[gecode-users] Space::force and Space::unforce

[Mikael Zayenz Lagerkvist]

Hi,

The force/unforce members makes sure that the dispose-member is called
when the Space is deleted. However, there are other circumstances
where a propagator is disposed but the Space lives on. One such case
is when a propagator is subsumed, another is when rewriting is done.
In these cases the propagator should clean up after itself, for
example by making sure to cancel subscriptions and returning any
space-allocated memory. Unless you have references to external data,
the kind of clean-up done in dispose is not necessary when a space is
deleted.

Cheers,
Mikael

On Wed, Dec 3, 2008 at 1:28 PM, David Rijsman <David.Rijsman at quintiq.com> wrote:
> Hi Mikael,
>
> thanks, what is the use of BinaryPropagator::dispose if this class does not register itself  (it does not use force nor unforce)?
>
> David
>
>>>>
> From:   "Mikael Zayenz Lagerkvist" <zayenz at gmail.com>
> To:     "David Rijsman" <David.Rijsman at quintiq.com>
> CC:     <users at gecode.org>
> Date:   12/3/2008 1:22 PM
> Subject:        Re: [gecode-users] Space::force and Space::unforce
>
> Hi,
>
> The functions force(Space*) and unforce(Space*) are members of the
> Actor-class [1], and are used to register and deregister propagators
> that have references to data that is external to the space. The
> layered graph propagator, for example, has a reference to a DFA that
> is shared. If a propagator does not register for deletion, then the
> dispose-member will not be run when a space is deleted.
>
> Note that the members force(Space*) and unforce(Space*) will be
> replaced in Gecode 3.0.0 with the more general Space-members notice
> and ignore.
>
> Cheers,
> Mikael
>
> [1] http://www.gecode.org/gecode-doc-latest/classGecode_1_1Actor.html#e32f558bd1d470b3f9bbb8283a282678
>
> On Wed, Dec 3, 2008 at 12:58 PM, David Rijsman
> <David.Rijsman at quintiq.com> wrote:
>> I am implementing my own propagator and I am looking at different implementations. In LayeredGraph for example I see the use of Space::force and Space::unforce but in other propagators I do not see such a use. When should I use the force and unforce and for what purpose?
>>
>> thanks,
>>
>> David
>>
>>
>>
>>
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>
>
>
> --
> Mikael Zayenz Lagerkvist, http://www.ict.kth.se/~zayenz/
>
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-- 
Mikael Zayenz Lagerkvist, http://www.ict.kth.se/~zayenz/