Re: Multitasking

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

arvids lemchens fed this fish to the penguins on Saturday 07 December 
2002 04:16 am:

> type TCPtr is access TC;
> type TList is array (Positive range <>) of TCPtr;
> CList : TList(1..10000);
>
        Let's see, you create an array of pointers capable of accessing 10_000 
copies of the task...
 
> begin
>    CList(1) := new TC;

        But you only create ONE task in the main body

>    Put("Start Task S at: ");
>    Put(Long_Long_Integer(Seconds(Clock)));
>    New_Line;
>    CList(1).S(60);

        You then call a rendezvous entry, which means main body holds here 
until the task exits the accept block -- but the accept block contains 
a delay statement so both the main body and the task basically do 
nothing for a while, then the task does its output and finishes the 
accept block, at which point the main body continues (and the task goes 
back to waiting for another entry call to be made).

>    Put("End Task S ");
>    Put(Long_Long_Integer(Seconds(Clock)));
>    New_Line;
>    Put("Start Task U ");
>    Put(Long_Long_Integer(Seconds(Clock)));
>    New_Line;
>    CList(1).S(120);

        And now you make a second rendezvous with the SAME task.

>    Put("End Task U ");
>    Put(Long_Long_Integer(Seconds(Clock)));
>    New_Line;
> end tt;


        Looks like it's doing just what you asked for (which may not be what 
you meant).

        The following hacked version of your code (and I see that if I do much 
Ada work in Mandrake I'm going to have to figure out how to set the 
default vim tab stops to 4)


with Ada.Text_IO; use Ada.Text_IO;
with Ada.Calendar; use Ada.Calendar;
with Ada.Long_Long_Integer_Text_IO; use Ada.Long_Long_Integer_Text_IO;

Procedure tt is

        task type TC is
                entry S(D : Positive);
        end TC;

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

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

        TC_one, TC_two : TC;

begin
        Put("Start Task TC_one at: ");
        Put(Long_Long_Integer(Seconds(Clock)));
        New_Line;
        TC_one.S(120);
        
        Put("Start Task TC_two at: ");
        Put(Long_Long_Integer(Seconds(Clock)));
        New_Line;
        TC_two.S(60);
        
        Put("Both tasks should be running");
        New_Line;
end tt;


generates the following output:

[wulfraed@beastie wulfraed]$ ./tt
a TC task has initiated
Start Task TC_one at:                48526
Start Task TC_two at:                48526
a TC task has initiated
Both tasks should be running
Task                   60 has finished at                48586
Task                  120 has finished at                48646

        Note: I get lucky, and the I/O overlap managed to appear at the 
newlines, but with slightly different overhead, it is possible that the 
"a TC task has initiated" could appear between the "... at:     " and " 
    <clock>" output.

        Also note that I made TC_one run for the longer period of time <G>


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