[ENH] refactor of parallel hdf5 detection

Author: dutta-alankar

CMakeLists.txt

@@ -42,6 +42,7 @@ include(ReplaceIdefixSource)
 include(AddIdefixSource)
 include(SetIdefixProperty)
 include(SetRequiredBuildSettingsForGCC8)
+include(CheckHdf5ParallelSupport)
 
 #Idefix requires Cuda Lambdas (experimental)
 if(Kokkos_ENABLE_CUDA)
@@ -130,55 +131,8 @@ if(Idefix_HDF5)
   message(STATUS "Found HDF5 include directories: ${HDF5_INCLUDE_DIRS}")
   target_include_directories(idefix PUBLIC "${HDF5_INCLUDE_DIRS}")
   if(Idefix_MPI)
-    include(CheckCSourceCompiles)
-
-    # Some CMake/HDF5 combinations do not reliably set HDF5_IS_PARALLEL
-    # (e.g. when HDF5 is found via its CMake config package rather than the
-    # FindHDF5 module). Combine metadata checks with a compile+link probe for
-    # the MPI-IO symbols to reliably detect parallel HDF5.
-    set(_idefix_hdf5_is_parallel FALSE)
-    if(HDF5_IS_PARALLEL OR HDF5_C_IS_PARALLEL)
-      set(_idefix_hdf5_is_parallel TRUE)
-    endif()
-
-    if(NOT _idefix_hdf5_is_parallel AND DEFINED HDF5_C_COMPILER_EXECUTABLE)
-      execute_process(
-        COMMAND "${HDF5_C_COMPILER_EXECUTABLE}" -showconfig
-        OUTPUT_VARIABLE _idefix_hdf5_showconfig
-        ERROR_QUIET
-      )
-      if(_idefix_hdf5_showconfig MATCHES "Parallel HDF5:[ \t]*yes")
-        set(_idefix_hdf5_is_parallel TRUE)
-      endif()
-    endif()
-
-    set(_idefix_saved_required_includes "${CMAKE_REQUIRED_INCLUDES}")
-    set(_idefix_saved_required_libraries "${CMAKE_REQUIRED_LIBRARIES}")
-
-    set(CMAKE_REQUIRED_INCLUDES ${HDF5_INCLUDE_DIRS} ${MPI_C_INCLUDE_DIRS})
-    set(CMAKE_REQUIRED_LIBRARIES ${_idefix_hdf5_link_items} MPI::MPI_C)
-    check_c_source_compiles(
-      "#include <mpi.h>
-       #include <hdf5.h>
-       int main(void) {
-         hid_t plist = H5Pcreate(H5P_FILE_ACCESS);
-         H5Pset_fapl_mpio(plist, MPI_COMM_WORLD, MPI_INFO_NULL);
-         H5Pclose(plist);
-         return 0;
-       }"
-      IDEFIX_HDF5_HAS_MPI_IO
-    )
-
-    set(CMAKE_REQUIRED_INCLUDES "${_idefix_saved_required_includes}")
-    set(CMAKE_REQUIRED_LIBRARIES "${_idefix_saved_required_libraries}")
-    unset(_idefix_saved_required_includes)
-    unset(_idefix_saved_required_libraries)
-
-    if(IDEFIX_HDF5_HAS_MPI_IO)
-      set(_idefix_hdf5_is_parallel TRUE)
-    endif()
-
-    if(NOT _idefix_hdf5_is_parallel)
+    CheckHdf5ParallelSupport("${_idefix_hdf5_link_items}")
+    if(NOT IDEFIX_HDF5_IS_PARALLEL)
       message(FATAL_ERROR "Parallel HDF5 required for Idefix_MPI but the found HDF5 library does not support it")
     endif()
   endif()

cmake/CheckHdf5ParallelSupport.cmake

@@ -0,0 +1,50 @@
+include(CheckCSourceCompiles)
+
+# Check whether the HDF5 library found by find_package(HDF5) supports parallel
+# (MPI-IO) access, and store the result in IDEFIX_HDF5_IS_PARALLEL in the
+# caller's scope.
+#
+# Usage: CheckHdf5ParallelSupport(<hdf5_link_items>)
+# where <hdf5_link_items> is the list of HDF5 targets/libraries to link against.
+#
+# Some CMake/HDF5 combinations do not reliably set HDF5_IS_PARALLEL (e.g. when
+# HDF5 is found via its CMake config package rather than the FindHDF5 module).
+# Combine metadata checks with a compile+link probe for the MPI-IO symbols to
+# reliably detect parallel HDF5.
+function(CheckHdf5ParallelSupport hdf5_link_items)
+  set(_idefix_hdf5_is_parallel FALSE)
+  if(HDF5_IS_PARALLEL OR HDF5_C_IS_PARALLEL)
+    set(_idefix_hdf5_is_parallel TRUE)
+  endif()
+
+  if(NOT _idefix_hdf5_is_parallel AND DEFINED HDF5_C_COMPILER_EXECUTABLE)
+    execute_process(
+      COMMAND "${HDF5_C_COMPILER_EXECUTABLE}" -showconfig
+      OUTPUT_VARIABLE _idefix_hdf5_showconfig
+      ERROR_QUIET
+    )
+    if(_idefix_hdf5_showconfig MATCHES "Parallel HDF5:[ \t]*yes")
+      set(_idefix_hdf5_is_parallel TRUE)
+    endif()
+  endif()
+
+  set(CMAKE_REQUIRED_INCLUDES ${HDF5_INCLUDE_DIRS} ${MPI_C_INCLUDE_DIRS})
+  set(CMAKE_REQUIRED_LIBRARIES ${hdf5_link_items} MPI::MPI_C)
+  check_c_source_compiles(
+    "#include <mpi.h>
+     #include <hdf5.h>
+     int main(void) {
+       hid_t plist = H5Pcreate(H5P_FILE_ACCESS);
+       H5Pset_fapl_mpio(plist, MPI_COMM_WORLD, MPI_INFO_NULL);
+       H5Pclose(plist);
+       return 0;
+     }"
+    IDEFIX_HDF5_HAS_MPI_IO
+  )
+
+  if(IDEFIX_HDF5_HAS_MPI_IO)
+    set(_idefix_hdf5_is_parallel TRUE)
+  endif()
+
+  set(IDEFIX_HDF5_IS_PARALLEL ${_idefix_hdf5_is_parallel} PARENT_SCOPE)
+endfunction()