_total_number_writer_fields(io_configuration, writer_entry_index)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: writer_entry_index

    integer :: i, number_contents, group_index, number_q_fields

    get_total_number_writer_fields=0
    number_q_fields=c_get_integer(io_configuration%dimension_sizing, "qfields")

    number_contents=io_configuration%file_writers(writer_entry_index)%number_of_contents
    do i=1, number_contents
      if (io_configuration%file_writers(writer_entry_index)%contents(i)%facet_type == group_type) then          
        group_index=get_index_of_group(io_configuration, &
             io_configuration%file_writers(writer_entry_index)%contents(i)%facet_name)
        if (group_index == 0) call log_log(log_error, "Can not find group '"//trim(&
             io_configuration%file_writers(writer_entry_index)%contents(i)%facet_name)//"'")
        get_total_number_writer_fields=get_total_number_writer_fields+&
             get_group_number_of_fields(io_configuration, io_configuration%groups(group_index)%members, number_q_fields, &
             io_configuration%groups(group_index)%namespace)
      else if (io_configuration%file_writers(writer_entry_index)%contents(i)%facet_type == field_type) then
        ! NSE
        get_total_number_writer_fields=get_total_number_writer_fields+get_field_number_of_fields(io_configuration, &
             io_configuration%file_writers(writer_entry_index)%contents(i)%facet_name, "", number_q_fields)
      end if
    end do
  end function get_total_number_writer_fields

  integer function get_group_number_of_fields(io_configuration, group_members, num_q_fields, namespace)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(list_type) :: group_members
    integer, intent(in) :: num_q_fields
    character(len=STRING_LENGTH), intent(in) :: namespace

    type(iterator_type) :: iterator
    character(len=STRING_LENGTH) :: field_name
    
    get_group_number_of_fields=0
    iterator=c_get_iterator(group_members)
    do while (c_has_next(iterator))
      field_name=c_next_string(iterator)
      get_group_number_of_fields=get_group_number_of_fields+get_field_number_of_fields(io_configuration, field_name, namespace, &
           num_q_fields)
    end do
  end function get_group_number_of_fields

  integer function get_field_number_of_fields(io_configuration, field_name, field_namespace, num_q_fields)
    type(io_configuration_type), intent(inout) :: io_configuration
    character(len=STRING_LENGTH), intent(in) :: field_name, field_namespace
    integer, intent(in) :: num_q_fields

    type(io_configuration_field_type) :: prognostic_field_configuration
    type(io_configuration_data_definition_type) :: prognostic_containing_data_defn
    type(io_configuration_diagnostic_field_type) :: diagnostic_field_configuration
    
    if (get_diagnostic_field_configuration(io_configuration, field_name, field_namespace, diagnostic_field_configuration)) then
      if (diagnostic_field_configuration%field_type == array_field_type) then
        if (diagnostic_field_configuration%dim_size_defns(diagnostic_field_configuration%dimensions) .eq. "qfields") then
          get_field_number_of_fields=num_q_fields
          return
        end if
      end if
      get_field_number_of_fields=1
    else if (get_prognostic_field_configuration(io_configuration, field_name, field_namespace, &
         prognostic_field_configuration, prognostic_containing_data_defn)) then
      if (prognostic_field_configuration%field_type == array_field_type) then
        if (prognostic_field_configuration%dim_size_defns(prognostic_field_configuration%dimensions) .eq. "qfields") then
          get_field_number_of_fields=num_q_fields
          return
        end if
      end if
        get_field_number_of_fields=1
    end if
  end function get_field_number_of_fields

  integer function add_group_of_fields_to_writer_entry(io_configuration, writer_entry_index, facet_index, current_field_index, &
       writer_field_names, duplicate_field_names, diagnostic_generation_frequency)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: writer_entry_index, facet_index, current_field_index
    type(hashset_type), intent(inout) :: writer_field_names, duplicate_field_names
    type(hashmap_type), intent(inout) :: diagnostic_generation_frequency

    integer :: group_index
    character(len=STRING_LENGTH) :: field_name
    type(iterator_type) :: iterator

