Slow code, slow

[Dmitry Olshansky]

On Saturday, 24 February 2018 at 00:21:06 UTC, Andrei 
Alexandrescu wrote:
> On 2/23/18 3:15 PM, H. S. Teoh wrote:
>> 
>> tl;dr: A trivial piece of code, written as ostensibly 
>> "idiomatic D" with.  Makes me cringe every time I hear
>> "fast code, fast". Our old slogan is a much more accurate 
>> description of
>> the current state of things.)
>
> cc Dmitry
>
> Thanks for a solid bug report. The right response here is to 
> live into our "fast code, fast" principle. It might be the case 
> that the slowdown is actually the negative side of an 
> acceleration :o) - before Dmitry's recent work, the sheer act 
> of importing std.regex would be slow. Dmitry, do you think you 
> could use some precompiled tables to mitigate this?

First things first sombody need to profile compiler while 
compiling this snippet.

My guesswork is that instantiating templates + generating long 
symbols is the problem.

The template system obviously needs some (re)work, I think at a 
time nobody thought templates would be that abundant in D code.

Nowdays it’s easily more templates then normal functions.

> Is your caching compiler going to help the matter?

In some distant bright future where it may be finally applied to 
instantiating templates and caching codegen but even then I’m not 
100% positive.

Finally, I repeat - we have not yet identified problem. What 
takes time in the compiler needs to be figured out by disecting 
the time taken via profiler and experimentation.


—
Dmitry Olshansky