configure time error reporting for STDPAR feature and CI test

Author: Puerling

.github/workflows/builds.yml

@@ -14,6 +14,8 @@ jobs:
           - os: ubuntu-22.04
           - os: ubuntu-22.04
             parallelisation: 'openmp'
+          - os: ubuntu-22.04
+            parallelisation: 'stdpar'
     env:
       BUILD_TYPE: Release
       CMAKE_FLAGS: >
@@ -59,6 +61,17 @@ jobs:
           -DSPIRIT_USE_OPENMP=ON
           $CMAKE_FLAGS
 
+      - name: Configure with STL parallelisation
+        if: matrix.parallelisation == 'stdpar'
+        shell: bash
+        working-directory: ${{runner.workspace}}/build
+        run: >
+          cmake $GITHUB_WORKSPACE
+          $BUILD_SYSTEM_FLAG
+          -DCMAKE_BUILD_TYPE=$BUILD_TYPE
+          $CMAKE_FLAGS
+          -DSPIRIT_USE_STDPAR=ON
+
       - name: Build
         shell: bash
         working-directory: ${{runner.workspace}}/build
@@ -80,6 +93,8 @@ jobs:
             parallelisation: ''
           - os: ubuntu-24.04
             parallelisation: 'openmp'
+          - os: ubuntu-24.04
+            parallelisation: 'stdpar'
           # this build cannot be configured currently
           # - os: ubuntu-24.04
           #   parallelisation: "cuda"
@@ -190,6 +205,17 @@ jobs:
           $CMAKE_FLAGS
           -DSPIRIT_USE_OPENMP=ON
 
+      - name: Configure with STL parallelisation
+        if: matrix.parallelisation == 'stdpar'
+        shell: bash
+        working-directory: ${{runner.workspace}}/build
+        run: >
+          cmake $GITHUB_WORKSPACE
+          $BUILD_SYSTEM_FLAG
+          -DCMAKE_BUILD_TYPE=$BUILD_TYPE
+          $CMAKE_FLAGS
+          -DSPIRIT_USE_STDPAR=ON
+
       - name: Build
         shell: bash
         working-directory: ${{runner.workspace}}/build

core/CMake/FindTBB.cmake

@@ -232,14 +232,44 @@ endif()
 
 ######### TBB decisions ############################################
 if( SPIRIT_USE_STDPAR )
-    include( FindTBB )
-    if( TBB_FOUND )
-        set( SPIRIT_COMPILE_DEFINITIONS ${SPIRIT_COMPILE_DEFINITIONS} -DSPIRIT_USE_STDPAR )
-        message( STATUS ">> using TBB for parallel STL" )
+    include(CheckCXXSourceCompiles)
+    set( SOURCE_CXX17_PARALLEL_ALGORITHM "
+      #include <execution>
+      int main()
+      {
+        std::execution::seq;
+        std::execution::par;
+        std::execution::par_unseq;
+        return 0;
+      }
+    " )
+    check_cxx_source_compiles( "${SOURCE_CXX17_PARALLEL_ALGORITHM}"
+                               HAVE_BUILTIN_CXX17_PARALLEL_ALGORITHM )
+
+    if( NOT HAVE_BUILTIN_CXX17_PARALLEL_ALGORITHM )
+        # Try to find TBB module
+        find_package( TBB )
+        if( TBB_FOUND )
+            set( TBB_LIB TBB::tbb )
+            message( STATUS ">> using TBB for parallel STL" )
+        else()
+            set( TBB_LIB )
+            message( WARNING ">> TBB could not be found." )
+        endif()
+        # All of these symbols are required to use this feature.
+        # So, if this compiles even if TBB was not found it should be fine.
+        list( APPEND CMAKE_REQUIRED_LIBRARIES ${TBB_LIB} )
+        check_cxx_source_compiles( "${SOURCE_CXX17_PARALLEL_ALGORITHM}"
+                                   HAVE_TBB_CXX17_PARALLEL_ALGORITHM )
+        set( HAVE_CXX17_PARALLEL_ALGORITHM ${HAVE_TBB_CXX17_PARALLEL_ALGORITHM} )
     else()
-        message( WARNING ">> TBB could not be found." )
-        set( SPIRIT_USE_STDPAR OFF )
+        set( HAVE_CXX17_PARALLEL_ALGORITHM ${HAVE_BUILTIN_CXX17_PARALLEL_ALGORITHM} )
+    endif()
+
+    if( NOT HAVE_CXX17_PARALLEL_ALGORITHM )
+        message( FATAL_ERROR "C++17 execution policies are required for SPIRIT_USE_STDPAR=ON" )
     endif()
+    set( SPIRIT_COMPILE_DEFINITIONS ${SPIRIT_COMPILE_DEFINITIONS} -DSPIRIT_USE_STDPAR )
 endif()
 ######### TBB decisions ############################################