[cmake-developers] CMake is slow for project with hundred target and one command with large number of dependencies

[Nicolas Desprès]

On Mon, Aug 5, 2013 at 6:06 PM, Brad King <brad.king at kitware.com> wrote:

> On 08/05/2013 11:28 AM, Nicolas Desprès wrote:
> > I have just rebased my branch on top of the master and the test suite
> still pass.
> [snip]
> > I really want to have this patch in the next release
>
> I can't promise to accept it since 2.8.12 rc1 is coming out
> tomorrow or Wednesday and this topic isn't even in 'next' yet.
> This touches some pretty fundamental logic and could easily
> have a subtle behavior change so I consider it high risk.
>
I understand. I have just found an issue that is not covered by CMake's
test suite. It happens when one of the file path is empty. I will add a
test for this case tomorrow.

>
> On 07/29/2013 08:25 AM, Stephen Kelly wrote:
> > I think Brad will have to do the rest.
>
> Sorry, I stopped reading this thread assuming that it would end
> with Steve bringing the change to the topic stage at which point
> my attention would be drawn again.
>
No problem.

>
> I just fetched the large-deps-perf topic from your Github repo.
> I've never been happy with the linear search so thanks for working
> on this.  Here are a couple comments:
>
> * Please replace large_list.cmake in the test with use of the
>   foreach() command's RANGE signature and list(APPEND).
>
Done.

>
> * Why is special logic in Tests/CMakeLists.txt needed to add
>   the test case?
>
Since it is a performance test on configuration phase only, I need a
specific timeout value and to run cmake only (neither make, nor any extra
program built the test project). I have added a comment saying so.

>
> * Please add comments explaining in prose what the lookup map
>   comparison functor is doing and why.  I could infer it only
>   by looking at the old code (which should have been commented
>   before too).  The assert examples are good for verification
>   but not for understanding from scratch.
>
I added the comment. I hope it is understandable. The best would be to have
a unit test for this method but I can't think of a simple way to do it
since there will be too many objects to mock.

I have pushed a bunch of fixup commit if you want to review them. I will
squash them tomorrow.

Thanks,

-- 
Nicolas Desprès
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