    add_group_of_fields_to_writer_entry=current_field_index
    group_index=get_index_of_group(io_configuration, &
         io_configuration%file_writers(writer_entry_index)%contents(facet_index)%facet_name)
    if (group_index == 0) then
      call log_log(log_error, "Can not find group '"//&
           trim(io_configuration%file_writers(writer_entry_index)%contents(facet_index)%facet_name)//"' in the configuration")
    end if
    iterator=c_get_iterator(io_configuration%groups(group_index)%members)
    do while (c_has_next(iterator))
      field_name=c_next_string(iterator)
      add_group_of_fields_to_writer_entry=add_group_of_fields_to_writer_entry+add_field_to_writer_entry(io_configuration, &
           writer_entry_index, facet_index, add_group_of_fields_to_writer_entry, field_name, &
           io_configuration%groups(group_index)%namespace, writer_field_names, duplicate_field_names, &
           diagnostic_generation_frequency)
    end do    
  end function add_group_of_fields_to_writer_entry

  integer function add_field_to_writer_entry(io_configuration, writer_entry_index, io_config_facet_index, &
       my_facet_index, field_name, field_namespace, writer_field_names, duplicate_field_names, diagnostic_generation_frequency)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: writer_entry_index, io_config_facet_index, my_facet_index
    character(len=*), intent(in) :: field_name, field_namespace
    type(hashset_type), intent(inout) :: writer_field_names, duplicate_field_names
    type(hashmap_type), intent(inout) :: diagnostic_generation_frequency

    integer :: i, number_q_fields, tot_size
    type(io_configuration_field_type) :: prognostic_field_configuration
    type(io_configuration_data_definition_type) :: prognostic_containing_data_defn
    type(io_configuration_diagnostic_field_type) :: diagnostic_field_configuration
    type(collective_q_field_representation_type), pointer :: collective_q_field
    class(*), pointer :: generic
    
    if (get_diagnostic_field_configuration(io_configuration, field_name, field_namespace, diagnostic_field_configuration)) then
      if (diagnostic_field_configuration%field_type == array_field_type) then
        if (diagnostic_field_configuration%dim_size_defns(diagnostic_field_configuration%dimensions) .eq. "qfields") then  
          number_q_fields=c_get_integer(io_configuration%dimension_sizing, "qfields")
          do i=1, number_q_fields
            call add_specific_field_to_writer_entry(io_configuration, writer_entry_index, io_config_facet_index, &
                 my_facet_index+i, trim(field_name)//"_udef"//trim(conv_to_string(i)), field_namespace, writer_field_names, &
                 duplicate_field_names, c_get_integer(diagnostic_generation_frequency, field_name), diagnostic_field_configuration)
          end do
          tot_size=1
          do i=1, writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dimensions
            tot_size=tot_size*writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%actual_dim_size(i)
          end do
          call c_put_integer(q_field_splits, field_name, tot_size)
          add_field_to_writer_entry=number_q_fields
          return
        end if
      end if
      call add_specific_field_to_writer_entry(io_configuration, writer_entry_index, io_config_facet_index, &
           my_facet_index+1, field_name, field_namespace, writer_field_names, duplicate_field_names, &
           c_get_integer(diagnostic_generation_frequency, field_name), diagnostic_field_configuration)
      add_field_to_writer_entry=1      
    else if (get_prognostic_field_configuration(io_configuration, field_name, field_namespace, &
         prognostic_field_configuration, prognostic_containing_data_defn)) then
      if (prognostic_field_configuration%field_type == array_field_type) then
        if (prognostic_field_configuration%dim_size_defns(prognostic_field_configuration%dimensions) .eq. "qfields") then  
          number_q_fields=c_get_integer(io_configuration%dimension_sizing, "qfields")
          do i=1, number_q_fields
            call add_specific_field_to_writer_entry(io_configuration, writer_entry_index, io_config_facet_index, &
                 my_facet_index+i, trim(field_name)//"_udef"//trim(conv_to_string(i)), field_namespace, writer_field_names, &
                 duplicate_field_names, prognostic_containing_data_defn%frequency, &
                 prognostic_field_configuration=prognostic_field_configuration)
          end do
          if (prognostic_field_configuration%collective) then
            allocate(collective_q_field)
            allocate(collective_q_field%dimensions(&
                 writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dimensions))
            do i=1, writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dimensions
              if (trim(writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dim_size_defns(i)) == "z") then
                collective_q_field%dimensions(i)=1
              else if (trim(writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dim_size_defns(i)) &
                   == "y") then
                collective_q_field%dimensions(i)=2
              else if (trim(writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dim_size_defns(i)) &
                   == "x") then
                collective_q_field%dimensions(i)=3
              end if
            end do
            generic=>collective_q_field
            call c_put_generic(collective_q_field_dims, field_name, generic, .false.)
          else
            tot_size=1
            do i=1, writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%dimensions
              tot_size=tot_size*writer_entries(writer_entry_index)%contents(my_facet_index+number_q_fields)%actual_dim_size(i)
            end do
            call c_put_integer(q_field_splits, field_name, tot_size)
          end if
          call c_add_string(q_field_names, field_name)
          add_field_to_writer_entry=number_q_fields
          return
        end if     
      end if
      call add_specific_field_to_writer_entry(io_configuration, writer_entry_index, io_config_facet_index, &
           my_facet_index+1, field_name, field_namespace, writer_field_names, duplicate_field_names, &
           prognostic_containing_data_defn%frequency, prognostic_field_configuration=prognostic_field_configuration)
      add_field_to_writer_entry=1
    else
      call log_log(log_error, "Field '"//trim(field_name)//&
           "' configured for file write but can not find this as a prognostic or diagnostic definition")
    end if
  end function add_field_to_writer_entry  

