Make submdspan accept Kokkos::pair

core/src/View/MDSpan/Kokkos_MDSpan_Header.hpp

@@ -44,6 +44,38 @@ using std::layout_stride;
 using std::mdspan;
 }  // namespace Kokkos
 #else
+
+// Opt in for Kokkos::pair to submdspan/subview
+// submdspan does only take index_pair_like which is derived from tuple_like
+// tuple_like is an enumerated list: tuple, pair, array, complex, ranges::subrange
+
+#include <Kokkos_Pair.hpp>
+
+namespace Kokkos {
+namespace detail {
+template<class IdxT1, class IdxT2>
+constexpr auto first_of(const pair<IdxT1, IdxT2> &slice) {
+  return slice.first;
+}
+template<class IdxT1, class IdxT2, class Extents, size_t k>
+KOKKOS_INLINE_FUNCTION
+constexpr auto last_of(std::integral_constant<size_t, k>, const Extents &,
+                       const pair<IdxT1, IdxT2> &slice) {
+  return slice.second;
+}
+
+template<class T, class IndexType>
+struct index_pair_like;
+
+template <class IdxT1, class IdxT2, class IndexType>
+struct index_pair_like<Kokkos::pair<IdxT1, IdxT2>, IndexType> {
+  static constexpr bool value = std::is_convertible_v<IdxT1, IndexType> &&
+                                std::is_convertible_v<IdxT2, IndexType>;
+};
+
+}
+}
+
 #include <mdspan/mdspan.hpp>
 #endif
 

core/unit_test/default/TestDefaultDeviceDevelop.cpp

@@ -16,10 +16,13 @@
 
 #include <gtest/gtest.h>
 
+#include <Kokkos_Pair.hpp>
+
 #include <Kokkos_Core.hpp>
 
 #include <TestDefaultDeviceType_Category.hpp>
 
+
 namespace Test {
 
 TEST(defaultdevicetype, development_test) {
@@ -31,5 +34,9 @@ TEST(defaultdevicetype, development_test) {
   auto prop = Kokkos::view_alloc("C");
   Kokkos::View<float*, Kokkos::LayoutRight> c(prop, Kokkos::LayoutRight(5));
   Kokkos::View<int*> b_um(b.data(), 5);
+  Kokkos::mdspan<int, Kokkos::dextents<int, 1>> mds(b.data(), 5);
+  auto sub_a = Kokkos::submdspan(mds, std::pair{1,3}); 
+  auto sub_b = Kokkos::submdspan(mds, std::array{1,3}); 
+  auto sub_c = Kokkos::submdspan(mds, Kokkos::pair{1,3}); 
 }
 }  // namespace Test

tpls/mdspan/include/experimental/__p2630_bits/submdspan_extents.hpp

@@ -17,6 +17,7 @@
 #pragma once
 
 #include <tuple>
+#include <complex>
 
 #include "strided_slice.hpp"
 namespace MDSPAN_IMPL_STANDARD_NAMESPACE {
@@ -52,6 +53,33 @@ template <class OffsetType, class ExtentType, class StrideType>
 struct is_strided_slice<
     strided_slice<OffsetType, ExtentType, StrideType>> : std::true_type {};
 
+// Helper for identifying valid pair like things
+template <class T, class IndexType> struct index_pair_like : std::false_type {};
+
+template <class IdxT1, class IdxT2, class IndexType>
+struct index_pair_like<std::pair<IdxT1, IdxT2>, IndexType> {
+  static constexpr bool value = std::is_convertible_v<IdxT1, IndexType> &&
+                                std::is_convertible_v<IdxT2, IndexType>;
+};
+
+template <class IdxT1, class IdxT2, class IndexType>
+struct index_pair_like<std::tuple<IdxT1, IdxT2>, IndexType> {
+  static constexpr bool value = std::is_convertible_v<IdxT1, IndexType> &&
+                                std::is_convertible_v<IdxT2, IndexType>;
+};
+
+template <class IdxT, class IndexType>
+struct index_pair_like<std::complex<IdxT>, IndexType> {
+  static constexpr bool value = std::is_convertible_v<IdxT, IndexType>;
+};
+
+template <class IdxT, class IndexType>
+struct index_pair_like<std::array<IdxT, 2>, IndexType> {
+  static constexpr bool value = std::is_convertible_v<IdxT, IndexType>;
+};
+
+// FIXME: we actually need to pass IndexType into all of these
+
 // first_of(slice): getting begin of slice specifier range
 MDSPAN_TEMPLATE_REQUIRES(
   class Integral,
@@ -70,7 +98,7 @@ first_of(const ::MDSPAN_IMPL_STANDARD_NAMESPACE::full_extent_t &) {
 
 MDSPAN_TEMPLATE_REQUIRES(
   class Slice,
-  /* requires */(std::is_convertible_v<Slice, std::tuple<size_t, size_t>>)
+  /* requires */(index_pair_like<Slice, size_t>::value)
 )
 MDSPAN_INLINE_FUNCTION
 constexpr auto first_of(const Slice &i) {
@@ -100,7 +128,7 @@ constexpr Integral
 
 MDSPAN_TEMPLATE_REQUIRES(
   size_t k, class Extents, class Slice,
-  /* requires */(std::is_convertible_v<Slice, std::tuple<size_t, size_t>>)
+  /* requires */(index_pair_like<Slice, size_t>::value)
 )
 MDSPAN_INLINE_FUNCTION
 constexpr auto last_of(std::integral_constant<size_t, k>, const Extents &,

tpls/mdspan/include/experimental/__p2630_bits/submdspan_mapping.hpp

@@ -98,8 +98,7 @@ template<class SliceSpecifier, class IndexType>
 struct is_range_slice {
   constexpr static bool value =
     std::is_same_v<SliceSpecifier, full_extent_t> ||
-    std::is_convertible_v<SliceSpecifier,
-                          std::tuple<IndexType, IndexType>>;
+    index_pair_like<SliceSpecifier, IndexType>::value;
 };
 
 template<class SliceSpecifier, class IndexType>