[cfe-dev] Runtime of FormatTest.MemoizationTests

[David Blaikie via cfe-dev]

Ah, I noticed a really long runtime for this only when enabling expensive
checks. Are expensive checks enabled on the buildbot you're looking into?

Specifically it wasn't llvm's expensive checks, but the glibcxx standard
library expensive checks.

I didn't debug it any further, but I'm guessing that flag might make some
standard library ops not meet the required algorithmic complexities or
otherwise add. lot of overhead.

Itd be worth looking into exactly which checks are dominating (a profile
would hopefully show it up - though possibly shrinking the test case a bit
before profiling would be good - since the overhead of profiling on top of
the 15min runtime would be quite a lot (I tried and gave up/got bored
before it finished))

On Wed., 23 Aug. 2017, 4:52 am Raphael Isemann via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hello everyone,
>
> On our CI infrastructure I noticed that nearly all the run time of the
> test suite is spent on running the FormatTest.MemoizationTests. The
> test seems to take around 15 minutes to pass which is more than all
> other tests combined. I also see that there is a comment in this test
> that states that "This test takes VERY long when memoization is
> broken." [1].
>
> I'm not sure if the test is supposed to take so long or if broken
> memoization is causing this delay. There doesn't seem to be any bug
> report open for this on bugzilla either.
>
> Anyone has the same problem on their CI infrastructure?
>
> - Raphael
>
>
> [1]
> https://github.com/llvm-mirror/clang/blob/823b3849ec3e121d0f9043dfdd6e66546bcf0907/unittests/Format/FormatTest.cpp#L3308
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