[python] added OpenMP options for python-package installation (#1975)

* added OpenMP options for python-package installation

* fixed grammar typo

python-package/README.rst

@@ -43,7 +43,17 @@ Build from Sources
 
 For **Linux** and **macOS** users, installation from sources requires installed `CMake`_.
 
-For **macOS** users, you can perform installation either with **Apple Clang** or **gcc**. In case you prefer **Apple Clang**, you should install **OpenMP** (details for installation can be found in `Installation Guide <https://github.com/Microsoft/LightGBM/blob/master/docs/Installation-Guide.rst#apple-clang>`__) first and **CMake** version 3.12 or higher is required. In case you prefer **gcc**, you need to install it (details for installation can be found in `Installation Guide <https://github.com/Microsoft/LightGBM/blob/master/docs/Installation-Guide.rst#gcc>`__) and specify compilers by running ``export CXX=g++-7 CC=gcc-7`` (replace "7" with version of **gcc** installed on your machine) first.
+For **macOS** users, you can perform installation either with **Apple Clang** or **gcc**.
+
+- In case you prefer **Apple Clang**, you should install **OpenMP** (details for installation can be found in `Installation Guide <https://github.com/Microsoft/LightGBM/blob/master/docs/Installation-Guide.rst#apple-clang>`__) first and **CMake** version 3.12 or higher is required.
+
+  In some cases **OpenMP** cannot be found which causes installation failures. So, if you encounter errors during the installation process, try to pass paths to **CMake** via ``pip`` options, like
+
+  .. code:: sh
+
+      pip install lightgbm --install-option="--openmp-include-dir=/usr/local/opt/libomp/include/" --install-option="--openmp-library=/usr/local/opt/libomp/lib/libomp.dylib"
+
+- In case you prefer **gcc**, you need to install it (details for installation can be found in `Installation Guide <https://github.com/Microsoft/LightGBM/blob/master/docs/Installation-Guide.rst#gcc>`__) and specify compilers by running ``export CXX=g++-7 CC=gcc-7`` (replace "7" with version of **gcc** installed on your machine) first.
 
 For **Windows** users, **Visual Studio** (or `VS Build Tools <https://visualstudio.microsoft.com/downloads/>`_) is needed. If you get any errors during installation, you may need to install `CMake`_ (version 3.8 or higher).
 
@@ -129,6 +139,8 @@ Install from GitHub
 
 All remarks from `Build from Sources section <#build-from-sources>`__ are actual in this case.
 
+For **macOS** users who compile with **Apple Clang**, to pass **OpenMP** paths to **CMake** use the following syntax: ``python setup.py install --openmp-include-dir=/usr/local/opt/libomp/include/ --openmp-library=/usr/local/opt/libomp/lib/libomp.dylib``.
+
 For **Windows** users, if you get any errors during installation and there is the warning ``WARNING:LightGBM:Compilation with MSBuild from existing solution file failed.`` in the log, you should install `CMake`_ (version 3.8 or higher).
 
 .. code:: sh

python-package/setup.py

@@ -90,7 +90,8 @@ def silent_call(cmd, raise_error=False, error_msg=''):
 def compile_cpp(use_mingw=False, use_gpu=False, use_mpi=False, nomp=False,
                 use_hdfs=False, boost_root=None, boost_dir=None,
                 boost_include_dir=None, boost_librarydir=None,
-                opencl_include_dir=None, opencl_library=None):
+                opencl_include_dir=None, opencl_library=None,
+                openmp_include_dir=None, openmp_library=None):
 
     if os.path.exists(os.path.join(CURRENT_DIR, "build_cpp")):
         shutil.rmtree(os.path.join(CURRENT_DIR, "build_cpp"))
@@ -118,19 +119,6 @@ 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")
 
