Remove mdspan support

CMakeLists.txt

@@ -6,18 +6,11 @@ project(KokkosComm VERSION 0.0.2)
 
 option(KokkosComm_ENABLE_PERFTESTS "Build KokkosComm perf tests" ON)
 option(KokkosComm_ENABLE_TESTS "Build KokkosComm perf tests" ON)
-option(KokkosComm_ENABLE_MDSPAN "Build mdspan overloads" OFF)
-option(KokkosComm_MDSPAN_IMPL "mdspan implementation to use [std, kokkos]" "kokkos")
-option(KokkosComm_USE_STD_MDSPAN "Use std::mdspan (requires c++23)" OFF)
-option(KokkosComm_USE_KOKKOS_MDSPAN "Use Kokkos mdspan implementation" OFF)
 
 
 ## resolve options
 set(KOKKOSCOMM_ENABLE_PERFTESTS ${KokkosComm_ENABLE_PERFTESTS} CACHE BOOL "" FORCE)
 set(KOKKOSCOMM_ENABLE_TESTS ${KokkosComm_ENABLE_TESTS} CACHE BOOL "" FORCE)
-set(KOKKOSCOMM_ENABLE_MDSPAN ${KokkosComm_ENABLE_MDSPAN} CACHE BOOL "" FORCE)
-set(KOKKOSCOMM_USE_KOKKOS_MDSPAN ${KokkosComm_USE_KOKKOS_MDSPAN} CACHE BOOL "" FORCE)
-set(KOKKOSCOMM_USE_STD_MDSPAN ${KokkosComm_USE_STD_MDSPAN} CACHE BOOL "" FORCE)
 
 find_package(Kokkos REQUIRED)
 find_package(MPI REQUIRED)
@@ -29,26 +22,6 @@ message(STATUS "Kokkos MPI: MPI_CXX_COMPILE_DEFINITIONS = ${MPI_CXX_COMPILE_DEFI
 message(STATUS "Kokkos MPI: MPI_CXX_INCLUDE_DIRS =        ${MPI_CXX_INCLUDE_DIRS}")
 message(STATUS "Kokkos MPI: MPI_CXX_LINK_FLAGS =          ${MPI_CXX_LINK_FLAGS}")
 message(STATUS "Kokkos MPI: MPI_CXX_LIBRARIES =           ${MPI_CXX_LIBRARIES}")
-if (KOKKOSCOMM_ENABLE_MDSPAN)
-    if (KOKKOSCOMM_USE_STD_MDSPAN)
-        message(STATUS "Kokkos MPI: mdspan support enabled (std::mdspan)")
-    elseif(KOKKOSCOMM_USE_KOKKOS_MDSPAN)
-        message(STATUS "Kokkos MPI: mdspan support enabled (kokkos/mdspan)")
-    else()
-        message(FATAL_ERROR "Kokkos MPI: mdspan support enabled but no MDSPAN implementation enabled!")
-    endif()
-endif()
-
-include(FetchContent)
-if(KOKKOSCOMM_ENABLE_MDSPAN AND KOKKOSCOMM_USE_KOKKOS_MDSPAN)
-    message(STATUS "retrieving kokkos/mdspan...")
-    FetchContent_Declare(
-        kokkos_mdspan
-        GIT_REPOSITORY https://github.com/kokkos/mdspan.git
-        GIT_TAG        9ceface91483775a6c74d06ebf717bbb2768452f # mdspan-0.6.0
-        )
-    FetchContent_MakeAvailable(kokkos_mdspan)
-endif()
 
 
 include(cmake/flags.cmake)
@@ -126,4 +99,4 @@ endif()
 if(KOKKOSCOMM_ENABLE_PERFTESTS)
     enable_testing()
     add_subdirectory(perf_tests)
-endif()
+endif()

cmake/flags.cmake

@@ -59,24 +59,8 @@ function(kokkoscomm_add_cxx_flags)
         target_compile_options(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_OPTIONS_KEYWORD} $<BUILD_INTERFACE:-Wno-gnu-zero-variadic-macro-arguments>)
     endif()
 
