Build with libomp 11.1 and package it in the macOS wheel (#5679)

Fail build if newer libomp found
Install libomp 11.1.0 from old brew bottle for catalina (10.15)

.github/workflows/macos.yml

@@ -20,7 +20,7 @@ concurrency:
 
 env:
   # https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources
-  NPROC: 3
+  NPROC: 4
   DEVELOPER_BUILD: ${{ github.event.inputs.developer_build || 'ON' }}
 
 jobs:
@@ -59,7 +59,13 @@ jobs:
       - name: Install dependencies
         run: |
           brew install ccache pkg-config
-          brew link --force libomp  # needed for cmake to find OpenMP
+          # Install libomp 11.1.0 from old brew bottle for catalina (10.15).
+          # Directly installing the Ruby formula will install for the current OS
+          # https://github.com/microsoft/LightGBM/issues/4229
+          brew unlink libomp
+          curl -L -H "Authorization: Bearer QQ==" -o libomp-11.1.0.catalina.bottle.tar.gz \
+          https://ghcr.io/v2/homebrew/core/libomp/blobs/sha256:45a5aa653bd45bd5ff5858580b1a4670c4b5a51ea29d68d45a53f72f56010e05
+          brew install -f libomp-11.1.0.catalina.bottle.tar.gz
           ccache -M 2G  # See .github/workflows/readme.md for ccache strategy.
       - name: Config and build
         run: |
@@ -170,7 +176,12 @@ jobs:
           cmake --version
           source util/ci_utils.sh
           install_python_dependencies
+          # Install libomp 11.1.0. See comment above.
           brew install ccache
+          brew unlink libomp
+          curl -L -H "Authorization: Bearer QQ==" -o libomp-11.1.0.catalina.bottle.tar.gz \
+          https://ghcr.io/v2/homebrew/core/libomp/blobs/sha256:45a5aa653bd45bd5ff5858580b1a4670c4b5a51ea29d68d45a53f72f56010e05
+          brew install -f libomp-11.1.0.catalina.bottle.tar.gz
           ccache -M 2G  # See .github/workflows/readme.md for ccache strategy.
 
       - name: Config and build wheel

cpp/pybind/CMakeLists.txt

@@ -65,9 +65,30 @@ if (BUILD_GUI AND CMAKE_SYSTEM_NAME STREQUAL "Linux")
     list(APPEND PYTHON_EXTRA_LIBRARIES ${CPP_LIBRARY}.1 ${CPPABI_LIBRARY}
         ${MESA_CPU_GL_LIBRARY})
 endif()
+if (WITH_OPENMP AND APPLE AND NOT BUILD_SHARED_LIBS)
+# Package libomp v11.1.0, if it is not installed. Later version cause crash on
+# x86_64 if PyTorch is already imported. Case of shared libopen3d.dylib is not
+# handled.
+# https://github.com/microsoft/LightGBM/issues/4229
+    list(APPEND PYTHON_EXTRA_LIBRARIES ${OpenMP_libomp_LIBRARY})
+    execute_process(COMMAND brew list --versions libomp
+        COMMAND cut "-d\ " -f2
+        OUTPUT_VARIABLE libomp_ver OUTPUT_STRIP_TRAILING_WHITESPACE)
+    if(libomp_ver VERSION_GREATER_EQUAL 12.0.0)
+        message(SEND_ERROR "libomp ${libomp_ver} found, which can lead to interoperability problems with other Python libraries using libomp.  Please use libomp v11.1 to build Open3D.")
+    endif()
+    file(GENERATE OUTPUT update_pybind_libomp.sh
+        CONTENT [=[libomp_library=$(dyld_info -dependents "$<TARGET_FILE:pybind>" |
+grep libomp | tr -d '[:space:]')
+install_name_tool -change $libomp_library @loader_path/../libomp.dylib \
+"$<TARGET_FILE:pybind>"]=])
+    add_custom_command(TARGET pybind POST_BUILD
+        COMMAND bash update_pybind_libomp.sh
+        COMMENT "Updating pybind to use packaged libomp")
+endif()
 
 # Use `make python-package` to create the python package in the build directory
-# The python package will be created at PYTHON_PACKAGE_DIR. It contains:
+# The python package will be created at PYTHON_PACKAGE_DST_DIR. It contains:
 # 1) Pure-python code and misc files, copied from python/package
 # 2) The compiled python-C++ module, i.e. open3d.so (or the equivalents)
 # 3) Configured files and supporting files
@@ -84,8 +105,8 @@ set(GENERATED_OUTPUTS "")
 
 # add additional optional compiled modules
 if (BUILD_TENSORFLOW_OPS)
-    list( APPEND COMPILED_MODULE_PATH_LIST $<TARGET_FILE:open3d_tf_ops> )
-    add_custom_command( OUTPUT "${CMAKE_BINARY_DIR}/lib/ml/tf/python/ops/ops.py"
+    list(APPEND COMPILED_MODULE_PATH_LIST $<TARGET_FILE:open3d_tf_ops> )
+    add_custom_command(OUTPUT "${CMAKE_BINARY_DIR}/lib/ml/tf/python/ops/ops.py"
             COMMAND ${Python3_EXECUTABLE} generate_tf_ops_wrapper.py --input "${PYTHON_PACKAGE_SRC_DIR}/open3d/ml/tf/python/ops/ops.py.in" --output "${CMAKE_BINARY_DIR}/lib/ml/tf/python/ops/ops.py" --lib $<TARGET_FILE:open3d_tf_ops>
                         DEPENDS open3d_tf_ops
                         WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}

docs/getting_started.in.rst

@@ -43,16 +43,6 @@ Pip (PyPI)
 
         ``pip install -U pip>=20.3``
 
-.. note::
-   In MacOS, please install ``libomp`` (OpenMP) on your system before installing
-   Open3D.
-
-        ``brew install libomp``
-
-    We do not package OpenMP runtime with Open3D since a system OpenMP runtime
-    ensures more reliable interoperation with other Python packages (e.g.
-    PyTorch) that also use OpenMP.
-
 .. note::
     In general, we recommend using a
     `virtual environment <https://docs.python-guide.org/dev/virtualenvs/>`_