[Pharo-project] Another fixes to finalization (was Re: [update 1.2] #12161 - #12172)
leves at elte.hu
Mon Oct 4 19:06:35 EDT 2010
On Tue, 5 Oct 2010, Igor Stasenko wrote:
> 2010/10/4 Levente Uzonyi <leves at elte.hu>:
> On Mon, 4 Oct 2010, Igor Stasenko wrote:
>> On 4 October 2010 22:51, Henrik Sperre Johansen
> <henrik.s.johansen at veloxit.no> wrote:
>> On 04.10.2010 21:47, Igor Stasenko wrote:
>>> On 4 October 2010 22:09, Stéphane Ducasse<stephane.ducasse at inria.fr>
>>>> so let us know in the bug entry what is the conclusion :)
>>> I think someone should verify my benchmarks i.e.
>>> [ self loadsomething ] timeToRun
>>> before and after patch.
>>> And conclusion is better be written by Henrik, because he's having
>>> concerns about speed,
>>> while i don't. :)
>> I already have:
> emm.. wait.
> WeakKeyDict should not delete associations with nil-ed keys
> automatically, because otherwise
> you won't be able to use it in weak finalization scheme.
> There is two distinct use cases of weak-key dicts:
> a) for weak finalization
> b) for attaching some extra info(value) per object(key), which can be
> automatically discarded once object become garbage
> so, while in case (b) you can mercilessly kill/reuse associations with
> nil keys, once they discovered
> in case (a) you should preserve them until there is explicit request
> from outside to finalize values.
> The need in (a), apparently prohibits from using (b) in most efficient
> So, i think, the solution would be to introduce a specialized weak-key
> dicts, which can work much better for (b).
> Squeak's implementation works well in both cases.
Trust me, scanning a whole dict to detect nil keys is not what can be
called 'well' :)
My point is, that these two scenarios should use different classes/implementors
each optimized for own case.
Moreover, case (b) comes from the inability to dynamically add extra
slot(s) to object,
It can be done better, with extra VM features, but without those, it's
pretty close to best possible solution IMHO.
There are already two different classes for a) and b): WeakRegistry
and WeakKeyDictionary (and subclasses).
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