On Wed, May 21, 2025 at 11:53 AM Luc Grosheintz <luc.groshei...@gmail.com>
wrote:
Implements the parts of layout_left that don't depend on any of the
other layouts.
libstdc++-v3/ChangeLog:
* include/std/mdspan (layout_left): New class.
Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
libstdc++-v3/include/std/mdspan | 307 +++++++++++++++++++++++++++++++-
1 file changed, 306 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/include/std/mdspan
b/libstdc++-v3/include/std/mdspan
index e5b1b2596d9..66c9d2cffac 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -144,6 +144,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return __exts[__i]; });
}
+ static constexpr span<const size_t>
+ _S_static_extents(size_t __begin, size_t __end) noexcept
+ {
+ return {_Extents.data() + __begin, _Extents.data() + __end};
+ }
+
+ constexpr span<const _IndexType>
+ _M_dynamic_extents(size_t __begin, size_t __end) const noexcept
+ requires (_Extents.size() > 0)
+ {
+ return {_M_dyn_exts + _S_dynamic_index[__begin],
+ _M_dyn_exts + _S_dynamic_index[__end]};
+ }
+
private:
using _S_storage = __array_traits<_IndexType,
_S_rank_dynamic>::_Type;
[[no_unique_address]] _S_storage _M_dyn_exts;
@@ -160,6 +174,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
|| _Extent <= numeric_limits<_IndexType>::max();
}
+ namespace __mdspan
+ {
+ template<typename _Extents>
+ constexpr span<const size_t>
+ __static_extents(size_t __begin = 0, size_t __end =
_Extents::rank())
+ { return _Extents::_S_storage::_S_static_extents(__begin, __end); }
+
+ template<typename _Extents>
+ constexpr span<const typename _Extents::index_type>
+ __dynamic_extents(const _Extents& __exts, size_t __begin = 0,
+ size_t __end = _Extents::rank())
+ {
+ return __exts._M_exts._M_dynamic_extents(__begin, __end);
+ }
+ }
+
template<typename _IndexType, size_t... _Extents>
class extents
{
@@ -251,7 +281,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: _M_exts(span<const _OIndexType, _Nm>(__exts))
{ }
-
template<__mdspan::__valid_index_type<index_type> _OIndexType,
size_t _Nm>
requires (_Nm == rank() || _Nm == rank_dynamic())
constexpr explicit(_Nm != rank_dynamic())
@@ -276,6 +305,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
private:
+ friend span<const size_t>
+ __mdspan::__static_extents<extents>(size_t, size_t);
+
+ friend span<const index_type>
+ __mdspan::__dynamic_extents<extents>(const extents&, size_t,
size_t);
+
using _S_storage = __mdspan::_ExtentsStorage<
_IndexType, array<size_t, sizeof...(_Extents)>{_Extents...}>;
[[no_unique_address]] _S_storage _M_exts;
@@ -286,6 +321,54 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __mdspan
{
+ template<typename _Extents>
I have suggested in other e-mail, that we could pass auto const&,
and instantiatie this with reference to array that is NTTP to storage.
+ constexpr size_t
+ __static_extents_prod(size_t __begin, size_t __end)
+ {
+ auto __sta_exts = __static_extents<_Extents>(__begin, __end);
+ size_t __ret = 1;
+ for (auto __factor : __sta_exts)
+ if (__factor != dynamic_extent)
+ __ret *= __factor;
+ return __ret;
+ }
+
+ template<typename _Extents>
+ constexpr size_t
+ __dynamic_extents_prod(const _Extents& __exts, size_t __begin,
+ size_t __end)
+ {
+ auto __dyn_exts = __dynamic_extents<_Extents>(__exts, __begin,
Template parameter is uncessary, it can be deduced.
