Switch to C++20 as a minimum requirement (#1086)

* Use C++20

* Fix modernize-use-constraints

* Update CI and oldest docker image

* Workaround nvcc issues

Author: tpadioleau

.clang-format

@@ -250,7 +250,7 @@ SpacesInParensOptions:
   InEmptyParentheses: false
   Other: false
 SpacesInSquareBrackets: false
-Standard: c++17
+Standard: c++20
 StatementAttributeLikeMacros:
   - Q_EMIT
 StatementMacros:

.clang-tidy

@@ -48,6 +48,7 @@ Checks: >
   modernize-*,
   -modernize-pass-by-value,
   -modernize-use-auto,
+  -modernize-use-integer-sign-comparison,
   -modernize-use-nodiscard,
   -modernize-use-trailing-return-type,
   performance-*,

.github/workflows/tests-macos.yaml

@@ -113,9 +113,7 @@ jobs:
           path: ginkgo
       - name: Install Ginkgo
         run: |
-          # Ginkgo 1.8 needs the flags "-undefined dynamic_lookup" to link, recent versions should not need it
           cmake \
-            -D CMAKE_SHARED_LINKER_FLAGS="-undefined dynamic_lookup" \
             -D GINKGO_BUILD_BENCHMARKS=OFF \
             -D GINKGO_BUILD_EXAMPLES=OFF \
             -D GINKGO_BUILD_MPI=OFF \

.github/workflows/tests-ubuntu.yaml

@@ -127,7 +127,7 @@ jobs:
           - name: 'cpu'
             c_compiler: 'gcc'
             cxx_compiler: 'g++'
-        cxx_version: ['17']
+        cxx_version: ['20']
         cmake_build_type: ['None']
     runs-on: ubuntu-latest
     needs: [docker-build, id_repo]
@@ -224,18 +224,14 @@ jobs:
             cxx_compiler: 'hipcc'
             ddc_extra_cxx_flags: ''
             kokkos_extra_cmake_flags: '-D Kokkos_ENABLE_HIP=ON -D Kokkos_ENABLE_HIP_RELOCATABLE_DEVICE_CODE=ON -D Kokkos_ENABLE_ROCTHRUST=OFF -D Kokkos_ARCH_AMD_GFX90A=ON'
-        cxx_version: ['17', '20', '23']
+        cxx_version: ['20', '23']
         build_type:
           - cmake_build_type: 'Release'
             cxx_flags: ''
           - cmake_build_type: 'Debug'
             cxx_flags: '-O1'
         exclude:
-          - image: 'oldest'  # nvcc 11 only supports C++-17
-            backend:
-              name: 'cuda'
-            cxx_version: '20'
-          - image: 'oldest'  # nvcc 11 only supports C++-17
+          - image: 'oldest'  # nvcc 12 only supports C++-20
             backend:
               name: 'cuda'
             cxx_version: '23'
@@ -421,7 +417,7 @@ jobs:
           - name: 'cpu'
             c_compiler: 'gcc'
             cxx_compiler: 'g++'
-        cxx_version: ['17']
+        cxx_version: ['20']
         cmake_build_type: ['Debug']
         sanitizer: ['address', 'undefined']
     runs-on: ubuntu-latest
@@ -522,7 +518,7 @@ jobs:
           - name: 'cpu'
             c_compiler: 'clang-21'
             cxx_compiler: 'clang++-21'
-        cxx_version: ['17']
+        cxx_version: ['20']
         cmake_build_type: ['Release']
     runs-on: ubuntu-latest
     needs: [docker-build, id_repo]

CMakeLists.txt

@@ -126,7 +126,7 @@ endif()
 add_library(ddc_core)
 add_library(DDC::core ALIAS ddc_core)
 configure_file(cmake/config.hpp.in generated/ddc/config.hpp NO_SOURCE_PERMISSIONS @ONLY)
-target_compile_features(ddc_core PUBLIC cxx_std_17)
+target_compile_features(ddc_core PUBLIC cxx_std_20)
 target_link_libraries(ddc_core PUBLIC Kokkos::kokkos)
 target_sources(
     ddc_core
@@ -145,7 +145,6 @@ target_sources(
                 src/ddc/detail/macros.hpp
                 src/ddc/detail/tagged_vector.hpp
                 src/ddc/detail/type_seq.hpp
-                src/ddc/detail/type_traits.hpp
                 src/ddc/detail/utils.hpp
                 src/ddc/aligned_allocator.hpp
                 src/ddc/chunk.hpp
@@ -219,7 +218,7 @@ if("${DDC_BUILD_KERNELS_FFT}")
 
