------------------------------------------------------------------------------
------------------------------------------------------------------------------
-- 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;