+ __end);
+ size_t __ret = 1;
+ for (auto __factor : __dyn_exts)
+ __ret *= __factor;
+ return __ret;
+ }
+
+ template<typename _Extents>
+ constexpr typename _Extents::index_type
+ __exts_prod(const _Extents& __exts, size_t __begin, size_t __end)
noexcept
+ {
+ using _IndexType = typename _Extents::index_type;
+ _IndexType __ret = 1;
+ if constexpr (_Extents::rank_dynamic() != _Extents::rank())
+ __ret = _IndexType(__static_extents_prod<_Extents>(__begin,
__end));
+ if constexpr (_Extents::rank_dynamic() > 0)
+ __ret *= __dynamic_extents_prod(__exts, __begin, __end);
I would inline the funciton here:
+ for (auto __factor : __dynamic_extents(__exts, __begin, __end))
+ __ret *= __factor;
+ return __ret;
+ }
+
+ template<typename _Extents>
+ constexpr typename _Extents::index_type
+ __fwd_prod(const _Extents& __exts, size_t __r) noexcept
+ { return __exts_prod(__exts, 0, __r); }
+
+ template<typename _Extents>
+ constexpr typename _Extents::index_type
+ __rev_prod(const _Extents& __exts, size_t __r) noexcept
+ { return __exts_prod(__exts, __r + 1, __exts.rank()); }
+
template<typename _IndexType, size_t... _Counts>
auto __build_dextents_type(integer_sequence<size_t, _Counts...>)
-> extents<_IndexType, ((void) _Counts, dynamic_extent)...>;
@@ -304,6 +387,228 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
explicit extents(_Integrals...) ->
extents<size_t, __mdspan::__dynamic_extent<_Integrals>()...>;
+ struct layout_left
+ {
+ template<typename _Extents>
+ class mapping;
+ };
+
+ namespace __mdspan
+ {
+ template<typename _Tp>
+ constexpr bool __is_extents = false;
+
+ template<typename _IndexType, size_t... _Extents>
+ constexpr bool __is_extents<extents<_IndexType, _Extents...>> =
true;
+
+ template<typename _Extents, typename... _Indices>
+ constexpr typename _Extents::index_type
+ __linear_index_left(const _Extents& __exts, _Indices... __indices)
+ {
+ using _IndexType = typename _Extents::index_type;
+ _IndexType __res = 0;
+ if constexpr (sizeof...(__indices) > 0)
+ {
+ _IndexType __mult = 1;
+ auto __update = [&, __pos = 0u](_IndexType __idx) mutable
+ {
+ __res += __idx * __mult;
+ __mult *= __exts.extent(__pos);
+ ++__pos;
+ };
+ (__update(__indices), ...);
+ }
+ return __res;
+ }
+
+ template<typename _Tp>
+ constexpr bool
+ __contains_zero(span<_Tp> __exts)
+ {
+ for (size_t __i = 0; __i < __exts.size(); ++__i)
+ if (__exts[__i] == 0)
+ return true;
+ return false;
+ }
+
+ template<typename _Extents, typename _IndexType>
+ consteval _IndexType
+ __static_quotient(_IndexType __nom =
numeric_limits<_IndexType>::max())
+ {
+ auto __sta_exts = __static_extents<_Extents>();
+ for (auto __factor : __sta_exts)
+ {
+ if (__factor != dynamic_extent)
+ __nom /= _IndexType(__factor);
+ if (__nom == 0)
+ break;
+ }
+ return __nom;
+ }
+
+ template<typename _Extents>
+ constexpr bool
+ __is_representable_extents(const _Extents& __exts)
+ {
+ using _IndexType = _Extents::index_type;
+
+ if constexpr (__contains_zero(__static_extents<_Extents>()))
+ return true;
+
+ constexpr auto __sta_quo = __static_quotient<_Extents,
_IndexType>();
+ if constexpr (_Extents::rank_dynamic() == 0)
+ return __sta_quo != 0;
+ else
+ {
+ auto __dyn_exts = __dynamic_extents(__exts);
+ if (__contains_zero(__dyn_exts))
+ return true;
+
+ if constexpr (__sta_quo == 0)
+ return false;
+ else
+ {
+ constexpr auto __dyn_rank = _Extents::rank_dynamic();
+ auto __dyn_quo = __sta_quo;
+ for (auto __factor : __dyn_exts)
+ {
+ __dyn_quo /= __factor;
+ if (__dyn_quo == 0)
+ return false;
+ }
+ return true;
+ }
+ }
+ }
+
+ template<typename _Extents, typename _IndexType>
+ concept __representable_size = _Extents::rank_dynamic() != 0
+ || __contains_zero(__static_extents<_Extents>())
+ || (__static_quotient<_Extents, _IndexType>() != 0);
+
+ template<typename _Layout, typename _Mapping>
+ concept __mapping_of =
+ is_same_v<typename _Layout::mapping<typename
_Mapping::extents_type>,
+ _Mapping>;
+
+ template<typename _Mapping>
+ concept __standardized_mapping = __mapping_of<layout_left,
_Mapping>;
+
+ template<typename M>
+ concept __mapping_like = requires
+ {
+ requires __is_extents<typename M::extents_type>;
+ { M::is_always_strided() } -> same_as<bool>;
+ { M::is_always_exhaustive() } -> same_as<bool>;
+ { M::is_always_unique() } -> same_as<bool>;
+ bool_constant<M::is_always_strided()>::value;
+ bool_constant<M::is_always_exhaustive()>::value;
+ bool_constant<M::is_always_unique()>::value;
+ };
+
+ // A tag type to create internal ctors.