     add_library(ddc_fft)
     add_library(DDC::fft ALIAS ddc_fft)
-    target_compile_features(ddc_fft PUBLIC cxx_std_17)
+    target_compile_features(ddc_fft PUBLIC cxx_std_20)
     target_link_libraries(ddc_fft PUBLIC DDC::core Kokkos::kokkos KokkosFFT::fft)
     target_sources(
         ddc_fft
@@ -269,7 +268,7 @@ if("${DDC_BUILD_KERNELS_SPLINES}")
 
     add_library(ddc_splines)
     add_library(DDC::splines ALIAS ddc_splines)
-    target_compile_features(ddc_splines INTERFACE cxx_std_17)
+    target_compile_features(ddc_splines INTERFACE cxx_std_20)
     target_link_libraries(
         ddc_splines
         INTERFACE DDC::core
@@ -342,7 +341,7 @@ if("${DDC_BUILD_PDI_WRAPPER}")
 
     add_library(ddc_pdi)
     add_library(DDC::pdi ALIAS ddc_pdi)
-    target_compile_features(ddc_pdi PUBLIC cxx_std_17)
+    target_compile_features(ddc_pdi PUBLIC cxx_std_20)
     target_link_libraries(ddc_pdi PUBLIC DDC::core PDI::PDI_C)
     target_sources(
         ddc_pdi

README.md

@@ -38,7 +38,7 @@ If you want to know more, join un on [Slack](https://ddc-lib.slack.com/join/shar
 
 To use DDC core, one needs the following dependencies:
 
-* a C++17-compliant compiler
+* a C++20-compliant compiler
 * CMake 3.25
 * Kokkos 4.4...<6
 * (optional, micro benchmarking) Benchmark 1.8...<2

docker/oldest/Dockerfile

@@ -7,12 +7,12 @@ FROM ubuntu:jammy@sha256:3ba65aa20f86a0fad9df2b2c259c613df006b2e6d0bfcc8a146afb8
 LABEL "org.opencontainers.image.source"="https://github.com/CExA-project/ddc"
 
 ARG BACKEND
-ARG AMDGPU_VERSION=5.7.3
+ARG AMDGPU_VERSION=6.2.4
 ARG CMAKE_VERSION=3.25.3
-ARG CUDA_MAJOR_VERSION=11
-ARG CUDA_MINOR_VERSION=8
+ARG CUDA_MAJOR_VERSION=12
+ARG CUDA_MINOR_VERSION=2
 ARG GINKGO_VERSION=1.8.0
-ARG ROCM_VERSION=5.7.3
+ARG ROCM_VERSION=6.2.4
 
