Based on a post I saw here I thought it would be fun to see how
much I could speed up compilation just by using per-file makefiles
I decided to use DCD(server only) as the test bench, as it's
slightly big with all of its dependencies and takes a medium
amount of time to build. Plus it already uses make, a prime
candidate.
I hacked in another rule quickly to compile by file(just used
LDC's -od & -op flags, took about a minute), and got some
surprising results that I thought might interest someone here.
BTW, I use a 6 core CPU on my home computer. The usage seemed to
drop off a cliff at ~450% CPU though so a strong intel CPU would
may have had LDC go past DMD.
LDC baseline w/ optimization: 15.402 seconds
LDC baseline no optimization: 8.018 seconds
DMD w/ optimizations: 14.174 seconds
DMD no optimizations: 3.179 seconds
LDC -j6 w/ optimization: 7.708 seconds
LDC -j6 no optimization: 5.210 seconds
Weirdly, it also seemed to run faster.
LDC baseline:
./bin/dcd-server -I /usr/include/dlang/dmd
...
[info ] 49562 symbols cached.
[info ] Startup completed in 776.922 milliseconds.
LDC -j6:
./bin/dcd-server -I /usr/include/dlang/dmd
...
[info ] 49562 symbols cached.
[info ] Startup completed in 744.215 milliseconds.
Wasn't a random occurrence, consistently about 30-40ms shorter
with the parallel version vs baseline, same flags(except for
output flags.)
P.S., I actually got worse performance on DMD by trying this. I
think I remember reading walter say something about DMD being
optimized for throwing every file at it at once. Although, this
does enable incremental builds.