  subroutine add_specific_field_to_writer_entry(io_configuration, writer_entry_index, io_config_facet_index, &
       my_facet_index, field_name, field_namespace, writer_field_names, duplicate_field_names, timestep_frequency, &
       diagnostic_field_configuration, prognostic_field_configuration)
    type(io_configuration_type), intent(inout) :: io_configuration
    integer, intent(in) :: writer_entry_index, io_config_facet_index, my_facet_index, timestep_frequency
    character(len=*), intent(in) :: field_name, field_namespace
    type(hashset_type), intent(inout) :: writer_field_names, duplicate_field_names
    type(io_configuration_diagnostic_field_type), intent(inout), optional :: diagnostic_field_configuration
    type(io_configuration_field_type), intent(inout), optional :: prognostic_field_configuration
    
    integer :: i

    writer_entries(writer_entry_index)%contents(my_facet_index)%field_name=field_name
    writer_entries(writer_entry_index)%contents(my_facet_index)%field_namespace=field_namespace

    call c_add_string(used_field_names, field_name)
    
    if (.not. c_contains(writer_field_names, field_name)) then
      call c_add_string(writer_field_names, writer_entries(writer_entry_index)%contents(my_facet_index)%field_name)
    else
      call c_add_string(duplicate_field_names, writer_entries(writer_entry_index)%contents(my_facet_index)%field_name)
    end if

    if (io_configuration%file_writers(writer_entry_index)%contents(io_config_facet_index)%time_manipulation_type == &
         instantaneous_type) then
      writer_entries(writer_entry_index)%contents(my_facet_index)%time_manipulation=>perform_instantaneous_time_manipulation
      writer_entries(writer_entry_index)%contents(my_facet_index)%ready_to_write=>is_instantaneous_time_manipulation_ready_to_write
    else if (io_configuration%file_writers(writer_entry_index)%contents(io_config_facet_index)%time_manipulation_type == &
         time_averaged_type) then        
      writer_entries(writer_entry_index)%contents(my_facet_index)%time_manipulation=>perform_timeaveraged_time_manipulation
      writer_entries(writer_entry_index)%contents(my_facet_index)%ready_to_write=>is_time_averaged_time_manipulation_ready_to_write
    else if (io_configuration%file_writers(writer_entry_index)%contents(io_config_facet_index)%time_manipulation_type == &
         none_type) then        
      writer_entries(writer_entry_index)%contents(my_facet_index)%time_manipulation=>perform_none_time_manipulation
      writer_entries(writer_entry_index)%contents(my_facet_index)%ready_to_write=>is_none_time_manipulation_ready_to_write
    end if
    writer_entries(writer_entry_index)%contents(my_facet_index)%time_manipulation_type=&
         io_configuration%file_writers(writer_entry_index)%contents(io_config_facet_index)%time_manipulation_type
    writer_entries(writer_entry_index)%contents(my_facet_index)%output_frequency=&
         io_configuration%file_writers(writer_entry_index)%contents(io_config_facet_index)%output_time_frequency
    writer_entries(writer_entry_index)%contents(my_facet_index)%previous_write_time=0.0
    writer_entries(writer_entry_index)%contents(my_facet_index)%previous_tracked_write_point=0.0   
    writer_entries(writer_entry_index)%contents(my_facet_index)%duplicate_field_name=.false.
    writer_entries(writer_entry_index)%contents(my_facet_index)%pending_to_write=.false.
    writer_entries(writer_entry_index)%contents(my_facet_index)%enabled=.false.
    writer_entries(writer_entry_index)%contents(my_facet_index)%expected_here=.true.
    writer_entries(writer_entry_index)%contents(my_facet_index)%prognostic_field=.false.
    writer_entries(writer_entry_index)%contents(my_facet_index)%diagnostic_field=.false.