 COPY bash_run /bin/
 ENV BASH_ENV=/etc/profile
@@ -66,19 +66,20 @@ RUN chmod +x /bin/bash_run \
       apt-get install -y --no-install-recommends \
       clang \
  ;; "cuda") \
+      # libnvjitlink seems to be a missing dependency of cusparse
       apt-get install -y --no-install-recommends \
       cuda-minimal-build-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
       cuda-nvtx-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
       libcublas-dev-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
       libcufft-dev-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
       libcurand-dev-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
       libcusparse-dev-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
-      gcc-10 \
-      g++-10 \
+      libnvjitlink-${CUDA_MAJOR_VERSION}-${CUDA_MINOR_VERSION} \
  ;; "hip") \
       apt-get install -y --no-install-recommends \
       hipblas-dev${ROCM_VERSION} \
       hipfft-dev${ROCM_VERSION} \
+      hiprand-dev${ROCM_VERSION} \
       hipsparse-dev${ROCM_VERSION} \
       rocm-hip-runtime-dev${ROCM_VERSION} \
       rocrand-dev${ROCM_VERSION} \
@@ -95,9 +96,13 @@ RUN chmod +x /bin/bash_run \
     "cpu") \
       cmake -DCMAKE_BUILD_TYPE=Release -DGINKGO_BUILD_OMP=ON -DGINKGO_BUILD_TESTS=OFF -DGINKGO_BUILD_EXAMPLES=OFF -DGINKGO_BUILD_BENCHMARKS=OFF -B ginkgo/build -S ginkgo \
  ;; "cuda") \
-      cmake -DCMAKE_C_COMPILER=gcc-10 -DCMAKE_CXX_COMPILER=g++-10 -DCMAKE_CUDA_HOST_COMPILER=g++-10 -DCMAKE_BUILD_TYPE=Release -DGINKGO_CUDA_ARCHITECTURES=70 -DGINKGO_BUILD_CUDA=ON -DGINKGO_BUILD_TESTS=OFF -DGINKGO_BUILD_EXAMPLES=OFF -DGINKGO_BUILD_BENCHMARKS=OFF -B ginkgo/build -S ginkgo \
+      cmake -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DCMAKE_CUDA_HOST_COMPILER=g++ -DCMAKE_BUILD_TYPE=Release -DGINKGO_CUDA_ARCHITECTURES=70 -DGINKGO_BUILD_CUDA=ON -DGINKGO_BUILD_TESTS=OFF -DGINKGO_BUILD_EXAMPLES=OFF -DGINKGO_BUILD_BENCHMARKS=OFF -B ginkgo/build -S ginkgo \
  ;; "hip") \
-      cmake -DCMAKE_PREFIX_PATH=/opt/rocm -DCMAKE_BUILD_TYPE=Release -DCMAKE_HIP_ARCHITECTURES=gfx90a -DGINKGO_BUILD_HIP=ON -DGINKGO_BUILD_TESTS=OFF -DGINKGO_BUILD_EXAMPLES=OFF -DGINKGO_BUILD_BENCHMARKS=OFF -B ginkgo/build -S ginkgo \
+      # HIP_PATH needs to be set to avoid Ginkgo defining it (https://github.com/ginkgo-project/ginkgo/blob/develop/cmake/hip_path.cmake).
+      # The Ginkgo <1.9 heuristic does not seem to be compatible with the new HIP v6 directory layout.
+      # This makes amdclang++ fail during cmake compiler test (https://releases.llvm.org/18.1.0/tools/clang/docs/HIPSupport.html#order-of-precedence-for-hip-path)
+      export HIP_PATH=`hipconfig --path` \
+      && cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_HIP_ARCHITECTURES=gfx90a -DGINKGO_BUILD_HIP=ON -DGINKGO_BUILD_TESTS=OFF -DGINKGO_BUILD_EXAMPLES=OFF -DGINKGO_BUILD_BENCHMARKS=OFF -B ginkgo/build -S ginkgo \
  ;; esac \
  && cmake --build ginkgo/build \
  && cmake --install ginkgo/build --prefix /usr \
@@ -113,8 +118,8 @@ RUN chmod +x /bin/bash_run \
  && rm -rf /var/lib/apt/lists/* \
  && useradd -d /data -m -U ci \
  && if [ "xcuda" = "x${BACKEND}" ] \
-  ; then echo 'CUDA_GCC=gcc-10' > /etc/profile.d/ddc-cuda.sh \
-       ; echo 'CUDA_GXX=g++-10' >> /etc/profile.d/ddc-cuda.sh \
+  ; then echo 'CUDA_GCC=gcc' > /etc/profile.d/ddc-cuda.sh \
+       ; echo 'CUDA_GXX=g++' >> /etc/profile.d/ddc-cuda.sh \
  ;  fi
 
 USER ci:ci

src/ddc/chunk.hpp

@@ -6,13 +6,11 @@
 
 #include <cassert>
 #include <string>
-#include <type_traits>
 #include <utility>
 
 #include <Kokkos_Core.hpp>
 
 #include "detail/kokkos.hpp"
-#include "detail/type_traits.hpp"
 
 #include "chunk_common.hpp"
 #include "chunk_span.hpp"
@@ -166,21 +164,17 @@ class Chunk : public ChunkCommon<ElementType, SupportType, Kokkos::layout_right>
     }
 
     /// Slice out some dimensions
-    template <
-            class... QueryDDims,
-            class SFINAESupportType = SupportType,
-            std::enable_if_t<is_discrete_domain_v<SFINAESupportType>, int> = 0>
+    template <class... QueryDDims>
     auto operator[](DiscreteDomain<QueryDDims...> const& odomain) const
+        requires(is_discrete_domain_v<SupportType>)
     {
         return span_view()[odomain];
     }
 
