On Thursday, 25 July 2013 at 19:07:02 UTC, Walter Bright wrote:
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.
Obstacks are a popular approach in compilers. Allocation is the
simple pointer-bump, so it should maintain the new speed.
Deallocation can be done blockwise. Works great, if you know the
lifetime of the objects.
