Re: Multitasking

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

Dennis Lee Bieber fed this fish to the penguins on Saturday 07 December 
2002 01:33 pm:


> [wulfraed@beastie wulfraed]$ ./tt
> a TC task has initiated
> Start Task TC_one at:                48526
> Start Task TC_two at:                48526

        Hmmm, using whole seconds (and why Long_Long yet?) hides some of the 
timing granularity. Let's try again with a bit more detail, and a 
second invocation of the entry calls so you can see the effect of a 
rendezvous blocking action.

        Try this one, which overlaps a few invocations to each task. (My 
apologies for the clumsy myPutFloat definition -- no doubt there is a 
more efficient way of doing the same without coding the fore/aft/exp 
arguments on all calls -- while I've always liked the language [did a 
presentation on Ada in my senior year, before the it had even been 
finalized as a DOD standard] I've never really /used/ the language).


with Ada.Text_IO; use Ada.Text_IO;
with Ada.Calendar; use Ada.Calendar;
with Ada.Float_Text_IO; use Ada.Float_Text_IO;

Procedure tt is

        procedure myPutFloat(F : Float) is
        begin
                Put(F, Fore=>6, Aft=>5, Exp=>0);
        end;
        
        task type TC is
                entry S(D : Positive);
        end TC;

        task body TC is
                delayID : Positive;
        begin
                Put("a TC task has initiated at: ");
                myPutFloat(Float(Seconds(Clock)));
                New_Line;
                loop
                        select
                                Accept S(D : In Positive) do
                                        myPutFloat(Float(D));
                                        Put(" Accepted at: ");
                                        myPutFloat(Float(Seconds(Clock)));
                                        New_Line;
                                        delayID := D;
                                end S;
                        or
                                terminate;
                        end select;
                        
                        delay Standard.duration(delayID);

                        Put("Task ");
                        myPutFloat(Float(delayID));
                        Put(" has finished at ");
                        myPutFloat(Float(Seconds(Clock)));
                        New_Line;
                end loop;
        end TC;

        TC_one, TC_two : TC;

begin
        Put("Rendezvous Task TC_one at: ");
        myPutFloat(Float(Seconds(Clock)));
        New_Line;
        TC_one.S(120);
        
        Put("Rendezvous Task TC_two at: ");
        myPutFloat(Float(Seconds(Clock)));
        New_Line;
        TC_two.S(60);
        
        Put("Both tasks should be running");
        New_Line;

        Put("Rendezvous Task TC_two at: ");
        myPutFloat(Float(Seconds(Clock)));
        New_Line;
        TC_two.S(10);

        Put("Rendezvous Task TC_one at: ");
        myPutFloat(Float(Seconds(Clock)));
        New_Line;
        TC_one.S(20);

        Put("Rendezvous Task TC_two at: ");
        myPutFloat(Float(Seconds(Clock)));
        New_Line;
        TC_two.S(15);
        
        Put("Waiting for last task to finish");
        New_Line;
end tt;

        The results on my machine are:

[wulfraed@beastie ada]$ ./tt
a TC task has initiated at:  58287.18750
Rendezvous Task TC_one at:  58287.18750
   120.00000 Accepted at:  58287.18750
Rendezvous Task TC_two at:  58287.19141
a TC task has initiated at:  58287.19141
    60.00000 Accepted at:  58287.19141
Both tasks should be running
Rendezvous Task TC_two at:  58287.19141
Task     60.00000 has finished at  58347.19141
    10.00000 Accepted at:  58347.19141
Rendezvous Task TC_one at:  58347.19141
Task     10.00000 has finished at  58357.20313
Task    120.00000 has finished at  58407.19141
    20.00000 Accepted at:  58407.19141
Rendezvous Task TC_two at:  58407.19141
    15.00000 Accepted at:  58407.19141
Waiting for last task to finish
Task     15.00000 has finished at  58422.20313
Task     20.00000 has finished at  58427.20703


-- 
 > ============================================================== <
 >   wlfraed@ix.netcom.com  | Wulfraed  Dennis Lee Bieber  KD6MOG <
 >      wulfraed@dm.net     |       Bestiaria Support Staff       <
 > ============================================================== <
 >        Bestiaria Home Page: http://www.beastie.dm.net/         <
 >            Home Page: http://www.dm.net/~wulfraed/             <