-    # mdspan-related definitions
-    if (KOKKOSCOMM_ENABLE_MDSPAN)
-        target_compile_definitions(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_OPTIONS_KEYWORD} KOKKOSCOMM_ENABLE_MDSPAN)
-        if(KOKKOSCOMM_USE_STD_MDSPAN)
-            target_compile_definitions(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_OPTIONS_KEYWORD} KOKKOSCOMM_USE_STD_MDSPAN)
-        elseif(KOKKOSCOMM_USE_KOKKOS_MDSPAN)
-            target_compile_definitions(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_OPTIONS_KEYWORD} KOKKOSCOMM_USE_KOKKOS_MDSPAN)
-            target_compile_definitions(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_OPTIONS_KEYWORD} KOKKOSCOMM_MDSPAN_IN_EXPERIMENTAL)
-        endif()
-    endif()      
-
     # choose cxx standard
     set_target_properties(${ADD_CXX_FLAGS_TARGET} PROPERTIES CXX_EXTENSIONS OFF)
-    if (KOKKOSCOMM_ENABLE_MDSPAN AND KOKKOSCOMM_USE_STD_MDSPAN)
-        target_compile_features(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_FEATURES_KEYWORD} cxx_std_23)
-    else()
-        target_compile_features(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_FEATURES_KEYWORD} cxx_std_20)
-    endif()
-
+    target_compile_features(${ADD_CXX_FLAGS_TARGET} ${TARGET_COMPILE_FEATURES_KEYWORD} cxx_std_20)
 
-endfunction()
+endfunction()

docs/api/core.rst

@@ -8,7 +8,6 @@ Core
     * - MPI
       - ``KokkosComm::``
       - ``Kokkos::View``
-      - mdspan
     * - MPI_Send
       - send
       - ✓
@@ -29,7 +28,7 @@ Core
 Point-to-point
 --------------
 
-.. cpp:function:: template <KokkosExecutionSpace ExecSpace, ViewOrMdspan SendView> \
+.. cpp:function:: template <KokkosExecutionSpace ExecSpace, KokkosView SendView> \
                   Req KokkosComm::isend(const ExecSpace &space, const SendView &sv, int dest, int tag, MPI_Comm comm)
 
     MPI_Isend wrapper
@@ -43,7 +42,7 @@ Point-to-point
     :tparam ExecSpace: A Kokkos execution space to operate in
     :returns: A KokkosComm::Req representing the asynchronous communication and any lifetime-extended views.
 
-.. cpp:function:: template <KokkosExecutionSpace ExecSpace, ViewOrMdspan SendView> \
+.. cpp:function:: template <KokkosExecutionSpace ExecSpace, KokkosView SendView> \
                   void KokkosComm::send(const ExecSpace &space, const SendView &sv, int dest, int tag, MPI_Comm comm)
 
     MPI_Send wrapper
@@ -56,7 +55,7 @@ Point-to-point
     :tparam SendView: A Kokkos::View to send
     :tparam ExecSpace: A Kokkos execution space to operate in
 
-.. cpp:function:: template <KokkosExecutionSpace ExecSpace, ViewOrMdspan RecvView> \
+.. cpp:function:: template <KokkosExecutionSpace ExecSpace, KokkosView RecvView> \
                   void KokkosComm::recv(const ExecSpace &space, RecvView &rv, int src, int tag, MPI_Comm comm)
 
     MPI_Recv wrapper
@@ -73,7 +72,7 @@ Point-to-point
 Collective
 ----------
 
-.. cpp:function:: template <KokkosExecutionSpace ExecSpace, ViewOrMdspan SendView, ViewOrMdspan RecvView> \
+.. cpp:function:: template <KokkosExecutionSpace ExecSpace, KokkosView SendView, KokkosView RecvView> \
                   void KokkosComm::reduce(const ExecSpace &space, const SendView &sv, const RecvView &rv, MPI_Op op, int root, MPI_Comm comm)
 
     MPI_Reduce wrapper
@@ -107,4 +106,4 @@ Related Types
                       void KokkosComm::Req::keep_until_wait(const View &v)
 
         Extend the lifetime of v at least until Req::wait() is called.
-        This is useful to prevent a View from being destroyed during an asynchronous MPI operation.
+        This is useful to prevent a View from being destroyed during an asynchronous MPI operation.

docs/api/traits.rst

@@ -7,7 +7,7 @@ Basic Traits
 .. cpp:type:: template<typename View> \
               KokkosComm::Traits
 
-    A common interface to access Kokkos::View- and std::mdspan-like types.
+    A common interface to access Kokkos::View-like types.
 
