cmake: move kokkos to external project (part I)

cmake/2826.patch

@@ -0,0 +1,13 @@
+diff --git a/lib/kokkos/containers/src/Kokkos_ScatterView.hpp b/lib/kokkos/containers/src/Kokkos_ScatterView.hpp
+index a8c05e3..1d83aed 100644
+--- a/lib/kokkos/containers/src/Kokkos_ScatterView.hpp
++++ b/lib/kokkos/containers/src/Kokkos_ScatterView.hpp
+@@ -681,7 +681,7 @@ class ScatterView<DataType
+                    ,contribution>
+ {
+ public:
+-  typedef Kokkos::View<DataType, Layout, ExecSpace> original_view_type;
++  typedef Kokkos::View<DataType, Layout, Kokkos::Device<ExecSpace, Kokkos::Cuda::memory_space> > original_view_type;
+   typedef typename original_view_type::value_type original_value_type;
+   typedef typename original_view_type::reference_type original_reference_type;
+   friend class ScatterAccess<DataType, Op, ExecSpace, Layout, ScatterNonDuplicated, contribution, ScatterNonAtomic>;

cmake/Modules/Packages/KOKKOS.cmake

@@ -1,22 +1,38 @@
 if(PKG_KOKKOS)
-  # TODO: this option needs to be documented when this works with a
-  # regular release version of KOKKOS, and a version compatibility check
-  # of external KOKKOS lib versus what the KOKKOS package needs is required.
-  option(EXTERNAL_KOKKOS "Build against external kokkos library")
-  if(EXTERNAL_KOKKOS)
-    find_package(Kokkos REQUIRED)
-    list(APPEND LAMMPS_LINK_LIBS Kokkos::kokkos)
+  find_package(Kokkos 3 QUIET)
+  if(Kokkos_FOUND)
+    set(DOWNLOAD_KOKKOS_DEFAULT OFF)
   else()
-    set(LAMMPS_LIB_KOKKOS_SRC_DIR ${LAMMPS_LIB_SOURCE_DIR}/kokkos)
-    set(LAMMPS_LIB_KOKKOS_BIN_DIR ${LAMMPS_LIB_BINARY_DIR}/kokkos)
-    add_subdirectory(${LAMMPS_LIB_KOKKOS_SRC_DIR} ${LAMMPS_LIB_KOKKOS_BIN_DIR})
-
-    set(Kokkos_INCLUDE_DIRS ${LAMMPS_LIB_KOKKOS_SRC_DIR}/core/src
-                            ${LAMMPS_LIB_KOKKOS_SRC_DIR}/containers/src
-                            ${LAMMPS_LIB_KOKKOS_SRC_DIR}/algorithms/src
-                            ${LAMMPS_LIB_KOKKOS_BIN_DIR})
-    include_directories(${Kokkos_INCLUDE_DIRS})
-    list(APPEND LAMMPS_LINK_LIBS kokkos)
+    set(DOWNLOAD_KOKKOS_DEFAULT ON)
+  endif()
+  option(DOWNLOAD_KOKKOS "Download the KOKKOS library instead of using an already installed one" ${DOWNLOAD_KOKKOS_DEFAULT})
+  if(DOWNLOAD_KOKKOS)
+    message(STATUS "KOKKOS download requested - we will build our own")
+    # Workaround for cross compilation with MinGW where ${CMAKE_INSTALL_LIBDIR}
+    # is a full path, so we need to remove the prefix
+    string(REPLACE ${CMAKE_INSTALL_PREFIX} "" _KOKKOS_LIBDIR ${CMAKE_INSTALL_LIBDIR})
+    include(ExternalProject)
+    ExternalProject_Add(kokkos_build
+      URL https://github.com/kokkos/kokkos/archive/3.0.00.tar.gz
+      URL_MD5 281c7093aa3a603276e93abdf4be23b9
+      PATCH_COMMAND patch -p3 < ${CMAKE_CURRENT_SOURCE_DIR}/2826.patch
+      CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR> ${CMAKE_REQUEST_PIC}
+      -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
+      -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM} -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}
+      BUILD_BYPRODUCTS <INSTALL_DIR>/${_KOKKOS_LIBDIR}/libkokkoscore.a
+    )
+    list(APPEND LAMMPS_DEPS kokkos_build)
+    ExternalProject_get_property(kokkos_build INSTALL_DIR)
+    set(KOKKOS_LIBRARIES ${INSTALL_DIR}/${_KOKKOS_LIBDIR}/libkokkoscore.a) 
+    set(KOKKOS_INCLUDE_DIRS ${INSTALL_DIR}/include)
+    include_directories(${KOKKOS_INCLUDE_DIRS})
+    list(APPEND LAMMPS_LINK_LIBS ${KOKKOS_LIBRARIES})
+  else()
+    find_package(Kokkos 3)
+    if(NOT Kokkos_FOUND)
+      message(FATAL_ERROR "KOKKOS library not found, help CMake to find it by setting KOKKOS_LIBRARY, or set DOWNLOAD_KOKKOS=ON to download it")
+    endif()
+    list(APPEND LAMMPS_LINK_LIBS Kokkos::kokkos)
   endif()
   add_definitions(-DLMP_KOKKOS)