Re: Multitasking and containers

[Matthew Heaney <matthewjheaney@earthlink.net>]

Maciej Sobczak <no.spam@no.spam.com> writes:

> That would be interesting, but would break apart when encapsulated within a
> protected object, because there multiple readers would be allowed.

But I think that's true only when multiple readers are calling protected
functions.  (There is a subtle difference in semantics between protected
functions and protected procedures.)  It does seem you'd need to use a
protected procedure when manipulating a container nested inside a protected
object, since a protected function wouldn't provide the level of
synchronization required.


> Having a mutex for readers sounds like a concurrency killer and relying on
> protected wrappers seems to be fragile because of this possible
> mutability. So - what is The Solution (tm) for multiple tasks reading from
> the same container?

Declare the container object inside a protected object, and use protected
procedures to manipulate the container.  Protected wrappers should be fine, as
long as you use protected procedures, not protected functions.


> Let's say you want to have N worker tasks consulting a shared dictionary
> (map) that was initialized before the tasks started their work. How would you
> solve this?

As above: declare the container object inside a protected object, and use
protected procedures to manipulate the container.