[CMake] VS2012 builds using v3.1.0 are a lot slower than v2.8.12

[Brad King]

On 01/17/2015 12:20 PM, Yves Frederix wrote:
> I also tested with the build of an 'open' project (the crypto example
> was part of a work-related project). The results below are for the
> compilation of OpenCV (latest git from
> https://github.com/itseez/opencv), again with VS2012 Win64, Release
> only and no tweaking of the CMake settings.
> 
> 3.1.0:    10m50s
> 2.8.12:   4m02s
> 3.1.0 (/MP): 6m29s
> 2.8.12 (/MP): 3m48s

I cannot reproduce that.  On my machine for OpenCV (as of commit
5e92a777) I get about the same time for either version of CMake.

 3.1.0         : 8m57s
 2.8.12.2      : 8m58s
 3.1.0    (/MP): 4m52s
 2.8.12.2 (/MP): 4m57s

Check in your cases that 3.1.0 does not activate additional parts of
the project that are not built under 2.8.12.

Also please try a command-line build with just "msbuild" instead of
going through "cmake --build":

 msbuild ALL_BUILD.vcxproj /p:Configuration=Release /p:VisualStudioVersion=12.0

That will take one more layer out of the test cases.

-Brad