[CMake] FYI - From Ninja-build mailing list - Fwd: Proposal: restat rules

[Alexander Neundorf]

On Friday 30 September 2011, Peter Kuemmel wrote:
> > Tested cmake/ninja with Blender's cmake files, works well, and fast!
> > Single file rebuild is 0.97 sec, same on makefiles was 3.7sec.
> 
> I also have some numbers:
> 
> ----------------------------
> Building LyX (lyx.org, 676 files):
> 
> LyX has autotools and cmake as build system.
> 
> 
> 
> * cmake generated ninja files:
> 
> 1. build
> cmake -G Ninja
> time ninja
> real 1m15.862s
> 
> 2. dry run
> ninja
> real 0m0.113s
> 
> 3. rebuild one file
> touch ../trunk/src/LyX.cpp
> time ninja
> real 0m7.340s
> 
> 
> 
> * cmake generated Makefiles:
> 
> 1. build
> cmake ../trunk
> time make -j9
> real 1m19.471s
> 
> 2. dry run
> time make -j9
> real 0m1.457s
> 
> 3. rebuild one file
> touch ../trunk/src/LyX.cpp
> time make -j9
> real 0m7.952s
> 
> 
> 
> * autotools:
> 
> 1. build
> ./configure --enable-build-type=dev (maybe different to cmake
> configuration) time make -j9
> real 3m19.988s
> 
> 2. dry run
> time make -j9
> real 0m2.165s
> 
> 3. rebuild one file
> touch ../trunk/src/LyX.cpp
> time make -j9
> real 0m13.087s
> 
> 
> 
> 
> Summary:
> 
>          build    dry    rebuild
> ninja   1m15.8   0m0.1    0m07.3
> make    1m19.4   0m1.4    0m07.9
> auto    3m19.9   0m2.1    0m13.0
> 
> So only the dry run shows a huge speedup (10-20 times faster)

Not to question your numbers, but shouldn't the difference of the dryrun 
(1.3s) also be present in the rebuild ?
I mean, this should be the time ninja is faster in checking whether any file 
changed, and in the rebuild case it has to do that too, and additionally build 
one file ?

How often did you measure this, just once or multiple times ?

Alex