@@ -177,6 +165,38 @@ def compile_cpp(use_mingw=False, use_gpu=False, use_mpi=False, nomp=False,
                             error_msg='Please install CMake first')
     else:  # Linux, Darwin (macOS), etc.
         logger.info("Starting to compile with CMake.")
+        # Apple Clang with OpenMP
+        if system() == 'Darwin' and not nomp and not (os.environ.get('CC', '').startswith('gcc')
+                                                      and os.environ.get('CXX', '').startswith('g++')):
+            def get_cmake_opts(openmp_include_dir, openmp_library):
+                if openmp_include_dir and openmp_library:
+                    return ['-DOpenMP_C_FLAGS=-Xpreprocessor -fopenmp -I{0}'.format(openmp_include_dir),
+                            '-DOpenMP_C_LIB_NAMES=omp',
+                            '-DOpenMP_CXX_FLAGS=-Xpreprocessor -fopenmp -I{0}'.format(openmp_include_dir),
+                            '-DOpenMP_CXX_LIB_NAMES=omp',
+                            '-DOpenMP_omp_LIBRARY={0}'.format(openmp_library)]
+                else:
+                    return []
+
+            status = silent_call(cmake_cmd + get_cmake_opts(openmp_include_dir, openmp_library))
+            status += silent_call(["make", "_lightgbm", "-j4"])
+            if status != 0:
+                logger.warning("Compilation failed.")
+                logger.info("Starting to compile with Homebrew OpenMP paths guesses.")
+                clear_path(os.path.join(CURRENT_DIR, "build_cpp"))
+                status = silent_call(cmake_cmd + get_cmake_opts('/usr/local/opt/libomp/include',
+                                                                '/usr/local/opt/libomp/lib/libomp.dylib'))
+                status += silent_call(["make", "_lightgbm", "-j4"])
+            if status != 0:
+                logger.warning("Compilation failed.")
+                logger.info("Starting to compile with MacPorts OpenMP paths guesses.")
+                clear_path(os.path.join(CURRENT_DIR, "build_cpp"))
+                silent_call(cmake_cmd + get_cmake_opts('/opt/local/include/libomp',
+                                                       '/opt/local/lib/libomp/libomp.dylib'),
+                            raise_error=True, error_msg='Please install CMake and all required dependencies first')
+                silent_call(["make", "_lightgbm", "-j4"], raise_error=True,
+                            error_msg='An error has occurred while building lightgbm library file')
+        else:
             silent_call(cmake_cmd, raise_error=True, error_msg='Please install CMake and all required dependencies first')
             silent_call(["make", "_lightgbm", "-j4"], raise_error=True,
                         error_msg='An error has occurred while building lightgbm library file')
@@ -208,7 +228,9 @@ class CustomInstall(install):
         ('boost-include-dir=', None, 'Directory containing Boost headers'),
         ('boost-librarydir=', None, 'Preferred Boost library directory'),
         ('opencl-include-dir=', None, 'OpenCL include directory'),
-        ('opencl-library=', None, 'Path to OpenCL library')
+        ('opencl-library=', None, 'Path to OpenCL library'),
+        ('openmp-include-dir=', None, 'OpenMP include directory'),
+        ('openmp-library=', None, 'Path to OpenMP library')
     ]
 
     def initialize_options(self):
@@ -221,6 +243,8 @@ class CustomInstall(install):
         self.boost_librarydir = None
         self.opencl_include_dir = None
         self.opencl_library = None
+        self.openmp_include_dir = None
+        self.openmp_library = None
         self.mpi = 0
         self.hdfs = 0
         self.precompile = 0
@@ -233,7 +257,8 @@ class CustomInstall(install):
             compile_cpp(use_mingw=self.mingw, use_gpu=self.gpu, use_mpi=self.mpi, nomp=self.nomp,
                         use_hdfs=self.hdfs, boost_root=self.boost_root, boost_dir=self.boost_dir,
                         boost_include_dir=self.boost_include_dir, boost_librarydir=self.boost_librarydir,
-                        opencl_include_dir=self.opencl_include_dir, opencl_library=self.opencl_library)
+                        opencl_include_dir=self.opencl_include_dir, opencl_library=self.opencl_library,
+                        openmp_include_dir=self.openmp_include_dir, openmp_library=self.openmp_library)
         install.run(self)
         if os.path.isfile(LOG_PATH):
             os.remove(LOG_PATH)