    if (present(diagnostic_field_configuration)) then
      writer_entries(writer_entry_index)%contents(my_facet_index)%timestep_frequency=timestep_frequency
      writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions=diagnostic_field_configuration%dimensions
      writer_entries(writer_entry_index)%contents(my_facet_index)%data_type=diagnostic_field_configuration%data_type
      writer_entries(writer_entry_index)%contents(my_facet_index)%field_type=diagnostic_field_configuration%field_type
      writer_entries(writer_entry_index)%contents(my_facet_index)%dim_size_defns=diagnostic_field_configuration%dim_size_defns
      writer_entries(writer_entry_index)%contents(my_facet_index)%units=diagnostic_field_configuration%units
      writer_entries(writer_entry_index)%contents(my_facet_index)%collective_write=diagnostic_field_configuration%collective
      writer_entries(writer_entry_index)%contents(my_facet_index)%collective_initialised=.false.
      writer_entries(writer_entry_index)%contents(my_facet_index)%issue_write=.true.
      writer_entries(writer_entry_index)%contents(my_facet_index)%diagnostic_field=.true.
    else if (present(prognostic_field_configuration)) then
      writer_entries(writer_entry_index)%contents(my_facet_index)%timestep_frequency=timestep_frequency
      writer_entries(writer_entry_index)%contents(my_facet_index)%data_type=prognostic_field_configuration%data_type
      writer_entries(writer_entry_index)%contents(my_facet_index)%field_type=prognostic_field_configuration%field_type
      writer_entries(writer_entry_index)%contents(my_facet_index)%units=prognostic_field_configuration%units
      writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions=prognostic_field_configuration%dimensions
      writer_entries(writer_entry_index)%contents(my_facet_index)%collective_write=prognostic_field_configuration%collective
      writer_entries(writer_entry_index)%contents(my_facet_index)%collective_initialised=.false.
      writer_entries(writer_entry_index)%contents(my_facet_index)%prognostic_field=.true.
      if (.not. prognostic_field_configuration%collective) then
        writer_entries(writer_entry_index)%contents(my_facet_index)%issue_write=io_configuration%my_io_rank==0
      else
        writer_entries(writer_entry_index)%contents(my_facet_index)%issue_write=.true.
      end if      
      if (prognostic_field_configuration%field_type == array_field_type .or. &
           prognostic_field_configuration%field_type == map_field_type) then
        if (prognostic_field_configuration%dimensions .gt. 0) then
          writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions=prognostic_field_configuration%dimensions
          writer_entries(writer_entry_index)%contents(my_facet_index)%dim_size_defns=&
               prognostic_field_configuration%dim_size_defns
        else
          call log_log(log_error, "The writing prognostic field '"//trim(field_name)//"' configuration must have dimensions")
        end if
      end if
    else
      call log_log(log_error, "A diagnostic or prognostic configuration for the field '"//trim(field_name)//"' was not found")
    end if
    if (writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions .gt. 0) then
      if (writer_entries(writer_entry_index)%contents(my_facet_index)%dim_size_defns(&
           writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions) .eq. "qfields") then
        writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions=&
             writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions-1
      end if      
      do i=1, writer_entries(writer_entry_index)%contents(my_facet_index)%dimensions
        writer_entries(writer_entry_index)%contents(my_facet_index)%actual_dim_size(i)=c_get_integer(&
             io_configuration%dimension_sizing, writer_entries(writer_entry_index)%contents(my_facet_index)%dim_size_defns(i))
      end do      
    end if    
    call check_thread_status(forthread_mutex_init(writer_entries(writer_entry_index)%contents(my_facet_index)%values_mutex, -1))
  end subroutine add_specific_field_to_writer_entry

  subroutine handle_duplicate_field_names(writer_entry, duplicate_field_names)
    type(writer_type), intent(inout) :: writer_entry
    type(hashset_type), intent(inout) :: duplicate_field_names

    integer :: i

    do i=1, size(writer_entry%contents)
      if (c_contains(duplicate_field_names, writer_entry%contents(i)%field_name)) then
        writer_entry%contents(i)%duplicate_field_name=.true.
      end if      
    end do    
  end subroutine handle_duplicate_field_names  

  integer function get_index_of_group(io_configuration, group_name)
    type(io_configuration_type), intent(inout) :: io_configuration
    character(len=*), intent(in) :: group_name

    integer :: i, entries

    entries=io_configuration%number_of_groups
    do i=1, entries
      if (io_configuration%groups(i)%name == group_name) then
        get_index_of_group=i
        return
      end if
    end do
    get_index_of_group=0
  end function get_index_of_group

  subroutine determine_collective_type_and_optimise_if_possible(io_configuration, field_to_write_information)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_field_type), intent(inout) :: field_to_write_information

    if (field_to_write_information%dimensions .eq. 3 .and. &
         get_dimension_identifier(field_to_write_information%dim_size_defns(1)) == z_index .and. &
         get_dimension_identifier(field_to_write_information%dim_size_defns(2)) == y_index .and. &
         get_dimension_identifier(field_to_write_information%dim_size_defns(3)) == x_index) then
      field_to_write_information%collective_contiguous_optimisation=.true.
      call initialise_contiguous_data_regions(io_configuration, field_to_write_information)
    else
      field_to_write_information%collective_contiguous_optimisation=.false.
    end if
    field_to_write_information%collective_initialised=.true.
  end subroutine determine_collective_type_and_optimise_if_possible  

  subroutine initialise_contiguous_data_regions(io_configuration, field_to_write_information)
    type(io_configuration_type), intent(inout) :: io_configuration
    type(writer_field_type), intent(inout) :: field_to_write_information

    integer :: start(field_to_write_information%dimensions, io_configuration%number_of_moncs), &
         count(field_to_write_information%dimensions, io_configuration%number_of_moncs), &
         common_starters(io_configuration%number_of_moncs), num_common, num_current_contents, active_dim, other_dim, &
         j, k, i, dim_identifier, number_distinct_writes, start_blocks(io_configuration%number_of_moncs), ierr, &
         count_blocks(io_configuration%number_of_moncs), current_contents(io_configuration%number_of_moncs), &
         monc_write_start_offset_per_dim(field_to_write_information%dimensions,io_configuration%number_of_moncs)
    logical :: processed(io_configuration%number_of_moncs)

    type(write_field_collective_descriptor_type), pointer :: collective_descriptor
    type(write_field_collective_monc_info_type), pointer :: specific_monc_collective
    class(*), pointer :: generic  

    processed=.false.
    number_distinct_writes=0
    do j=1, io_configuration%number_of_moncs
      do k=1, field_to_write_information%dimensions
        dim_identifier=get_dimension_identifier(field_to_write_information%dim_size_defns(k))
        start(k, j)=io_configuration%registered_moncs(j)%local_dim_starts(dim_identifier)
        count(k, j)=io_configuration%registered_moncs(j)%local_dim_sizes(dim_identifier)
      end do
    end do

    do j=1, io_configuration%number_of_moncs
      if (.not. processed(j)) then
        call get_common_starts(y_index, start(y_index, j), start, common_starters, num_common)
        if (num_common == 0) then
          call get_common_starts(x_index, start(x_index, j), start, common_starters, num_common)
          if (num_common .gt. 0) then
            active_dim=x_index
            other_dim=y_index
          end if
        else
          active_dim=y_index
          other_dim=x_index
        end if
          number_distinct_writes=number_distinct_writes+1
          allocate(collective_descriptor)
          allocate(collective_descriptor%absolute_start(field_to_write_information%dimensions), &
               collective_descriptor%count(field_to_write_information%dimensions))
          start_blocks(number_distinct_writes)=start(other_dim, j)
          count_blocks(number_distinct_writes)=count(other_dim, j)
          num_current_contents=1
          current_contents(num_current_contents)=j
          processed(j)=.true.
          if (num_common .gt. 0) then
            do k=1, num_common
              do i=1, num_common
                if (.not. processed(common_starters(i)) .and. count(active_dim, j) == count(active_dim, i)) then
                  if (start(other_dim, common_starters(i)) .lt. start_blocks(number_distinct_writes) .and. &
                       start(other_dim, common_starters(i)) + count(other_dim, common_starters(i)) &
                       == start_blocks(number_distinct_writes)) then
                    start_blocks(number_distinct_writes)=start(other_dim, common_starters(i))
                    count_blocks(number_distinct_writes)=count_blocks(number_distinct_writes)+count(other_dim, common_starters(i))
                    processed(common_starters(i))=.true.                    
                    num_current_contents=num_current_contents+1
                    current_contents(num_current_contents)=common_starters(i)
                  else if (start(other_dim, common_starters(i)) .gt. start_blocks(number_distinct_writes) .and. &
                       start_blocks(number_distinct_writes) + count_blocks(number_distinct_writes) &
                       == start(other_dim, common_starters(i))) then
                    count_blocks(number_distinct_writes)=count_blocks(number_distinct_writes)+count(other_dim, common_starters(i))
                    processed(common_starters(i))=.true.                    
                    num_current_contents=num_current_contents+1
                    current_contents(num_current_contents)=common_starters(i)
                  end if
                end if
              end do
            end do
          end if
          collective_descriptor%absolute_start=start(:,j)
          collective_descriptor%count=count(:,j)
          collective_descriptor%absolute_start(other_dim)=start_blocks(number_distinct_writes)
          collective_descriptor%count(other_dim)=count_blocks(number_distinct_writes)
          collective_descriptor%split_dim=other_dim
          if (num_current_contents .gt. 0) then
            do k=1, num_current_contents
              allocate(specific_monc_collective)                          
              specific_monc_collective%relative_dimension_start=(start(other_dim,current_contents(k))-&
                   start_blocks(number_distinct_writes)) + 1              
              specific_monc_collective%counts=count(:, current_contents(k))
              specific_monc_collective%monc_location=current_contents(k)
              specific_monc_collective%monc_source=io_configuration%registered_moncs(current_contents(k))%source_id
              generic=>specific_monc_collective
              call c_add_generic(collective_descriptor%specific_monc_info, generic, .false.)
            end do
          end if
          generic=>collective_descriptor
          call c_add_generic(field_to_write_information%collective_descriptors, generic, .false.)
      end if
    end do
    call lock_mpi()
    call mpi_iallreduce(number_distinct_writes, field_to_write_information%max_num_collective_writes, 1, mpi_int, mpi_max, &
         io_configuration%io_communicator, field_to_write_information%max_num_collective_writes_request_handle, ierr)
    call unlock_mpi()
  end subroutine initialise_contiguous_data_regions

  subroutine get_common_starts(dim, val, vals, common_starters, num_common)
    integer, intent(in) :: dim, val
    integer, dimension(:,:), intent(in) :: vals
    integer, dimension(:), intent(out) :: common_starters
    integer, intent(out) :: num_common

    integer :: i

    num_common=0
    do i=1, size(vals, 2)
      if (vals(dim, i) == val) then
        num_common=num_common+1
        common_starters(num_common)=i
      end if      
    end do    
  end subroutine get_common_starts

  integer function get_dimension_identifier(dim_name, is_auto_dimension)
    character(len=*), intent(in) :: dim_name
    logical, intent(out), optional :: is_auto_dimension

    integer :: dash_idx
    logical :: is_modified_size

    dash_idx=index(dim_name, "_")
    dash_idx=dash_idx-1
    is_modified_size=dash_idx .ne. -1
    if (.not. is_modified_size) dash_idx=len_trim(dim_name)

    if (dim_name(:dash_idx) .eq. "z" .or. dim_name(:dash_idx) .eq. "zn") then
      get_dimension_identifier=z_index
    else if (dim_name(:dash_idx) .eq. "y") then
      get_dimension_identifier=y_index
    else if (dim_name(:dash_idx) .eq. "x") then
      get_dimension_identifier=x_index
    else
      get_dimension_identifier=-1
    end if

    if (present(is_auto_dimension)) is_auto_dimension=is_modified_size
  end function get_dimension_identifier
end module writer_federator_mod