D on next-gen consoles and for game development

[Dmitry Olshansky]

24-May-2013 09:02, Manu пишет:
> On 24 May 2013 14:11, Marco Leise <Marco.Leise at gmx.de
> <mailto:Marco.Leise at gmx.de>> wrote:
>
>     Am Thu, 23 May 2013 20:21:47 -0400
>     schrieb "Jonathan M Davis" <jmdavisProg at gmx.com
>     <mailto:jmdavisProg at gmx.com>>:
>
>      > At some point, we're probably going to need to
>      > benchmark stuff more agressively and optimize Phobos in general
>     more, because
>      > it's the standard library. And eliminating unnecessary memory
>     allocations
>      > definitely goes along with that.
>      >
>      > - Jonathan M Davis
>
>     On a related note, a while back I benchmarked the naive Phobos
>     approach to create a Windows API (wchar) string from a D
>     string with using alloca to convert the string on a piece of
>     stack memory like this: http://dpaste.1azy.net/b60d37d4
>     IIRC it was 13(!) times faster for ~100 chars of English text
>     and 5 times for some multi-byte characters.
>     I think this approach is too hackish for Phobos, but it
>     demonstrates that there is much room.
>
>
> I don't think it's hack-ish at all, that's precisely what the stack is
> there for. It would be awesome for people to use alloca in places that
> it makes sense.
> Especially in cases where the function is a leaf or leaf-stem (ie, if
> there is no possibility of recursion), then using the stack should be
> encouraged.
> For safety, obviously phobos should do something like:
>    void[] buffer = bytes < reasonable_anticipated_buffer_size ?
> alloca(bytes) : new void[bytes];
>
> toStringz is a very common source of allocations. This alloca approach
> would be great in those cases, filenames in particular.

Alternatively just make a TLS buffer as scratchpad and use that everywhere.

-- 
Dmitry Olshansky