     /// Slice out some dimensions
-    template <
-            class... QueryDDims,
-            class SFINAESupportType = SupportType,
-            std::enable_if_t<is_discrete_domain_v<SFINAESupportType>, int> = 0>
+    template <class... QueryDDims>
     auto operator[](DiscreteDomain<QueryDDims...> const& odomain)
+        requires(is_discrete_domain_v<SupportType>)
     {
         return span_view()[odomain];
     }
@@ -189,9 +183,7 @@ class Chunk : public ChunkCommon<ElementType, SupportType, Kokkos::layout_right>
      * @param delems discrete coordinates
      * @return const-reference to this element
      */
-    template <
-            class... DElems,
-            std::enable_if_t<detail::all_of_v<is_discrete_element_v<DElems>...>, int> = 0>
+    template <concepts::discrete_element... DElems>
     element_type const& operator()(DElems const&... delems) const noexcept
     {
         static_assert(
@@ -207,11 +199,9 @@ class Chunk : public ChunkCommon<ElementType, SupportType, Kokkos::layout_right>
      * @param dvects discrete vectors
      * @return reference to this element
      */
-    template <
-            class... DVects,
-            std::enable_if_t<detail::all_of_v<is_discrete_vector_v<DVects>...>, int> = 0,
-            std::enable_if_t<sizeof...(DVects) != 0, int> = 0>
+    template <concepts::discrete_vector... DVects>
     element_type const& operator()(DVects const&... dvects) const noexcept
+        requires(sizeof...(DVects) != 0)
     {
         static_assert(
                 SupportType::rank() == (0 + ... + DVects::size()),
@@ -225,9 +215,7 @@ class Chunk : public ChunkCommon<ElementType, SupportType, Kokkos::layout_right>
      * @param delems discrete coordinates
      * @return reference to this element
      */
-    template <
-            class... DElems,
-            std::enable_if_t<detail::all_of_v<is_discrete_element_v<DElems>...>, int> = 0>
+    template <concepts::discrete_element... DElems>
     element_type& operator()(DElems const&... delems) noexcept
     {
         static_assert(
@@ -243,11 +231,9 @@ class Chunk : public ChunkCommon<ElementType, SupportType, Kokkos::layout_right>
      * @param dvects discrete vectors
      * @return reference to this element
      */
-    template <
-            class... DVects,
-            std::enable_if_t<detail::all_of_v<is_discrete_vector_v<DVects>...>, int> = 0,
-            std::enable_if_t<sizeof...(DVects) != 0, int> = 0>
+    template <concepts::discrete_vector... DVects>
     element_type& operator()(DVects const&... dvects) noexcept
+        requires(sizeof...(DVects) != 0)
     {
         static_assert(
                 SupportType::rank() == (0 + ... + DVects::size()),

src/ddc/chunk_common.hpp

@@ -119,10 +119,10 @@ class ChunkCommon
     }
 
 private:
-    template <class Mapping = mapping_type>
-    static KOKKOS_FUNCTION constexpr std::
-            enable_if_t<std::is_constructible_v<Mapping, extents_type>, allocation_mdspan_type>
-            make_allocation_mdspan(ElementType* ptr, SupportType const& domain)
+    static KOKKOS_FUNCTION constexpr allocation_mdspan_type make_allocation_mdspan(
+            ElementType* ptr,
+            SupportType const& domain)
+        requires(std::is_constructible_v<mapping_type, extents_type>)
     {
         return allocation_mdspan_type(ptr, detail::array(domain.extents()));
     }
@@ -212,10 +212,7 @@ class ChunkCommon
      * @param ptr the allocation pointer to the data
      * @param domain the domain that sustains the view
      */
-    template <
-            class Mapping = mapping_type,
-            std::enable_if_t<std::is_constructible_v<Mapping, extents_type>, int> = 0>
-    KOKKOS_FUNCTION constexpr ChunkCommon(ElementType* ptr, SupportType const& domain)
+    KOKKOS_FUNCTION constexpr ChunkCommon(ElementType* ptr, SupportType const& domain) requires(std::is_constructible_v<mapping_type, extents_type>)
         : m_allocation_mdspan(make_allocation_mdspan(ptr, domain))
         , m_domain(domain)
     {