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From: "christopher.orihuela@gmail.com" <christopher.orihuela@gmail.com>
Newsgroups: comp.lang.ada
Subject: Weird problem with recursion and tasks
Date: 2 Dec 2006 19:21:14 -0800
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Date: 2006-12-02T19:21:14-08:00
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I was implementing a concurrent version of QuickSort (each half in a
different task) when I realized that sometimes the recursive task
didn't execute.
=BFCould anybody tell me why for values of MaxI > 4 I allways get a
higer count of A in the following program? Thanks.


With Ada.Text_IO;
Use Ada.Text_IO;

Procedure My_Proc is

   protected type Counter is
      Procedure IncA;
      Procedure IncB;
      Procedure ShowCounts;
   private
      A, B: Natural :=3D 0;
   end Counter;

   protected body Counter is
      Procedure IncA is
      begin
         A :=3D A+1;
      end IncA;
      Procedure IncB is
      begin
         B :=3D B+1;
      end IncB;
      Procedure ShowCounts is
      begin
         Put_Line("A: " & Integer'Image(A));
         Put_Line("B: " & Integer'Image(B));
      end ShowCounts;
   end Counter;

   MyCounter : Counter;

   Procedure Recursive (I : Natural; MaxI : Natural) is
   begin

      if (I >=3D MaxI) then
           return;
      end if;

      MyCounter.IncA;
      MyCounter.IncA;
      declare
         Task My_Recursive_Task;
         Task Body My_Recursive_Task is
         begin
            Recursive(I+1, MaxI);
            MyCounter.IncB;
         end My_Recursive_Task;

      begin
         Recursive(I+1, MaxI);
         MyCounter.IncB;
      end;
   end Recursive;
  =20
begin
   Recursive (1, 6);
   MyCounter.ShowCounts;
end My_Proc;