------------------------------------------------------------------------------
------------------------------------------------------------------------------
-- Cheddar is a GNU GPL real-time scheduling analysis tool.
-- This program provides services to automatically check schedulability and
-- other performance criteria of real-time architecture models.
--
-- Copyright (C) 2002-2020, Frank Singhoff, Alain Plantec, Jerome Legrand,
--                          Hai Nam Tran, Stephane Rubini
--
-- The Cheddar project was started in 2002 by
-- Frank Singhoff, Lab-STICC UMR 6285, Université de Bretagne Occidentale
--
-- Cheddar has been published in the "Agence de Protection des Programmes/France" in 2008.
-- Since 2008, Ellidiss technologies also contributes to the development of
-- Cheddar and provides industrial support.
--
-- The full list of contributors and sponsors can be found in AUTHORS.txt and SPONSORS.txt
--
-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2 of the License, or
-- (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with this program; if not, write to the Free Software
-- Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
--
--
-- Contact : cheddar@listes.univ-brest.fr
--
------------------------------------------------------------------------------
-- Last update :
--    $Rev$
--    $Date$
--    $Author: singhoff $
------------------------------------------------------------------------------
------------------------------------------------------------------------------

package body queueing_system.theoretical.mms is

   procedure initialize
     (a_queueing_system : in out mms_queueing_system_theoretical)
   is
   begin
      initialize (generic_queueing_system_theoretical (a_queueing_system));

      a_queueing_system.queueing_system_type := qs_mms;
   end initialize;

   procedure qs_average_waiting_time
     (a_queueing_system : in     mms_queueing_system_theoretical;
      result            : in out Double)
   is

      arrival_rate : constant Double :=
        a_queueing_system.arrival_rate.entries (0).data;
      service_rate : constant Double :=
        a_queueing_system.service_rate.entries (0).data;
   begin
      result := 1.0 / (service_rate - arrival_rate) - (1.0 / service_rate);
   end qs_average_waiting_time;

   procedure qs_average_number_customer
     (a_queueing_system : in     mms_queueing_system_theoretical;
      result            : in out Double)
   is

      rau : constant Double :=
        a_queueing_system.arrival_rate.entries (0).data /
        a_queueing_system.service_rate.entries (0).data;
   begin
      result := rau / (1.0 - rau);
   end qs_average_number_customer;

   procedure qs_maximum_waiting_time
     (a_queueing_system : in     mms_queueing_system_theoretical;
      result            : in out Double)
   is
   begin
      raise not_implemented;
   end qs_maximum_waiting_time;

   procedure qs_maximum_number_customer
     (a_queueing_system : in     mms_queueing_system_theoretical;
      result            : in out Double)
   is
   begin
      raise not_implemented;
   end qs_maximum_number_customer;

   function get_probability_of_state
     (a_queueing_system : in mms_queueing_system_theoretical;
      n                 : in Natural) return Double
   is
      utilisation : Double;
      result      : Double;
   begin
      utilisation :=
        a_queueing_system.arrival_rate.entries (0).data /
        a_queueing_system.service_rate.entries (0).data;
      result := Pow (utilisation, Double (n));
      result := result * (1.0 - utilisation);
      return (result);
   end get_probability_of_state;

   function get_qs_nb_tasks
     (a_queueing_system : in mms_queueing_system_theoretical) return Double
   is
   begin
      return a_queueing_system.nb_tasks;
   end get_qs_nb_tasks;

   procedure set_qs_nb_tasks
     (a_queueing_system : in out mms_queueing_system_theoretical;
      value             :        Double)
   is
   begin
      a_queueing_system.nb_tasks := value;
   end set_qs_nb_tasks;

   function get_probability_of_queueing
     (a_queueing_system : in mms_queueing_system_theoretical) return Double
   is
      utilisation  : Double;
      adivs        : Double;
      upper_result : Double          := 0.0;
      lower_result : Double          := 0.0;
      lambda       : constant Double := 0.0;

      function factorial (value : in Double) return Double is
         n      : Double := value;
         result : Double := value;
      begin
         while (n > 1.0) loop
            --            Put(" " & N'Img);
            n      := n - 1.0;
            result := result * n;
         end loop;
         return result;
      end factorial;

   begin

      utilisation :=
        a_queueing_system.arrival_rate.entries (0).data /
        a_queueing_system.service_rate.entries (0).data;

      adivs :=
        lambda /
        a_queueing_system.service_rate.entries (0).data /
        a_queueing_system.nb_tasks;

      upper_result :=
        (1.0 / factorial (a_queueing_system.nb_tasks)) *
        (Pow (adivs, a_queueing_system.nb_tasks)) *
        (1.0 / (1.0 - utilisation));

      lower_result := lower_result + 1.0;
      for n in 1 .. Natural (a_queueing_system.nb_tasks) - 1 loop
         lower_result :=
           lower_result +
           (1.0 / factorial (Double (n)) * Pow (adivs, Double (n)));
      end loop;

      lower_result :=
        lower_result +
        (1.0 / factorial (a_queueing_system.nb_tasks)) *
          (Pow (adivs, a_queueing_system.nb_tasks)) *
          (1.0 / (1.0 - utilisation));

      return (upper_result / lower_result);
   end get_probability_of_queueing;

end queueing_system.theoretical.mms;