+ class __internal_ctor
+ { };
+ }
+
+ template<typename _Extents>
+ class layout_left::mapping
+ {
+ public:
+ using extents_type = _Extents;
+ using index_type = typename extents_type::index_type;
+ using size_type = typename extents_type::size_type;
+ using rank_type = typename extents_type::rank_type;
+ using layout_type = layout_left;
+
+ static_assert(__mdspan::__representable_size<_Extents, index_type>,
+ "The size of extents_type must be representable as index_type");
+
+ constexpr
+ mapping() noexcept = default;
+
+ constexpr
+ mapping(const mapping&) noexcept = default;
+
+ constexpr
+ mapping(const _Extents& __extents) noexcept
+ : _M_extents(__extents)
+ {
__glibcxx_assert(__mdspan::__is_representable_extents(_M_extents)); }
+
+ template<typename _OExtents>
+ requires (is_constructible_v<extents_type, _OExtents>)
+ constexpr explicit(!is_convertible_v<_OExtents, extents_type>)
+ mapping(const mapping<_OExtents>& __other) noexcept
+ : mapping(__other.extents(), __mdspan::__internal_ctor{})
+ { }
+
+ constexpr mapping&
+ operator=(const mapping&) noexcept = default;
+
+ constexpr const _Extents&
+ extents() const noexcept { return _M_extents; }
+
+ constexpr index_type
+ required_span_size() const noexcept
+ { return __mdspan::__fwd_prod(_M_extents, extents_type::rank()); }
+
+ template<__mdspan::__valid_index_type<index_type>... _Indices>
+ requires (sizeof...(_Indices) == extents_type::rank())
+ constexpr index_type
+ operator()(_Indices... __indices) const noexcept
+ {
+ return __mdspan::__linear_index_left(
+ this->extents(), static_cast<index_type>(__indices)...);
+ }
+
+ static constexpr bool
+ is_always_unique() noexcept { return true; }
+
+ static constexpr bool
+ is_always_exhaustive() noexcept { return true; }
+
+ static constexpr bool
+ is_always_strided() noexcept { return true; }
+
+ static constexpr bool
+ is_unique() noexcept { return true; }
+
+ static constexpr bool
+ is_exhaustive() noexcept { return true; }
+
+ static constexpr bool
+ is_strided() noexcept { return true; }
+
+ constexpr index_type
+ stride(rank_type __i) const noexcept
+ requires (extents_type::rank() > 0)
+ {
+ __glibcxx_assert(__i < extents_type::rank());
+ return __mdspan::__fwd_prod(_M_extents, __i);
+ }
+
+ template<typename _OExtents>
+ requires (extents_type::rank() == _OExtents::rank())
+ friend constexpr bool
+ operator==(const mapping& __self, const mapping<_OExtents>&
__other)
+ noexcept
+ { return __self.extents() == __other.extents(); }
+
+ private:
+ template<typename _OExtents>
+ constexpr explicit
+ mapping(const _OExtents& __oexts, __mdspan::__internal_ctor)
noexcept
+ : _M_extents(extents_type(__oexts))
+ {
+ static_assert(__mdspan::__representable_size<_OExtents,
index_type>,
+ "The size of OtherExtents must be representable as
index_type");
+
__glibcxx_assert(__mdspan::__is_representable_extents(_M_extents));
+ }
+
+ public:
+ [[no_unique_address]] _Extents _M_extents;
+ };
+
_GLIBCXX_END_NAMESPACE_VERSION
}
#endif
--
2.49.0