     .. cpp:function:: static bool is_contiguous(const View &v)
 
@@ -41,7 +41,7 @@ Strategies for handling non-contiguous views
 .. cpp:type:: template<typename View> \
               KokkosComm::PackTraits
 
-    A common packing-related interface for Kokkos::View- and std::mdspan-like types.
+    A common packing-related interface for Kokkos::View-like types.
 
   .. cpp:type:: packer_type
 
@@ -53,4 +53,4 @@ Strategies for handling non-contiguous views
 
   .. cpp:function:: static bool needs_pack(const View &v)
 
-    :returns: true iff ``View`` ``v`` needs to be unpacked after being passed from MPI
+    :returns: true iff ``View`` ``v`` needs to be unpacked after being passed from MPI

docs/design.rst

@@ -9,7 +9,6 @@ Asynchronous MPI operations and view lifetimes
 Non-contiguous Data
 -------------------
 
-- Packer::MpiDatatype which just constructs an MPI Datatype matching the mdspan and hands it off to MPI to deal with the non-contiguous data
 - Packer::DeepCopy uses `Kokkos::deep_copy` to handle packing and unpacking of non-contiguous `Kokkos::View`. This requires an intermediate allocation, which only works for Kokkos Views, see `Device Data`_.
 
 Device Data
@@ -18,6 +17,3 @@ Device Data
 Contiguous device data is handed to MPI as-is.
 
 For non-contiguous Kokkos::Views in a non-``Kokkos::HostSpace``, any temporary buffers are allocated in the same memory space as the view being operated on.
-
-For non-contiguous mdspan, there is no standards-compliant way to get an allocator that can produce the same kind of allocation as the mdspan.
-In that case, the Packer::MpiDatatype packer needs to be used, where a datatype is created to describe the mdspan (without accessing any of the mdspan's data!) and then that is handed off to the MPI implementation.

docs/usage/getting_started.rst

@@ -16,29 +16,9 @@ A basic build:
 
     ctest -V --test-dir /path/to/build/directory
 
-A build with ``mdspan`` support through kokkos/mdspan.
-You need to turn on ONE of ``KokkosComm_USE_STD_MDSPAN`` or ``KokkosComm_USE_KOKKOS_MDSPAN``.
-As of March 2024, only Clang 18 has full ``std::mdspan`` support, so you will probably want ``KokkosComm_USE_KOKKOS_MDSPAN``.
-
-.. code-block:: bash
-
-    cmake -S /path/to/kokkos-comm \
-      -B /path/to/build/directory \
-      -DKokkos_ROOT=/path/to/kokkos-install/ \
-      -DKokkosComm_ENABLE_MDSPAN=ON \
-      -DKokkosComm_USE_KOKKOS_MDSPAN=ON
-
-
 Configuration Options
 ---------------------
 
-* ``KokkosComm_ENABLE_MDSPAN``: (default=OFF) build with mdspan support
-  * Causes ``KOKKOSCOMM_ENABLE_MDSPAN`` to be defined in source files
-* ``KokkosComm_USE_STD_MDSPAN``: (default=OFF) use std::mdspan as the mdspan implementation (if KokkosComm_ENABLE_MDSPAN)
-  * Causes ``KOKKOSCOMM_USE_STD_MDSPAN`` to be defined in source files
-* ``KokkosComm_USE_KOKKOS_MDSPAN``: (default=OFF) retrieve and use kokkos/mdspan as the mdspan implementation (if KokkosComm_ENABLE_MDSPAN)
-  * Causes ``KOKKOSCOMM_USE_KOKKOS_MDSPAN`` to be defined in source files
-  * Causes ``KOKKOSCOMM_MDSPAN_IN_EXPERIMENTAL`` to be defined in source files
 * ``KokkosComm_ENABLE_PERFTESTS``: (default=ON) build performance tests
 * ``KokkosComm_ENABLE_TESTS``: (default=ON) build unit tests
 

