On Monday, 19 November 2012 at 19:14:43 UTC, Jonathan M Davis wrote:

I'd never even _heard_ of half types before this discussion came up. But then
again, the same goes for SIMD. And IIRC, there was some sort of function
attribute relating to pointers and registers that you or some other gaming
person was insisting on a while back, and I'd never heard of it existing in
C++ either (as an extension or otherwise). You clearly program in a very
different world than I do. I care about high performance in what I do but
nothing on _that_ level. I suspect that this is another one of those things
that certain folks would really like to have, and most of the rest of us don't
have any real interest in and often know nothing about in the first place. I
don't know that I really care whether it's added to the language though. I'll
leave that sort of decision up to Walter.

If anything, I just find it interesting how many low level things folks like
you keep coming up with as must-haves or very strong wants that I've never
even heard of and will almost certainly never care about aside perhaps from
how having them in D might help D catch on.

- Jonathan M Davis

Anyone interested in the low precision float types, and what they are good for, can start here
http://www.opengl.org/wiki/Small_Float_Formats

I did not read through all of this thread, but my guess is that the people making the request for half float are mostly into game development and image processing.

When I first started investigating D as a potential C++ replacement, I noted that a lot of the "visible" development (what I could see being publicized) was game development, so it seemed that for some reason a lot of the D users were also game developers, so there's perhaps something about D that they find attractive.

I've said it before, but I think D has MASSIVE potential in gaming. We are an industry crying our for salvation from C++, but there's no possibility to compromise on the level of access it provides us to the hardware we work with.

D is the only language I know of that seriously threatens to offer modern programming constructs, while still providing a syntax and compiler technology that I can easily understand in terms of code generation and can hit the metal when I need to.

Additionally, most games programmers have very long-term relationships with C++ almost exclusively, so despite hating it, moving to something utterly different like rust or whatever cool thing comes along will just never fly. You'll never convince a team of 10-30 programmers to agree on such a change all at once, and re-training staff in something so foreign would never be economical.

D is again particularly interesting here because it's enough like C++ and C# that programmers feel immediately comfortable and somewhat liberated, but not threatened. Also, in a lot of cases, the changes to D are relatively intuitive. The things you expect should work, often just do... but there are still lots of rough edges too.

Gaming is a very demanding and progressive field of software, but also very backwards at the same time. It's a sort of unity between many disciplines, and it all comes together under a performance critical and usually embedded umbrella, in a highly competitive and fickle industry.

You can't tell the customer to upgrade their hardware when it needs to run on a console with an ~8 year lifecycle. As a (tech/engine) programmer, if you don't scrutinise the code generation, calling conventions, memory access patterns, data layout and sizes, the competition will, and their product will appear superior. Towards the end of that 8 year cycle, programmers are REALLY squeezing these machines. If the language doesn't support that, then you can't compete anymore, hence we remain stuck on C++ (and there are many instances where the industry is reverting to C because C++ is a bloaty pig).

Why game devs are interested so much in D is interesting considering the GC is noted to be a problem for game devs. The work of H. S. Teoh comes to mind with his work on a game engine, that pushed the limits of the GC and std lib.

I'll admit this is my biggest fear hands down!

That said, D is the only GC based language I know if where the GC is relatively optional. This allows us to hedge our bets, and ease in to it slowly as we gain confidence and understanding of how it behaves.

I don't yet have much confidence in the GC, and generally avoid using it. I only use it for short term allocations, or non-critical-loop work which often only survive for the scope of the function.

I don't have enough experience to make any reasonable claims about its affect on performance, but I have seen a lot of benchmarks in this NG though that have shown it is significantly inferior to C# and Java. That doesn't fill me with confidence.

I do hope work is done to make it at least competitive with java/C#'s GC, and then we'll see where we stand. C#'s GC is proven to be acceptable in at least smaller/independent games. It's probably still not acceptable on major AAA console titles though. We need thread-local collection... it can't stop the world to do a collect, and I wouldn't afford more than 1ms at any given time (and I think that's even being generous). Perhaps incremental collection where it would stop after it reaches its allocated time budget or something?

So my working theory is, if the GC were limited to relatively few 'convenience allocations' and the bulk of memory was still managed manually, maybe that will lift the load to the point that the cost is insignificant, and it will be a useful tool...?

But yes, for the moment, we use malloc and emplace.

I think this will mature only with experience and it'll help if there are receptive ears to our needs. It's impossible for us to complain to the C# guys about the habits of their GC and expect anyone to care. This community offers options.

We don't HATE garbage collection, we just can't generally afford it.

In any case, the point is that I don't think the D community should overlook what the game devs are doing, they're pushing D to its limits and are making D more visible than perhaps anyone.

This is about the only thing of significance I think we can hope to offer back to the community. If we can use it successfully in a major commercial game, then tell the story afterwards, I think that could bring a lot of new interest. I hope we are able to do that.

I think maturity is reaching the point where people can realistically start to consider taking a risk with it.

I'd love to see more movement on the android/ios front, I reckon there's a lot more immediate potential in that space given that it's a lot less risky and the bar isn't as high.