New submdspan CPP 17 compatible

CMakeLists.txt

@@ -171,7 +171,11 @@ if(MDSPAN_ENABLE_EXAMPLES)
 endif()
 
 if(MDSPAN_ENABLE_BENCHMARKS)
-  add_subdirectory(benchmarks)
+  if(NOT MDSPAN_CXX_STANDARD STREQUAL "14")
+    add_subdirectory(benchmarks)
+  else()
+    MESSAGE(FATAL_ERROR "Benchmarks are not available in C++14 mode. Turn MDSPAN_ENABLE_BENCHMARKS OFF or use C++17 or newer.")
+  endif()
 endif()
 
 if(MDSPAN_ENABLE_COMP_BENCH)

README.md

@@ -69,6 +69,8 @@ When not in C++23 mode the implementation deviates from the proposal as follows:
 
 ### C++14
 - deduction guides don't exist
+- submdspan (P2630) is not available - an earlier variant of submdspan is available up to release 0.5 in C++14 mode
+- benchmarks are not available (they need submdspan)
 
 
 

compilation_tests/CMakeLists.txt

@@ -20,5 +20,7 @@ if(NOT MDSPAN_ENABLE_CUDA)
   add_compilation_test(ctest_compressed_pair_layout)
 endif()
 add_compilation_test(ctest_constexpr_dereference)
+if(NOT CMAKE_CXX_STANDARD STREQUAL "14")
 add_compilation_test(ctest_constexpr_submdspan)
+endif()
 add_compilation_test(ctest_constexpr_layouts)

include/experimental/__p2630_bits/strided_index_range.hpp

@@ -0,0 +1,34 @@
+
+//@HEADER
+// ************************************************************************
+//
+//                        Kokkos v. 4.0
+//       Copyright (2022) National Technology & Engineering
+//               Solutions of Sandia, LLC (NTESS).
+//
+// Under the terms of Contract DE-NA0003525 with NTESS,
+// the U.S. Government retains certain rights in this software.
+//
+// Part of Kokkos, under the Apache License v2.0 with LLVM Exceptions.
+// See https://kokkos.org/LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//@HEADER
+
+namespace std {
+namespace experimental {
+
+// Slice Specifier allowing for strides and compile time extent
+template <class OffsetType, class ExtentType, class StrideType>
+struct strided_index_range {
+  using offset_type = OffsetType;
+  using extent_type = ExtentType;
+  using stride_type = StrideType;
+
+  OffsetType offset;
+  ExtentType extent;
+  StrideType stride;
+};
+
+} // experimental
+} // std

include/experimental/__p2630_bits/submdspan.hpp

@@ -0,0 +1,40 @@
+//@HEADER
+// ************************************************************************
+//
+//                        Kokkos v. 4.0
+//       Copyright (2022) National Technology & Engineering
+//               Solutions of Sandia, LLC (NTESS).
+//
+// Under the terms of Contract DE-NA0003525 with NTESS,
+// the U.S. Government retains certain rights in this software.
+//
+// Part of Kokkos, under the Apache License v2.0 with LLVM Exceptions.
+// See https://kokkos.org/LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//@HEADER
+
+#include "submdspan_extents.hpp"
+#include "submdspan_mapping.hpp"
+
+namespace std {
+namespace experimental {
+template <class ElementType, class Extents, class LayoutPolicy,
+          class AccessorPolicy, class... SliceSpecifiers>
+MDSPAN_INLINE_FUNCTION
+constexpr auto
+submdspan(const mdspan<ElementType, Extents, LayoutPolicy, AccessorPolicy> &src,
+          SliceSpecifiers... slices) {
+  const auto sub_mapping_offset = submdspan_mapping(src.mapping(), slices...);
+  // NVCC has a problem with the deduction so lets figure out the type
+  using sub_mapping_t = std::remove_cv_t<decltype(sub_mapping_offset.mapping)>;
+  using sub_extents_t = typename sub_mapping_t::extents_type;
+  using sub_layout_t = typename sub_mapping_t::layout_type;
+  using sub_accessor_t = typename AccessorPolicy::offset_policy;
+  return mdspan<ElementType, sub_extents_t, sub_layout_t, sub_accessor_t>(
+      src.accessor().offset(src.data_handle(), sub_mapping_offset.offset),
+      sub_mapping_offset.mapping,
+      sub_accessor_t(src.accessor()));
+}
+} // namespace experimental
+} // namespace std