Why I Like D

[Stanislav Blinov]

On Wednesday, 12 January 2022 at 16:17:02 UTC, H. S. Teoh wrote:
> On Wed, Jan 12, 2022 at 03:41:03PM +0000, Adam D Ruppe via 
> Digitalmars-d-announce wrote:
>> On Wednesday, 12 January 2022 at 15:25:37 UTC, H. S. Teoh 
>> wrote:
>> > 	However it turns out that unless you are writing a computer
>> > 	game, a high frequency trading system, a web server
>> 
>> Most computer games and web servers use GC too.
> [...]
>
> Depends on what kind of games, I guess. If you're writing a 
> 60fps real-time raytraced 3D FPS running at 2048x1152 
> resolution, then *perhaps* you might not want a GC killing your 
> framerate every so often.
>
> (But even then, there's always GC.disable and @nogc... so it's 
> not as if you *can't* do it in D. It's more a psychological 
> barrier triggered by the word "GC" than anything else, IMNSHO.)
>
>
> T

Oh there is a psychological barrier for sure. On both sides of 
the, uh, "argument". I've said this before but I can repeat it 
again: time it. 4 milliseconds. That's how long a single 
GC.collect() takes on my machine. That's a quarter of a frame. 
And that's a dry run. Doesn't matter if you can GC.disable or 
not, eventually you'll have to collect, so you're paying that 
cost (more, actually, since that's not going to be a dry run). If 
you can afford that - you can befriend the GC. If not - GC goes 
out the window.

In other words, it's only acceptable if you have natural pauses 
(loading screens, transitions, etc.) with limited resource 
consumption between them OR if you can afford to e.g. halve your 
FPS for a while. The alternative is to collect every frame, which 
means sacrificing a quarter of runtime. No, thanks.

Thing is, "limited resource consumption" means you're 
preallocating anyway, at which point one has to question why use 
the GC in the first place. The majority of garbage created per 
frame can be trivially allocated from an arena and "deallocated" 
in one `mov` instruction (or a few of them). And things that 
can't be allocated in an arena, i.e. things with destructors - 
you *can't* reliably delegate to the GC anyway - which means your 
persistent state is more likely to be manually managed.

TLDR: it's pointless to lament on irrelevant trivia. Time it! Any 
counter-arguments from either side are pointless without that.