On Sat, 01 Feb 2014 02:15:42 -0800, Manu <[email protected]> wrote:
On 1 February 2014 19:27, Adam Wilson <[email protected]> wrote:
On Fri, 31 Jan 2014 23:35:44 -0800, Manu <[email protected]> wrote:
On 1 February 2014 16:26, Adam Wilson <[email protected]> wrote:
On Fri, 31 Jan 2014 21:29:04 -0800, Manu <[email protected]> wrote:
On 26 December 2012 00:48, Sven Over <[email protected]> wrote:
std.typecons.RefCounted!T
core.memory.GC.disable();
Wow. That was easy.
I see, D's claim of being a multi-paradigm language is not false.
It's not a realistic suggestion. Everything you want to link uses the
GC,
and the language its self also uses the GC. Unless you write
software in
complete isolation and forego many valuable features, it's not a
solution.
Phobos does rely on the GC to some extent. Most algorithms and
ranges
do
not though.
Running (library) code that was written with GC in mind and
turning
GC
off
doesn't sound ideal.
But maybe this allows me to familiarise myself more with D. Who
knows,
maybe I can learn to stop worrying and love garbage collection.
Thanks for your help!
I've been trying to learn to love the GC for as long as I've been
around
here. I really wanted to break that mental barrier, but it hasn't
happened.
In fact, I am more than ever convinced that the GC won't do. My
current
#1
wishlist item for D is the ability to use a reference counted
collector
in
place of the built-in GC.
You're not alone :)
I write realtime and memory-constrained software (console games), and
for
me, I think the biggest issue that can never be solved is the
non-deterministic nature of the collect cycles, and the unknowable
memory
footprint of the application. You can't make any guarantees or
predictions
about the GC, which is fundamentally incompatible with realtime
software.
Language-level ARC would probably do quite nicely for the
miscellaneous
allocations. Obviously, bulk allocations are still usually best
handled
in
a context sensitive manner; ie, regions/pools/freelists/whatever, but
the
convenience of the GC paradigm does offer some interesting and
massively
time-saving features to D.
Everyone will always refer you to RefCounted, which mangles your
types
and
pollutes your code, but aside from that, for ARC to be useful, it
needs
to
be supported at the language-level, such that the language/optimiser
is
able to optimise out redundant incref/decref calls, and also that it
is
compatible with immutable (you can't manage a refcount if the object
is
immutable).
The problem isn't GC's per se. But D's horribly naive implementation,
games are written on GC languages now all the time (Unity/.NET). And
let's
be honest, games are kind of a speciality, games do things most
programs
will never do.
You might want to read the GC Handbook. GC's aren't bad, but most,
like
the D GC, are just to simplistic for common usage today.
Maybe a sufficiently advanced GC could address the performance
non-determinism to an acceptable level, but you're still left with the
memory non-determinism, and the conundrum that when your heap
approaches
full (which is _always_ on a games console), the GC has to work harder
and
harder, and more often to try and keep the tiny little bit of overhead
available.
A GC heap by nature expects you to have lots of memory, and also lots
of
FREE memory.
No serious console game I'm aware of has ever been written in a
language
with a GC. Casual games, or games that don't attempt to raise the bar
may
get away with it, but that's not the industry I work in.
That's kind of my point. You're asking for massive changes throughout
the
entire compiler to support what is becoming more of an edge case, not
less
of one. For the vast majority of use cases, a GC is the right call and D
has to cater to the majority if it wants to gain any significant
mindshare
at all. You don't grow by increasing specialization...
Why is ARC any worse than GC? Why is it even a compromise at the high
level?
Major players have been moving away from GC to ARC in recent years. It's
still a perfectly valid method of garbage collection, and it has the
advantage that it's intrinsically real-time compatible.
Define Major Players? Because I only know about Apple, but they've been
doing ARC for almost a decade, and IIRC, like GC's, it's not universally
loved there either. Microsoft is desperately trying to get people to move
back to C++ but so far the community has spoken with a resounding "You can
pry C#/.NET from our cold, dead, hands." Java has shown no particular
interest in moving away from GC's probably because their GC is best in
class. Even games are starting to bring in GC's (The Witcher 2 for
example, and almost all of the mobile/casual games market, which is
actually monetarily bigger than the triple-A games market.)
I don't think realtime software is becoming an edge case by any means,
maybe 'extreme' realtime is, but that doesn't change the fact that the GC
still causes problems for all realtime software.
Yes, but my point is that there is very little real-time software written
as a percentage of all software written, which, by definition, makes it an
edge-case. Even vehicle control software is no longer completely
real-time. [I just happen to know that because that's the industry I work
in. Certain aspects are, with the rest scheduled out.] And more to the
point, D has made no claim about it's suitability for RT software and I
have seen little demand for it outside a very small very vocal minority
that is convinced that it has the dynamic resource management panacea if
everyone would just do as they say.
I personally believe latency and stuttering is one of the biggest
usability
hindrances in modern computing, and it will become a specific design
focus
in software of the future. People are becoming less and less tolerant of
latency in all forms; just consider the success of iPhone compared to
competition, almost entirely attributable to the silky smooth UI
experience. It may also be a telling move that Apple switched to ARC
around
the same time, but I don't know the details.
I use .NET every day, seriously not one day goes by when I haven't touched
some C# code. I can happily report that you are *ahem* wrong. Even Visual
Studio 2013 doesn't stutter often, and only when I am pulling in some
massive third-party module that may or may not be well written.
Ironically, it is VisualD, it of D code fame that most slows down VS for
me. I write software in C# every day I can happily report that I have yet
to have a problem with stuttering in my code that wasn't of my own devise.
(If you forget to asynchronously call that web-service it WILL stutter)
And that's a point. I can write software in C# that works will without
having to worry about circular references or if my data prematurely falls
out of scope or any other of the details that are associated with ARC. And
for my not-effort, I pay an effective cost of 0. Win-win. You're demanding
that to suit your needs, we make a massive philosophical and language
change to D that will incur HIGHER cognitive load on programmers for
something that will not measurably improve the general use case? Ahem,
that's good for D how?
I also firmly believe that if D - a native compiled language familiar to
virtually all low-level programmers - doesn't have any ambition to
service
the embedded space in the future, what will? And why not?
The GC is the only thing inhibiting D from being a successful match in
that
context. ARC is far more appropriate, and will see it enter a lot more
fields.
What's the loss?
Cognitive load. How many details does the programmer have to worry about
per line of code. Ease-of-use. A GC is easier to use in practice. You can
say well they should learn to use ARC because it's better (for certain
definitions of better) but they won't. They'll just move on. I'd say
that's a pretty big loss.
And based on my conversations with Walter, I don't think that D was ever
intended to make a play for the embedded space. If D can be made to work
there great, but Walter, as near as I can tell, has no interest in tying
the language in knots to make it happen. So that's a non-issue. And let's
be honest, the requirements of that space are fairly extreme.
I think it's also telling that newcomers constantly raise it as a massive
concern, or even a deal-breaker. Would they feel the same about ARC? I
seriously doubt it. I wonder if a poll is in order...
Conversely, would any of the new-comers who are pro-GC feel any less
happy
if it were ARC instead? $100 says they probably wouldn't even know, and
almost certainly wouldn't care.
I DON'T see a majority of newcomers raising an issue with the GC, I only
see it from newcomers with some pretty extreme latency requirements,
primarily for the real-time crowd. The majority of newcomers aren't
interested in RT work. I think you're falling prey to confirmation bias
here.
--
Adam Wilson
GitHub/IRC: LightBender
Aurora Project Coordinator
