dynamically create tasks

dynamically create tasks

[compguy45]

If you have one task body and would like to create 5 of these tasks since there is one task body there will only be one task created plus main task....how would you create 20 tasks with same body?
is there way to do this?

Re: dynamically create tasks

[Shark8]

On 10/10/2014 7:49 PM, compguy45@gmail.com wrote:
> If you have one task body and would like to create 5 of these
> tasks since there is one task body there will only be one
> task created plus main task....how would you create 20 tasks
> with same body?
>
> is there way to do this?

Yes; it's essentially what I do in my solution to the No-Connection 
puzzle on Rosetta-code.
( See: http://rosettacode.org/wiki/Solve_the_no_connection_puzzle#Ada )

The Idea is that the tasks are fed a list of possible numbers and a 
state (usu. inherited from prior tasks which create them dynamically) -- 
if the given state cannot be a solution, its task simply ends otherwise 
there are two options (1) the state is a complete board [that is, the 
puzzle is solved], OR (2) the task creates a task for every possible 
number which can be in the next position.

Re: dynamically create tasks

[Niklas Holsti]

On 14-10-11 04:49 , compguy45@gmail.com wrote:
> If you have one task body and would like to create 5 of these
> tasks since there is one task body there will only be one task
> created plus main task....how would you create 20 tasks with same body?
> is there way to do this?
> 

Use task types. Instead of saying

   task My_Own_Task is
   ...
   end My_Own_Task;

say

   task type My_Own_Task is
   ...
   end My_Own_Task;

The "task body" part stays the same. Then you can create as many tasks
as you like, of this type, using what looks like a normal variable
declaration:

   Thinker, Doer, Builder, Painter : My_Own_Task;

and now all these tasks are running. You can also create arrays of tasks
in the normal way, " ... array ( ... ) of My_Own_Task", you can have
access types for tasks and use "new My_Own_Task", and so on.

(However, I would suffix task-type names with "_T", just as I do for
other types, so I would write My_Own_Task_T for the task-type name.)

Note that when you use a task type and have several tasks with the same
body, there must be some way for each task to know what *it* should do;
all tasks should of course not do exactly the same thing. One way is to
add an entry to each task and call these entries to give different
parameters to each task; another way is for each task to call some
central task or protected object to get their different parameters. You
can also give the task type discriminants that tell each task what to
do; that may be useful if you create tasks dynamically (wth "new").

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .

Re: dynamically create tasks

[compguy45]

Yes thats what i am confused about lots of tasks same body ? I have to dinamucally create tasks  and then first tasks will get called by main. Then first tasks will call that same entry on tasks 2. Then task 2 will call same entry on task 3. Then when last task is called task n then it will go all the wayback to task 1 (which waited all this time) which will now know thats all tasks have been notified

Re: dynamically create tasks

[Dmitry A. Kazakov]

On Sat, 11 Oct 2014 06:02:07 -0700 (PDT), compguy45@gmail.com wrote:

> Yes thats what i am confused about lots of tasks same body ? I have to
> dinamucally create tasks  and then first tasks will get called by main.
> Then first tasks will call that same entry on tasks 2. Then task 2 will
> call same entry on task 3. Then when last task is called task n then it
> will go all the wayback to task 1 (which waited all this time) which will
> now know thats all tasks have been notified

Or you signal a pulse event to notify all tasks at once.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Re: dynamically create tasks

[compguy45]

I cant.  I have to sync it using entries.   

Re: dynamically create tasks

[Ludovic Brenta]

compguy45@gmail.com writes:
> I cant.  I have to sync it using entries.   

Sounds like homework assignment.

-- 
Ludovic Brenta.

Re: dynamically create tasks

[Brad Moore]

On 14-10-11 10:34 AM, compguy45@gmail.com wrote:
> I cant.  I have to sync it using entries.
>

There are a number of unknown requirements here.
Are the tasks to be dynamically created on the stack, or on the heap?
Can the sync be by task entries, or by protected object entries?
How does a task determine which one is the next to be signalled? Can the 
tasks be in an array, and an incrementing array index be used to 
determine the next one, or does the task need to be linked more 
dynamically, such as by a linked list of tasks?

I presume this is a homework assignment, and that the exercise is to 
involve only task entry calls, and that otherwise the other details are 
left to the student.

An interesting solution would be one that lets you arbitrarily hook 
individual tasks together that are created either dynamically on the 
stack (as a task declaration), or dynamically from the heap (via the new 
keyword).

For this, I'd suggest having a Connect task entry that accepts an access 
type for the task as a parameter.

     entry Connect (Next_Task : T_Access);

This can be used to connect the tasks together in a circular list.

Then another entry to Signal a task, and another that the main task can 
call to wait for the initial Signalled task to accept once the initially 
signalled task has signalled by the previous task in the task ring.

eg.
    entry Signal;
    entry Wait_For_All_Tasks;


Good luck.

Re: dynamically create tasks

[Simon Wright]

compguy45@gmail.com writes:

> If you have one task body and would like to create 5 of these tasks
> since there is one task body there will only be one task created plus
> main task....how would you create 20 tasks with same body?  is there
> way to do this?

   task type T is
      ...
   end T;

   Tasks : array (1 .. 20) of T;

   ...

   task body T is
   ...
   end T;

See ARM 9.1(2), vs single_task_declaration, (3).