Hi,
I this time I made a quick pass through all changes, before commenting on
first commits,
and they look solid to me, and I haven't noticed anything I would like to
change (except parentheses
around requires, but I will handle that locally). I will try to do a full
review during this week.
Regards,
Tomasz
On Sun, Aug 3, 2025 at 10:59 PM Luc Grosheintz <luc.groshei...@gmail.com>
wrote:
> The combined effect of this sequence of change is:
>
> * a reduction in the number of template instantiations, by
> - avoiding needless dependency of IndexType,
> - special formulas for low-rank extents,
> - special formulas for (nearly) fully dynamic extents.
>
> * improved code quality, by
> - precomputing partial products of the static extents,
> - special cases for low-rank extents,
> - rewriting the condition E[i] == dynamic_extent in a more
> optimizer friendly manner.
> - effectively loop-unrolling extents::operator==.
>
> While simplistic micro-benchmarking shows the effectiveness of these
> changes, likely the stronger argument is presented in each commit:
> a) each change removes needless complexity,
> b) before/after examples of generated code show the effectiveness.
>
> Luc Grosheintz (8):
> libstdc++: Reduce template instantiations in <mdspan>.
> libstdc++: Precompute products of static extents.
> libstdc++: Improve low-rank layout_{left,right}::stride.
> libstdc++: Improve fully dynamic extents in mdspan.
> libstdc++: Improve nearly fully dynamic extents in mdspan.
> libstdc++: Reduce indirection in extents::extent.
> libstdc++: Improve extents::operator==.
> libstdc++: Replace numeric_limit with __int_traits in mdspan.
>
> libstdc++-v3/include/std/mdspan | 282 +++++++++++++-----
> .../mdspan/extents/class_mandates_neg.cc | 3 +
> 2 files changed, 208 insertions(+), 77 deletions(-)
>
> --
> 2.50.0
>
>
