Merge pull request #2026 from kkiesling/find_mpi

use find_package(mpi) instead of relying on compilers

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.3 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.10 FATAL_ERROR)
 project(openmc C CXX)
 
 # Set version numbers
@@ -30,6 +30,7 @@ option(OPENMC_ENABLE_PROFILE  "Compile with profiling flags"
 option(OPENMC_ENABLE_COVERAGE "Compile with coverage analysis flags"                 OFF)
 option(OPENMC_USE_DAGMC       "Enable support for DAGMC (CAD) geometry"              OFF)
 option(OPENMC_USE_LIBMESH     "Enable support for libMesh unstructured mesh tallies" OFF)
+option(OPENMC_USE_MPI         "Enable MPI"                                           OFF)
 
 #===============================================================================
 # Set a default build configuration if not explicitly specified
@@ -44,10 +45,8 @@ endif()
 # MPI for distributed-memory parallelism
 #===============================================================================
 
-set(MPI_ENABLED FALSE)
-if(${CMAKE_CXX_COMPILER} MATCHES "(mpi[^/]*|CC)$")
-  message(STATUS "Detected MPI wrapper: ${CMAKE_CXX_COMPILER}")
-  set(MPI_ENABLED TRUE)
+if(OPENMC_USE_MPI)
+  find_package(MPI REQUIRED)
 endif()
 
 #===============================================================================
@@ -108,7 +107,7 @@ endif()
 
 find_package(HDF5 REQUIRED COMPONENTS C HL)
 if(HDF5_IS_PARALLEL)
-  if(NOT MPI_ENABLED)
+  if(NOT OPENMC_USE_MPI)
     message(FATAL_ERROR "Parallel HDF5 was detected, but the detected compiler,\
      ${CMAKE_CXX_COMPILER}, does not support MPI. An MPI-capable compiler must \
      be used with parallel HDF5.")
@@ -144,6 +143,7 @@ set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 if(OPENMC_ENABLE_PROFILE)
   list(APPEND cxxflags -g -fno-omit-frame-pointer)
 endif()
+
 if(OPENMC_ENABLE_COVERAGE)
   list(APPEND cxxflags --coverage)
   list(APPEND ldflags --coverage)
@@ -399,7 +399,7 @@ target_include_directories(libopenmc PRIVATE ${CMAKE_BINARY_DIR}/include)
 if (HDF5_IS_PARALLEL)
   target_compile_definitions(libopenmc PRIVATE -DPHDF5)
 endif()
-if (MPI_ENABLED)
+if (OPENMC_USE_MPI)
   target_compile_definitions(libopenmc PUBLIC -DOPENMC_MPI)
 endif()
 
@@ -441,6 +441,10 @@ if (PNG_FOUND)
   target_link_libraries(libopenmc PNG::PNG)
 endif()
 
+if (OPENMC_USE_MPI)
+  target_link_libraries(libopenmc MPI::MPI_CXX)
+endif()
+
 #===============================================================================
 # openmc executable
 #===============================================================================

Dockerfile

@@ -59,8 +59,7 @@ ENV LIBMESH_INSTALL_DIR=$HOME/LIBMESH
 ENV NJOY_REPO='https://github.com/njoy/NJOY2016'
 
 # Setup environment variables for Docker image
-ENV CC=/usr/bin/mpicc CXX=/usr/bin/mpicxx \
-    LD_LIBRARY_PATH=${DAGMC_INSTALL_DIR}/lib:$LD_LIBRARY_PATH \
+ENV LD_LIBRARY_PATH=${DAGMC_INSTALL_DIR}/lib:$LD_LIBRARY_PATH \
     OPENMC_CROSS_SECTIONS=/root/nndc_hdf5/cross_sections.xml \
     OPENMC_ENDF_DATA=/root/endf-b-vii.1 \
     DEBIAN_FRONTEND=noninteractive
@@ -179,6 +178,7 @@ RUN mkdir -p ${HOME}/OpenMC && cd ${HOME}/OpenMC \
     && mkdir build && cd build ; \
     if [ ${build_dagmc} = "on" ] && [ ${build_libmesh} = "on" ]; then \
         cmake ../openmc \
+            -DOPENMC_USE_MPI=on \
             -DHDF5_PREFER_PARALLEL=on \
             -DOPENMC_USE_DAGMC=on \
             -DOPENMC_USE_LIBMESH=on \
@@ -186,18 +186,21 @@ RUN mkdir -p ${HOME}/OpenMC && cd ${HOME}/OpenMC \
     fi ; \
     if [ ${build_dagmc} = "on" ] && [ ${build_libmesh} = "off" ]; then \
         cmake ../openmc \
+            -DOPENMC_USE_MPI=on \
             -DHDF5_PREFER_PARALLEL=on \
             -DOPENMC_USE_DAGMC=ON \
             -DCMAKE_PREFIX_PATH=${DAGMC_INSTALL_DIR} ; \
     fi ; \
     if [ ${build_dagmc} = "off" ] && [ ${build_libmesh} = "on" ]; then \
         cmake ../openmc \
+            -DOPENMC_USE_MPI=on \
             -DHDF5_PREFER_PARALLEL=on \
             -DOPENMC_USE_LIBMESH=on \
             -DCMAKE_PREFIX_PATH=${LIBMESH_INSTALL_DIR} ; \
     fi ; \
     if [ ${build_dagmc} = "off" ] && [ ${build_libmesh} = "off" ]; then \
         cmake ../openmc \
+            -DOPENMC_USE_MPI=on \
             -DHDF5_PREFER_PARALLEL=on ; \
     fi ; \
     make 2>/dev/null -j${compile_cores} install \

