allow non-MPI build option -Dhdf5_parallel=off (default on)

Author: scivision

CMakeLists.txt

@@ -31,32 +31,33 @@ endif()
 include(cmake/options.cmake)
 include(cmake/compilers.cmake)
 
-if(ourFindMPI)
-  list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/Modules/MPI)
+if(hdf5_parallel)
+  find_package(MPI COMPONENTS C Fortran REQUIRED)
+
+  include(cmake/check_mpi.cmake)
+  check_mpi_version()
+
+  find_package(HDF5 COMPONENTS Fortran parallel REQUIRED)
+  if(HDF5_VERSION VERSION_LESS 1.10.2)
+    message(WARNING "HDF5 >= 1.10.2 is needed for HDF5-MPI")
+  endif()
+else()
+  find_package(HDF5 COMPONENTS Fortran REQUIRED)
 endif()
 
-find_package(MPI COMPONENTS C Fortran REQUIRED)
-
-
-# --- external libraries:  HDF5
-
-include(cmake/check_mpi.cmake)
-check_mpi_version()
-
-find_package(HDF5 COMPONENTS Fortran HL parallel REQUIRED)
-if(HDF5_VERSION VERSION_LESS 1.10.2)
-  message(WARNING "HDF5 >= 1.10.2 is needed for HDF5-MPI")
-endif()
-
-# --- HDF5-MPI object oriented API
+# --- h5fortran object oriented API
 
 add_library(h5fortran)
-target_compile_definitions(h5fortran PRIVATE -Dh5fortran_HAVE_PARALLEL)
+target_compile_definitions(h5fortran PRIVATE
+$<$<BOOL:${hdf5_parallel}>:h5fortran_HAVE_PARALLEL>
+)
 target_include_directories(h5fortran PUBLIC
 $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>
 $<INSTALL_INTERFACE:include>
 )
-target_link_libraries(h5fortran PUBLIC HDF5::HDF5 MPI::MPI_Fortran)
+target_link_libraries(h5fortran PUBLIC HDF5::HDF5
+$<$<BOOL:${hdf5_parallel}>:MPI::MPI_Fortran>
+)
 set_target_properties(h5fortran PROPERTIES
 Fortran_MODULE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/include
 LABELS core

README.md

@@ -7,11 +7,9 @@
 [![intel-oneapi](https://github.com/geospace-code/h5fortran-mpi/actions/workflows/intel-oneapi.yml/badge.svg)](https://github.com/geospace-code/h5fortran-mpi/actions/workflows/intel-oneapi.yml)
 
 Easy to use object-oriented Fortran [parallel HDF5-MPI](https://portal.hdfgroup.org/display/HDF5/Parallel+HDF5) interface.
-This interface requires MPI, although it is capable of non-MPI file I/O.
-The original object-oriented Fortran HDF5 interface **without MPI** is [h5fortran](https://github.com/geospace-code/h5fortran).
-The [h5fortran-mpi API](./API.md)
-is by design nearly identical to the non-MPI serial h5fortran API.
-A very similar NetCDF4 interface is [nc4fortran](https://github.com/geospace-code/nc4fortran).
+The [h5fortran-mpi API](./API.md) can be used with or with MPI.
+A very similar NetCDF4 interface is
+[nc4fortran](https://github.com/geospace-code/nc4fortran).
 
 Many computer systems default to the serial HDF5 API, which lacks the HDF5 parallel MPI layer.
 The scripts/CMakeLists.txt can build the HDF5-MPI stack if needed.
@@ -24,7 +22,7 @@ Some OS have an installable parallel HDF5 package:
 * MacOS Homebrew: `brew install hdf5-mpi`
 * MacOS MacPorts: `port install hdf5 +fortran +mpich`
 
-While HDF5 1.10.2 is the oldest working HDF5 version, and the CI includes HDF5 1.10.4, in general for bugfixes and performance HDF5 ≥ 1.10.5 is [recommended](https://portal.hdfgroup.org/display/knowledge/OpenMPI+Build+Issues).
+While HDF5 1.10.2 is the oldest working HDF5 version, in general for bugfixes and performance HDF5 ≥ 1.10.5 is [recommended](https://portal.hdfgroup.org/display/knowledge/OpenMPI+Build+Issues).
 For highest performance with parallel compressed writes consider HDF5 ≥ 1.12.2.
 
