Fix build on macOS Mojave (#1923)

* Fix build on macOS Mojave

Fixed #1898

- https://iscinumpy.gitlab.io/post/omp-on-high-sierra/
- https://cliutils.gitlab.io/modern-cmake/chapters/packages/OpenMP.html
- https://github.com/Homebrew/homebrew-core/pull/20589

* update setup.py

* update docs

* fix setup.py

* update docs

* update docs

* update setup.py

* update docs

CMakeLists.txt

@@ -211,8 +211,8 @@ endif(USE_MPI)
 
 if(USE_OPENMP)
     if(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
-        TARGET_LINK_LIBRARIES(lightgbm ${OpenMP_libomp_LIBRARY})
-        TARGET_LINK_LIBRARIES(_lightgbm ${OpenMP_libomp_LIBRARY})
+        TARGET_LINK_LIBRARIES(lightgbm OpenMP::OpenMP_CXX)
+        TARGET_LINK_LIBRARIES(_lightgbm OpenMP::OpenMP_CXX)
     endif()
 endif(USE_OPENMP)
 

docs/Installation-Guide.rst

@@ -146,7 +146,19 @@ Only **Apple Clang** version 8.1 or higher is supported.
 
      git clone --recursive https://github.com/Microsoft/LightGBM ; cd LightGBM
      mkdir build ; cd build
+
+     # For Mojave (10.14)
+     cmake \
+       -DOpenMP_C_FLAGS="-Xpreprocessor -fopenmp -I$(brew --prefix libomp)/include" \
+       -DOpenMP_C_LIB_NAMES="omp" \
+       -DOpenMP_CXX_FLAGS="-Xpreprocessor -fopenmp -I$(brew --prefix libomp)/include" \
+       -DOpenMP_CXX_LIB_NAMES="omp" \
+       -DOpenMP_omp_LIBRARY=$(brew --prefix libomp)/lib/libomp.dylib \
+       ..
+
+     # For High Sierra or earlier (<= 10.13)
      cmake ..
+
      make -j4
 
 gcc
@@ -436,7 +448,20 @@ Only **Apple Clang** version 8.1 or higher is supported.
 
      git clone --recursive https://github.com/Microsoft/LightGBM ; cd LightGBM
      mkdir build ; cd build
+
+     # For Mojave (10.14)
+     cmake \
+       -DUSE_MPI=ON \
+       -DOpenMP_C_FLAGS="-Xpreprocessor -fopenmp -I$(brew --prefix libomp)/include" \
+       -DOpenMP_C_LIB_NAMES="omp" \
+       -DOpenMP_CXX_FLAGS="-Xpreprocessor -fopenmp -I$(brew --prefix libomp)/include" \
+       -DOpenMP_CXX_LIB_NAMES="omp" \
+       -DOpenMP_omp_LIBRARY=$(brew --prefix libomp)/lib/libomp.dylib \
+       ..
+
+     # For High Sierra or earlier (<= 10.13)
      cmake -DUSE_MPI=ON ..
+
      make -j4
 
 gcc

python-package/setup.py

@@ -118,8 +118,22 @@ def compile_cpp(use_mingw=False, use_gpu=False, use_mpi=False, nomp=False,
         cmake_cmd.append("-DUSE_MPI=ON")
     if nomp:
         cmake_cmd.append("-DUSE_OPENMP=OFF")
+    if system() == 'Darwin' and not nomp:
+        cc = os.environ.get('CC')
+        cxx = os.environ.get('CXX')
+        if not (cc and cc.startswith('gcc') and cxx and cxx.startswith('g++')):
+            # Apple Clang
+            # https://github.com/Homebrew/homebrew-core/pull/20589
+            cmake_cmd.extend([
+                '-DOpenMP_C_FLAGS=-Xpreprocessor -fopenmp -I/usr/local/opt/libomp/include',
+                '-DOpenMP_C_LIB_NAMES=omp',
+                '-DOpenMP_CXX_FLAGS=-Xpreprocessor -fopenmp -I/usr/local/opt/libomp/include',
+                '-DOpenMP_CXX_LIB_NAMES=omp',
+                '-DOpenMP_omp_LIBRARY=/usr/local/opt/libomp/lib/libomp.dylib'
+            ])
     if use_hdfs:
         cmake_cmd.append("-DUSE_HDFS=ON")
+
     if system() in ('Windows', 'Microsoft'):
         if use_mingw:
             if use_mpi: