This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of New status.
simd::unchecked_scatter_to
is underconstrainedSection: 29.10.8.11 [simd.permute.memory] Status: New Submitter: Hewill Kang Opened: 2025-09-29 Last modified: 2025-10-03
Priority: Not Prioritized
View all issues with New status.
Discussion:
Both simd::unchecked_scatter_to
and simd::partial_scatter_to
are used to write a
simd::vec
into a range R
.
R
to be contiguous_range
and sized_range
.
Requiring R
to be output_range
is also necessary; otherwise, the
constant_range
cannot be written.
Proposed resolution:
This wording is relative to N5014.
Modify 29.10.3 [simd.syn] as indicated:
namespace std::simd { […] template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void unchecked_scatter_to(const V& v, R&& out, const I& indices, flags<Flags...> f = {}); template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void unchecked_scatter_to(const V& v, R&& out, const typename I::mask_type& mask, const I& indices, flags<Flags...> f = {}); template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void partial_scatter_to(const V& v, R&& out, const I& indices, flags<Flags...> f = {}); template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void partial_scatter_to(const V& v, R&& out, const typename I::mask_type& mask, const I& indices, flags<Flags...> f = {}); […] }
Modify 29.10.8.11 [simd.permute.memory] as indicated:
template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void unchecked_scatter_to(const V& v, R&& out, const I& indices, flags<Flags...> f = {}); template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void unchecked_scatter_to(const V& v, R&& out, const typename I::mask_type& mask, const I& indices, flags<Flags...> f = {});-10- Let
[…]mask
betypename I::mask_type(true)
for the overload with nomask
parameter.template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void partial_scatter_to(const V& v, R&& out, const I& indices, flags<Flags...> f = {}); template<simd-vec-type V, ranges::contiguous_range R, simd-integral I, class... Flags> requires ranges::sized_range<R> && ranges::output_range<R, typename V::value_type> constexpr void partial_scatter_to(const V& v, R&& out, const typename I::mask_type& mask, const I& indices, flags<Flags...> f = {});-13- Let
[…]mask
betypename I::mask_type(true)
for the overload with nomask
parameter.