Add OpenMP support (#1761)

CMakeLists.txt

@@ -62,6 +62,7 @@ option(BUILD_RNNT "Enable RNN transducer" ON)
 option(BUILD_TORCHAUDIO_PYTHON_EXTENSION "Build Python extension" OFF)
 option(USE_CUDA "Enable CUDA support" OFF)
 option(USE_ROCM "Enable ROCM support" OFF)
+option(USE_OPENMP "Enable OpenMP support" OFF)
 
 
 # check that USE_CUDA and USE_ROCM are not set at the same time
@@ -122,6 +123,10 @@ if(MSVC)
   endif()
 endif()
 
+if(USE_OPENMP)
+  find_package(OpenMP REQUIRED)
+endif()
+
 # TORCH_CXX_FLAGS contains the same -D_GLIBCXX_USE_CXX11_ABI value as PyTorch
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall ${TORCH_CXX_FLAGS}")
 

tools/setup_helpers/extension.py

@@ -39,6 +39,8 @@ _BUILD_KALDI = False if platform.system() == 'Windows' else _get_build("BUILD_KA
 _BUILD_RNNT = _get_build("BUILD_RNNT", True)
 _USE_ROCM = _get_build("USE_ROCM", torch.cuda.is_available() and torch.version.hip is not None)
 _USE_CUDA = _get_build("USE_CUDA", torch.cuda.is_available() and torch.version.hip is None)
+_USE_OPENMP = _get_build("USE_OPENMP", True) and \
+    'ATen parallel backend: OpenMP' in torch.__config__.parallel_info()
 _TORCH_CUDA_ARCH_LIST = os.environ.get('TORCH_CUDA_ARCH_LIST', None)
 
 
@@ -90,6 +92,7 @@ class CMakeBuild(build_ext):
             "-DBUILD_TORCHAUDIO_PYTHON_EXTENSION:BOOL=ON",
             f"-DUSE_ROCM:BOOL={'ON' if _USE_ROCM else 'OFF'}",
             f"-DUSE_CUDA:BOOL={'ON' if _USE_CUDA else 'OFF'}",
+            f"-DUSE_OPENMP:BOOL={'ON' if _USE_OPENMP else 'OFF'}",
         ]
         build_args = [
             '--target', 'install'

torchaudio/csrc/CMakeLists.txt

@@ -94,6 +94,10 @@ if (MSVC)
     set_target_properties(libtorchaudio PROPERTIES SUFFIX ".pyd")
 endif(MSVC)
 
+if(OpenMP_CXX_FOUND)
+  target_link_libraries(libtorchaudio OpenMP::OpenMP_CXX)
+endif()
+
 install(
   TARGETS libtorchaudio
   LIBRARY DESTINATION lib