Article: Increasing the D Compiler Speed by Over 75%

[Walter Bright]

On 7/25/2013 11:30 AM, Adam D. Ruppe wrote:
> The biggest compile time killer in my experience is actually running out of
> memory and hitting the swap.
>
> My work app used to compile in about 8 seconds (on Linux btw). Then we added
> more and more stuff and it went up to about 20 seconds. It uses a fair amount of
> CTFE and template stuff, looping over almost every function in the program to
> generate code.
>
> Annoying... but then we added a little bit more and it skyrocketed to about 90
> seconds to compile! That's unbearable.
>
> The cause was the build machine had run out of physical memory at the peak of
> the compile process, and started furiously swapping to disk.
>
> I "fixed" it by convincing them to buy more RAM, and now we're back to ~15
> second compiles, but at some point the compiler will have to address this. I
> know donc has a dmd fork where he's doing a lot of work, completely
> re-engineering CTFE, so it is coming, but that will probably be the next speed
> increase, and we could be looking at as much as 5x in cases like mine!

I know the memory consumption is a problem, but it's much harder to fix.


> BTW apparently a dmd built with Microsoft's compile does the nasty in about 11
> seconds rather than 30 for the std.algorithm build - comparable to the linux
> version with gcc. I really like dmc too, but a 3x speed increase is really
> significant for something that's relatively easy to do.

An interesting project would be to research the specific cause of the difference.