cmake/OpenMCConfig.cmake.in

@@ -21,3 +21,7 @@ find_package(PNG)
 if(NOT TARGET OpenMC::libopenmc)
   include("${OpenMC_CMAKE_DIR}/OpenMCTargets.cmake")
 endif()
+
+if(@OPENMC_USE_MPI@)
+  find_package(MPI REQUIRED)
+endif()

docs/source/usersguide/install.rst

@@ -203,7 +203,7 @@ Prerequisites
       respectively. To link against a parallel HDF5 library, make sure to set
       the HDF5_PREFER_PARALLEL CMake option, e.g.::
 
-          CXX=mpicxx.mpich cmake -DHDF5_PREFER_PARALLEL=on ..
+          cmake -DHDF5_PREFER_PARALLEL=on -DOPENMC_USE_MPI=on ..
 
       Note that the exact package names may vary depending on your particular
       distribution and version.
@@ -263,7 +263,7 @@ Prerequisites
       installation should be specified as part of the ``CMAKE_PREFIX_PATH``
       variable.::
 
-          CXX=mpicxx cmake -DOPENMC_USE_LIBMESH=on -DCMAKE_PREFIX_PATH=/path/to/libmesh/installation
+          cmake -DOPENMC_USE_LIBMESH=on -DOPENMC_USE_MPI=on -DCMAKE_PREFIX_PATH=/path/to/libmesh/installation
 
       Note that libMesh is most commonly compiled with MPI support. If that
       is the case, then OpenMC should be compiled with MPI support as well.
@@ -352,6 +352,10 @@ OPENMC_ENABLE_COVERAGE
   Compile and link code instrumented for coverage analysis. This is typically
   used in conjunction with gcov_. (Default: off)
 
+OPENMC_USE_MPI
+  Turns on compiling with MPI (default: off). For further information on MPI options,
+  please see the `FindMPI.cmake documentation <https://cmake.org/cmake/help/latest/module/FindMPI.html>`_.
+
 To set any of these options (e.g., turning on profiling), the following form
 should be used:
 
@@ -384,24 +388,6 @@ Example of configuring for Debug mode:
 
     cmake -DCMAKE_BUILD_TYPE=Debug /path/to/openmc
 
-Compiling with MPI
-++++++++++++++++++
-
-To compile with MPI, set the :envvar:`CXX` environment variable to the path to
-the MPI C++ wrapper. For example, in a bash shell:
-
-.. code-block:: sh
-
-    export CXX=mpicxx
-    cmake /path/to/openmc
-
-Note that in many shells, environment variables can be set for a single command,
-i.e.
-
-.. code-block:: sh
-
-    CXX=mpicxx cmake /path/to/openmc
-
 Selecting HDF5 Installation
 +++++++++++++++++++++++++++
 

tests/regression_tests/cpp_driver/test.py

@@ -33,12 +33,14 @@ def cpp_driver(request):
     os.chdir(str(local_builddir))
 
     if config['mpi']:
-        os.environ['CXX'] = 'mpicxx'
+        mpi_arg = "On"
+    else:
+        mpi_arg = "Off"
 
     try:
         print("Building driver")
         # Run cmake/make to build the shared libary
-        subprocess.run(['cmake', os.path.pardir], check=True)
+        subprocess.run(['cmake', os.path.pardir, f'-DOPENMC_USE_MPI={mpi_arg}'], check=True)
         subprocess.run(['make'], check=True)
         os.chdir(os.path.pardir)
 

tests/regression_tests/external_moab/test.py

@@ -49,12 +49,14 @@ def cpp_driver(request):
     os.chdir(str(local_builddir))
 
     if config['mpi']:
-        os.environ['CXX'] = 'mpicxx'
+        mpi_arg = "On"
+    else:
+        mpi_arg = "Off"
 
     try:
         print("Building driver")
         # Run cmake/make to build the shared libary
-        subprocess.run(['cmake', os.path.pardir], check=True)
+        subprocess.run(['cmake', os.path.pardir, f'-DOPENMC_USE_MPI={mpi_arg}'], check=True)
         subprocess.run(['make'], check=True)
         os.chdir(os.path.pardir)
 

tools/ci/gha-install.py

@@ -34,7 +34,7 @@ def install(omp=False, mpi=False, phdf5=False, dagmc=False, libmesh=False):
 
     # Use MPI wrappers when building in parallel
     if mpi:
-        os.environ['CXX'] = 'mpicxx'
+        cmake_cmd.append('-DOPENMC_USE_MPI=on')
 
     # Tell CMake to prefer parallel HDF5 if specified
     if phdf5: