Re: Task Discriminants & Arrays

["John G. Volan" <johnvolan@sprintmail.com>]

Robert A Duff wrote:

> I suppose
> you could have an array of tasks, and an array of pointers to tasks, and
> sort the latter (and hide the former from clients).  The only advantage
> I can see to that is that it allows parallel activation of the tasks.

An interesting suggestion. We could have something like:

  task type Process_Type
    (Process_Id : Process_Id_Type := Get_New_Process_Id)
     -- Note: We have to make sure this function is already
     -- elaborated at this point; probably needs to be in another
     -- package
  is
    ...
  end Process_Type;

  type Process_Access_Type is access all Process_Type;

  type Process_Array_Type is
    array (Process_Index_Type range <>) of aliased Process_Type;
    -- Note: Process_Index_Type does not necessarily have to be
    -- the same as Process_Id_Type.  In fact, they probably should
    -- be different to avoid confusing the id of a process with its
    -- arbitrary location in such an array, which won't necessarily
    -- be the same.

  type Process_Access_Array_Type is
    array (Process_Id_Type range <>) of Process_Access_Type;

  procedure Find_Process_Id_Bounds
    (Process_Array      : in     Process_Array_Type;
     Minimum_Process_Id :    out Process_Id_Type;
     Maximum_Process_Id :    out Process_Id_Type)
  is
    ...
  begin
    ... -- left as an exercise for the reader
  end Find_Process_Id_Bounds;

  function Get_Process_Access_Array
    (Process_Array : access Process_Array_Type)
     return Process_Access_Array_Type
  is
    Minimum_Process_Id, Maximum_Process_Id : Process_Id_Type;
  begin
    Find_Process_Id_Bounds
      (Process_Array.all, Minimum_Process_Id, Maximum_Process_Id);
    declare
      Process_Access_Array : Process_Access_Array_Type
        (Minimum_Process_Id .. Maximum_Process_Id);
    begin
      for Process_Index in Process_Array'Range loop
        declare
          Process : constant Process_Access_Type :=
            Process_Array(Process_Index)'Access;
        begin
          Process_Access_Array(Process.Process_Id) := Process;
        end;
      end loop;
      return Process_Access_Array;
    end;
  end Get_Process_Access_Array;

And then in the client application code:

  package Jeff_Carters_Million_Processes is

    Process_Array : aliased Process_Array_Type (1 .. 1E6);
    -- Wham!! ... all activated at once

    Process_Access_Array : constant Process_Access_Array_Type :=
      Get_Process_Access_Array (Process_Array'Access);

    -- Deciding whether and how to hide either or both of these
    -- arrays is left as an exercise for the reader.

  end Jeff_Carters_Million_Processes;

:-) :-) :-)


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