src/CMakeLists.txt

@@ -11,9 +11,6 @@ target_include_directories(KokkosComm INTERFACE
     $<INSTALL_INTERFACE:include>
 )
 target_link_libraries(KokkosComm INTERFACE MPI::MPI_CXX Kokkos::kokkos)
-if(KOKKOSCOMM_USE_KOKKOS_MDSPAN)
-  target_link_libraries(KokkosComm INTERFACE mdspan)
-endif()
 
 file(GLOB_RECURSE KOKKOSCOMM_PUBLIC_HEADERS ${CMAKE_CURRENT_LIST_DIR}/*.hpp)
-set(KOKKOSCOMM_PUBLIC_HEADERS ${KOKKOSCOMM_PUBLIC_HEADERS} PARENT_SCOPE)
+set(KOKKOSCOMM_PUBLIC_HEADERS ${KOKKOSCOMM_PUBLIC_HEADERS} PARENT_SCOPE)

src/KokkosComm.hpp

@@ -27,19 +27,19 @@
 
 namespace KokkosComm {
 
-template <KokkosExecutionSpace ExecSpace, ViewOrMdspan SendView>
+template <KokkosExecutionSpace ExecSpace, KokkosView SendView>
 Req isend(const ExecSpace &space, const SendView &sv, int dest, int tag,
           MPI_Comm comm) {
   return Impl::isend(space, sv, dest, tag, comm);
 }
 
-template <KokkosExecutionSpace ExecSpace, ViewOrMdspan SendView>
+template <KokkosExecutionSpace ExecSpace, KokkosView SendView>
 void send(const ExecSpace &space, const SendView &sv, int dest, int tag,
           MPI_Comm comm) {
   return Impl::send(space, sv, dest, tag, comm);
 }
 
-template <KokkosExecutionSpace ExecSpace, ViewOrMdspan RecvView>
+template <KokkosExecutionSpace ExecSpace, KokkosView RecvView>
 void recv(const ExecSpace &space, RecvView &sv, int src, int tag,
           MPI_Comm comm) {
   return Impl::recv(space, sv, src, tag, comm);

src/KokkosComm_collective.hpp

@@ -23,7 +23,7 @@
 
 namespace KokkosComm {
 
-template <ViewOrMdspan SendView, ViewOrMdspan RecvView,
+template <KokkosView SendView, KokkosView RecvView,
           KokkosExecutionSpace ExecSpace>
 void reduce(const ExecSpace &space, const SendView &sv, const RecvView &rv,
             MPI_Op op, int root, MPI_Comm comm) {

src/KokkosComm_pack_traits.hpp

@@ -19,7 +19,6 @@
 #include "KokkosComm_traits.hpp"
 
 #include "KokkosComm_concepts.hpp"
-#include "KokkosComm_mdspan.hpp"
 #include "KokkosComm_packer.hpp"
 
 /*! \brief Defines a common interface for packing and unpacking
@@ -47,19 +46,4 @@ struct PackTraits<View> {
   }
 };
 
-#if KOKKOSCOMM_ENABLE_MDSPAN
-
-template <Mdspan Span>
-struct PackTraits<Span> {
-  using packer_type = Impl::Packer::MpiDatatype<Span>;
-
-  static bool needs_unpack(const Span &v) {
-    return !Traits<Span>::is_contiguous(v);
-  }
-  static bool needs_pack(const Span &v) {
-    return !Traits<Span>::is_contiguous(v);
-  }
-};
-
-#endif  // KOKKOSCOMM_ENABLE_MDSPAN
 }  // namespace KokkosComm