 ## Compressed parallel HDF5
@@ -62,12 +60,19 @@ cmake -B build -DHDF5_ROOT=~/lib_par
 cmake --build build
 ```
 
+To build without MPI (serial HDF5 file operations only):
+
+```sh
+cmake -B build -Dhdf5_parallel=off
+```
+
 ---
 
 Fortran Package Manager (FPM) users build like:
 
 ```sh
 fpm build --flag -Dh5fortran_HAVE_PARALLEL
+# omitting this flag builds the serial API only
 
 fpm test
 ```

cmake/hdf5.cmake

@@ -8,7 +8,7 @@ if(hdf5_parallel)
   find_package(MPI REQUIRED COMPONENTS C)
 endif()
 
-# pass MPI hints to HDF5
+# pass MPI hints to HDF5, which needs it as a CMake variable--HDF5 project doesn't detect ENV{MPI_ROOT}
 if(NOT MPI_ROOT AND DEFINED ENV{MPI_ROOT})
   set(MPI_ROOT $ENV{MPI_ROOT})
 endif()

cmake/options.cmake

@@ -1,22 +1,15 @@
-option(ENABLE_BENCHMARKS "write / read benchmarks")
+message(STATUS "${PROJECT_NAME} ${PROJECT_VERSION}  CMake ${CMAKE_VERSION}")
 
+option(ENABLE_BENCHMARKS "write / read benchmarks")
 option(ENABLE_COVERAGE "Code coverage tests")
-
-option(ourFindMPI "Use our FindMPI")
-
-message(STATUS "${PROJECT_NAME} ${PROJECT_VERSION}  CMake ${CMAKE_VERSION}")
+option(hdf5_parallel "use HDF5-MPI layer" true)
 
 set(CMAKE_TLS_VERIFY true)
 
 
-if(BUILD_SHARED_LIBS)
-  if(WIN32 AND CMAKE_VERSION VERSION_LESS 3.21 AND ${PROJECT_NAME}_BUILD_TESTING)
-    message(STATUS "Windows with shared libs needs CMake >= 3.21 to run tests")
-  endif()
-  if(MSVC)
-    message(WARNING "Intel oneAPI has trouble with shared libs in general on Windows, try
-      cmake -DBUILD_SHARED_LIBS=off")
-  endif()
+if(BUILD_SHARED_LIBS AND MSVC)
+  message(WARNING "Intel oneAPI has trouble with shared libs in general on Windows, try
+    cmake -DBUILD_SHARED_LIBS=off")
 endif()
 
 cmake_path(SET CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR}/Modules)

test/CMakeLists.txt

@@ -1,20 +1,6 @@
 set_directory_properties(PROPERTIES LABELS unit)
 
-# --- unit tests
-
-add_executable(test_runner runner.f90
-${PROJECT_SOURCE_DIR}/benchmark/cpu.cpp
-${PROJECT_SOURCE_DIR}/benchmark/partition.f90
-${PROJECT_SOURCE_DIR}/benchmark/cli.f90
-)
-# not linked as libraries in case benchmarks aren't built
-if(CMAKE_Fortran_COMPILER_ID MATCHES "^Intel")
-  set_target_properties(test_runner PROPERTIES LINKER_LANGUAGE Fortran)
-else()
-  set_target_properties(test_runner PROPERTIES LINKER_LANGUAGE CXX)
-endif()
-
-# --- h5fortran unit tests
+# --- helper functions
 
 function(nompi_test names)
 
@@ -58,20 +44,42 @@ add_test(NAME ${name} COMMAND ${cmd})
 endforeach()
 
 set_tests_properties(${names} PROPERTIES
-RESOUCE_LOCK cpu_mpi
+RESOURCE_LOCK cpu_mpi
 LABELS mpi
 )
 
 endfunction(mpi_test)
 
+# --- test files
+
 cmake_path(SET string_file ${CMAKE_CURRENT_BINARY_DIR}/test_string_py.h5)
 
-# --- write test data
+# --- non-MPI tests
 
 set(nompi_tests array)
 
 nompi_test(${nompi_tests})
 
+
+# --- runner
+
+if(hdf5_parallel)
+
+add_executable(test_runner runner.f90
+${PROJECT_SOURCE_DIR}/benchmark/cpu.cpp
+${PROJECT_SOURCE_DIR}/benchmark/partition.f90
+${PROJECT_SOURCE_DIR}/benchmark/cli.f90
+)
+# not linked as libraries in case benchmarks aren't built
+if(CMAKE_Fortran_COMPILER_ID MATCHES "^Intel")
+  set_target_properties(test_runner PROPERTIES LINKER_LANGUAGE Fortran)
+else()
+  set_target_properties(test_runner PROPERTIES LINKER_LANGUAGE CXX)
+endif()
+
+
+# --- MPI tests
+
 set(mpi_tests array_mpi attributes cast destructor exist fill groups layout shape
 string string_read write
 )
@@ -136,6 +144,8 @@ FIXTURES_SETUP h5str
 DISABLED $<NOT:$<BOOL:${h5py_ok}>>
 )
 
+endif(hdf5_parallel)
+
 # --- test properties
 
 get_property(test_names DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY TESTS)