[R-pkg-devel] NOTE: Installation took CPU time 3.5 times elapsed time

[Ivan Krylov]

Dear Dirk,

On Mon, 28 Jul 2025 06:45:06 -0500
Dirk Eddelbuettel <edd using debian.org> wrote:

> And I just validated it: removing that last line from DESCRIPTION
> removes the compilation time NOTE.

This must be the culprit. The 00install.out file [1] shows -flto=8 being
used, which GCC documentation [2] describes as "use 8 threads for LTO":

>> If you specify the optional n [in -flto=n], the optimization and
>> code generation done at link time is executed in parallel using n
>> parallel jobs by utilizing an installed make program. The
>> environment variable MAKE may be used to override the program used. 

I think this was set in the Makeconf on the machine running the
"gcc-san" special checks; I don't see anything in the package that
would set 8 threads in particular. R itself, when configured with
--enable-lto, only sets -flto, not -flto=8.

-- 
Best regards,
Ivan

[1]
https://win-builder.r-project.org/incoming_pretest/boostmath_1.0.1_20250727_090857/specialChecks/gcc-san/package/00install.out

[2]
https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto