On Thursday, 6 February 2014 at 13:23:14 UTC, Sönke Ludwig wrote:
Am 06.02.2014 12:37, schrieb Max Klyga:
Anti-GC crowd tries to promote ARC as an deterministic
alternative for
memory management.
I noticed that people promoting ARC do not provide any
disadvantages for
proposed approach.
The thing is in gamedev and other soft-realitime software
background
only a handfull types of resources are really managed by RC
and memory
usage patterns are VERY specific to their domain (mostly linear
allocation/deallocation and objects with non deterministic
lifetime are
preallocated in pools).
Trying to use RC as a general method of memory management
leads to some
problems.
A pretty detailed view by John Harrop (He is somewhat known
for trolling
in PL community, but nonetheless knows what he is talking
about) -
http://www.quora.com/Computer-Programming/How-do-reference-counting-and-garbage-collection-compare/answer/Jon-Harrop-1?srid=3Gvg&share=1#
So RC could also introduce unpredictable pause times at
undesired places.
This is also confirmed by research from HP -
http://www.hpl.hp.com/personal/Hans_Boehm/popl04/refcnt.pdf
My point is that we should not ruin the language ease of use.
We do need
to deal with Phobos internal allocations, but we should not
switch to
ARC as a default memory management scheme. In practice people
promoting
ARC will probably not use phobos anyway. Currently its just an
excuse to
not use D.
Look at c++ and STL, etc. People will roll their own solutions
no matter
what you try.
Full ACK! Reference counting should be well supported, but it
shouldn't be the default scheme or built-in at a low level.
From my personal experience it would be ideal to be able to
customize certain types to be reference counted (allowing the
user full flexibility implementing the actual reference
counting and without ruling out weak references!), but have
them accessible using the same syntax and type conversion
semantics as normal references.
I think the best way forward would be to look at the places in D
where allocations happen, and then figure out how we can
optionally allow reference counting in these situations. Andrei
just made a thread on this yesterday in regard to slices, which I
think are the most promising for a RC solution.
