Re: Selective accept in Ada tasking

[Peter Hermann <ica2ph@iris16.csv.ica.uni-stuttgart.de>]

Ivan Paniagua <paniaguaivan@hotmail.com> wrote:
> I'm using GNAT 3.14 in a Windows XP platform. If I introduce a delay
> before de end loop all it's OK, but what I want is that the task keep
> sleeping till it has a call to an entry without consuming a lot of CPU
> time.

I am using GNAT3.15p windows2000 CPU600MHz.
The delay within the loop of the accepting task seems not be justified
IMHO because this task should be constantly alert and working on demand.
The consumer task on the other side defines the needs and if necessary,
the CPU then goes up to 100%, of course. If not, then not :-)
The following code shows a pretty CPU usage profile in windows task manager:

procedure paniaguaivan is

  value : float := 0.0;
  fin : boolean := false;

--From: paniaguaivan@hotmail.com (Ivan Paniagua)
--Newsgroups: comp.lang.ada
--Subject: Selective accept in Ada tasking
--Date: 27 Nov 2002 00:22:41 -0800   Wed Nov 27 09:33:53 2002
--Organization: http://groups.google.com/
--Lines: 28

--I'm a beginner and I have a problem. This code makes my CPU reach 100%:

procedure work is begin
for i in 1..1e7 loop
  value := float(i+i)+0.5;
end loop;
end work;

task Man_Motor1 is
  entry subir;
  entry bajar;
  entry parar;
end Man_Motor1;
task body Man_Motor1 is
begin
	while not Fin loop
		select			
			accept Subir; --aufstehen, go up, monter
			work;--null; -- Some actions
		or
			accept Bajar; -- come down
			null; -- Some actions
		or
			accept Parar; -- anhalten, die, stoj
			null; -- Some actions
		or
			terminate;
		end select;
	end loop;
end Man_Motor1;

--I'm using GNAT 3.14 in a Windows XP platform. If I introduce a delay
--before de end loop all it's OK, but what I want is that the task keep
--sleeping till it has a call to an entry without consuming a lot of CPU
--time.

--Can anybody help me?
--Thank you very much.
begin
  loop
    Man_Motor1.subir;
    Man_Motor1.bajar;
    Man_Motor1.parar;
    delay 3.0;
  end loop;
end paniaguaivan;

-- 
--Peter Hermann(49)0711-685-3611 fax3758 ica2ph@csv.ica.uni-stuttgart.de
--Pfaffenwaldring 27 Raum 114, D-70569 Stuttgart Uni Computeranwendungen
--http://www.csv.ica.uni-stuttgart.de/homes/ph/
--Team Ada: "C'mon people let the world begin" (Paul McCartney)