[R-pkg-devel] Examples with CPU time is greater than elapsed time.

[Jiaming Yuan]

Thank you for the detailed explanation, that's really helpful!

On 11/6/22 02:22, Henrik Bengtsson wrote:
> I think it's because it suggests that the package uses more than 250%
> of CPU load on average, which suggests it runs in parallel with more
> than two parallel workers, which is the upper limit in the CRAN
> Policies (https://cran.r-project.org/web/packages/policies.html);
>
> "If running a package uses multiple threads/cores it must never use
> more than two simultaneously: the check farm is a shared resource and
> will typically be running many checks simultaneously. "
>
>  From the R Internals
> (https://cran.r-project.org/doc/manuals/r-release/R-ints.html):
>
> "_R_CHECK_EXAMPLE_TIMING_CPU_TO_ELAPSED_THRESHOLD_: For checks with
> timings enabled, report examples where the ratio of CPU time to
> elapsed time exceeds this threshold (and the CPU time is at least one
> second). This can help detect the simultaneous use of multiple CPU
> cores. Default: NA."
>
> It looks like CRAN incoming sets
> _R_CHECK_EXAMPLE_TIMING_CPU_TO_ELAPSED_THRESHOLD_=2.5.
>
> If multi-threading is involved, I guess you need to make sure to limit
> it to ~2 parallel threads.
>
> /Henrik
>
> On Sat, Nov 5, 2022 at 11:10 AM Jiaming Yuan <jm.yuan using outlook.com> wrote:
>> Hi all,
>>
>> I tried to submit an update to the xgboost package but didn't pass the
>> pre-tests with the following note (solved the other one, but this one is
>> a bit confusing):
>>
>> ```
>> Flavor: r-devel-linux-x86_64-debian-gcc
>> Check: examples, Result: NOTE
>>     Examples with CPU time > 2.5 times elapsed time
>>                          user system elapsed ratio
>>     cb.gblinear.history 1.454  0.017    0.49 3.002
>>
>> ```
>>
>> I can't reproduce the note on win-builder:
>> https://win-builder.r-project.org/ as it's running on Windows but the
>> note appears on debian tests. I'm not able to reproduce it on my local
>> machine either with Ubuntu 22.04. I'm wondering what the note is trying
>> to tell me and how can I resolve it with confidence.
>>
>>
>> The full log is here:
>> https://win-builder.r-project.org/incoming_pretest/xgboost_1.7.1.1_20221104_194252/Debian/00check.log
>> .
>>
>>
>> Many thanks!
>>
>> Jiaming
>>
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