• Andrew Godfrey (20/20) Feb 10 2016 I just upgraded from DMD 2.065.0 (so about 2 years old) to
• Joakim (4/13) Feb 10 2016 I don't think it's unexpected, though something to work on
• Andrea Fontana (4/12) Feb 11 2016 Check this:
• Ola Fosheim =?UTF-8?B?R3LDuHN0YWQ=?= (4/6) Feb 11 2016 Cool, why did the peak heap size during compilation drop from
• Andrea Fontana (4/10) Feb 11 2016 Zooming on graph you can see that the improvement was due to this:
• Ola Fosheim =?UTF-8?B?R3LDuHN0YWQ=?= (3/6) Feb 11 2016 But why? Is it using the GC, or what?
• Chris Wright (18/23) Feb 11 2016 From dmd/src/mars.d:
• Andrew Godfrey (3/5) Feb 11 2016 Very nice!

Andrew Godfrey <X y.com> writes:

I just upgraded from DMD 2.065.0 (so about 2 years old) to 
2.070.0, and noticed a difference in compilation speed. I'll 
detail what I see, in case it's interesting, but really I just 
want to ask: What should I expect? I know that DMD is now 
selfhosting, and I know there's a tradeoff between compilation 
speed and speed of generated code. Or maybe it's just a tweak to 
default compiler options.
So maybe this is completely known.

What I see:
DMD 32 running on Windows 10, on my laptop that's quite a few 
years old.
Random tiny single-file .d program; I'm looking at what happens 
when I make a change and then run the program (with or without 
"-unittest").

On 2.065.0: This takes around 1.9 seconds. On 2.070.0: This takes 
around 3.6 seconds.

I really don't want to trigger an investigation if this is just 
an anomaly - I'm still quite happy with 4 seconds to compile and 
run unit tests. I mainly mention it in case it's an interesting 
surprise.

Joakim <dlang joakim.fea.st> writes:

On Thursday, 11 February 2016 at 05:38:54 UTC, Andrew Godfrey 
wrote:
 I just upgraded from DMD 2.065.0 (so about 2 years old) to 
 2.070.0, and noticed a difference in compilation speed. I'll 
 detail what I see, in case it's interesting, but really I just 
 want to ask: What should I expect? I know that DMD is now 
 selfhosting, and I know there's a tradeoff between compilation 
 speed and speed of generated code. Or maybe it's just a tweak 
 to default compiler options.
 So maybe this is completely known.

 [...]

I don't think it's unexpected, though something to work on 
beating back.

Andrea Fontana <nospam example.com> writes:

On Thursday, 11 February 2016 at 05:38:54 UTC, Andrew Godfrey 
wrote:
 I just upgraded from DMD 2.065.0 (so about 2 years old) to 
 2.070.0, and noticed a difference in compilation speed. I'll 
 detail what I see, in case it's interesting, but really I just 
 want to ask: What should I expect? I know that DMD is now 
 selfhosting, and I know there's a tradeoff between compilation 
 speed and speed of generated code. Or maybe it's just a tweak 
 to default compiler options.
 So maybe this is completely known.

Check this:
http://digger.k3.1azy.net/trend/

Ola Fosheim =?UTF-8?B?R3LDuHN0YWQ=?= writes:

On Thursday, 11 February 2016 at 08:37:29 UTC, Andrea Fontana 
wrote:
 Check this:
 http://digger.k3.1azy.net/trend/

Cool, why did the peak heap size during compilation drop from 
approx. 180MB to 30MB?

Andrea Fontana <nospam example.com> writes:

On Thursday, 11 February 2016 at 08:46:19 UTC, Ola Fosheim 
Grøstad wrote:
 On Thursday, 11 February 2016 at 08:37:29 UTC, Andrea Fontana 
 wrote:
 Check this:
 http://digger.k3.1azy.net/trend/

 Cool, why did the peak heap size during compilation drop from 
 approx. 180MB to 30MB?

Zooming on graph you can see that the improvement was due to this:
https://github.com/D-Programming-Language/dmd/pull/4923

Ola Fosheim =?UTF-8?B?R3LDuHN0YWQ=?= writes:

On Thursday, 11 February 2016 at 08:57:22 UTC, Andrea Fontana 
wrote:
 Zooming on graph you can see that the improvement was due to 
 this:
 https://github.com/D-Programming-Language/dmd/pull/4923

But why? Is it using the GC, or what?

Chris Wright <dhasenan gmail.com> writes:

On Thu, 11 Feb 2016 09:04:22 +0000, Ola Fosheim Grøstad wrote:

 On Thursday, 11 February 2016 at 08:57:22 UTC, Andrea Fontana wrote:
 Zooming on graph you can see that the improvement was due to this:
 https://github.com/D-Programming-Language/dmd/pull/4923

 
 But why? Is it using the GC, or what?

From dmd/src/mars.d:

version (GC)
{
}
else
{
  GC.disable();
}

And the compiler is still not compiled with -version=GC by default, as 
far as I can determine.

The talks I've heard suggested that DMD may hide pointers where the GC 
can't find them (a relic from the C++ days), producing crashes and memory 
corruption when the GC is enabled. So the GC was disabled for stability.

That trend of memory reduction holds for the other samples, so this is 
probably something to do with the compiler rather than, say, writefln 
changing implementation to require much less memory to compile. But I'm 
not sure what might have caused it.

Andrew Godfrey <X y.com> writes:

On Thursday, 11 February 2016 at 08:37:29 UTC, Andrea Fontana 
wrote:
 Check this:
 http://digger.k3.1azy.net/trend/

Very nice!