Summary:
---
How does the current code subsume all detections in the deleted `nccl.py`?
- The dependency of `USE_NCCL` on the OS and `USE_CUDA` is handled as dependency options in `CMakeLists.txt`.
- The main NCCL detection happens in [FindNCCL.cmake](8377d4b32c/cmake/Modules/FindNCCL.cmake), which is called by [nccl.cmake](8377d4b32c/cmake/External/nccl.cmake). When `USE_SYSTEM_NCCL` is false, the previous Python code defer the detection to `find_package(NCCL)`. The change in `nccl.cmake` retains this.
- `USE_STATIC_NCCL` in the previous Python code simply changes the name of the detected library. This is done in `IF (USE_STATIC_NCCL)`.
- Now we only need to look at how the lines below line 20 in `nccl.cmake` are subsumed. These lines list paths to header and library directories that NCCL headers and libraries may reside in and try to search these directories for the key header and library files in turn. These are done by `find_path` for headers and `find_library` for the library files in `FindNCCL.cmake`.
* The call of [find_path](https://cmake.org/cmake/help/v3.8/command/find_path.html) (Search for `NO_DEFAULT_PATH` in the link) by default searches for headers in `<prefix>/include` for each `<prefix>` in `CMAKE_PREFIX_PATH` and `CMAKE_SYSTEM_PREFIX_PATH`. Like the Python code, this commit sets `CMAKE_PREFIX_PATH` to search for `<prefix>` in `NCCL_ROOT_DIR` and home to CUDA. `CMAKE_SYSTEM_PREFIX_PATH` includes the standard directories such as `/usr/local` and `/usr`. `NCCL_INCLUDE_DIR` is also specifically handled.
* Similarly, the call of [find_library](https://cmake.org/cmake/help/v3.8/command/find_library.html) (Search for `NO_DEFAULT_PATH` in the link) by default searches for libraries in directories including `<prefix>/lib` for each `<prefix>` in `CMAKE_PREFIX_PATH` and `CMAKE_SYSTEM_PREFIX_PATH`. But it also handles the edge cases intended to be solved in the Python code more properly:
- It only searches for `<prefix>/lib64` (and `<prefix>/lib32`) if it is appropriate on the system.
- It only searches for `<prefix>/lib/<arch>` for the right `<arch>`, unlike the Python code searches for `lib/<arch>` in a generic way (e.g., the Python code searches for `/usr/lib/x86_64-linux-gnu` but in reality systems have `/usr/lib/x86_64-some-customized-name-linux-gnu`, see https://unix.stackexchange.com/a/226180/38242 ).
---
Regarding for relevant issues:
- https://github.com/pytorch/pytorch/issues/12063 and https://github.com/pytorch/pytorch/issues/2877: These are properly handled, as explained in the updated comment.
- https://github.com/pytorch/pytorch/issues/2941 does not changes NCCL detection specifically for Windows (it changed CUDA detection).
- b7e258f81ef61d19b884194cdbcd6c7089636d46 A versioned library detection is added, but the order is reversed: The unversioned library becomes preferred. This is because normally unversioned libraries are linked to versioned libraries and preferred by users, and local installation by users are often unversioned. Like the document of [find_library](https://cmake.org/cmake/help/v3.8/command/find_library.html) suggests:
> When using this to specify names with and without a version suffix, we recommend specifying the unversioned name first so that locally-built packages can be found before those provided by distributions.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22930
Differential Revision: D16440275
Pulled By: ezyang
fbshipit-source-id: 11fe80743d4fe89b1ed6f96d5d996496e8ec01aa
* [c10d] Process Group NCCL implementation
* Addressed comments
* Added one missing return and clang format again
* Use cmake/Modules for everything and fix gloo build
* Fixed compiler warnings
* Deleted duplicated FindNCCL
* Have PyTorch depend on minimal libcaffe2.so instead of libATen.so
* Build ATen tests as a part of Caffe2 build
* Hopefully cufft and nvcc fPIC fixes
* Make ATen install components optional
* Add tests back for ATen and fix TH build
* Fixes for test_install.sh script
* Fixes for cpp_build/build_all.sh
* Fixes for aten/tools/run_tests.sh
* Switch ATen cmake calls to USE_CUDA instead of NO_CUDA
* Attempt at fix for aten/tools/run_tests.sh
* Fix typo in last commit
* Fix valgrind call after pushd
* Be forgiving about USE_CUDA disable like PyTorch
* More fixes on the install side
* Link all libcaffe2 during test run
* Make cuDNN optional for ATen right now
* Potential fix for non-CUDA builds
* Use NCCL_ROOT_DIR environment variable
* Pass -fPIC through nvcc to base compiler/linker
* Remove THCUNN.h requirement for libtorch gen
* Add Mac test for -Wmaybe-uninitialized
* Potential Windows and Mac fixes
* Move MSVC target props to shared function
* Disable cpp_build/libtorch tests on Mac
* Disable sleef for Windows builds
* Move protos under BUILD_CAFFE2
* Remove space from linker flags passed with -Wl
* Remove ATen from Caffe2 dep libs since directly included
* Potential Windows fixes
* Preserve options while sleef builds
* Force BUILD_SHARED_LIBS flag for Caffe2 builds
* Set DYLD_LIBRARY_PATH and LD_LIBRARY_PATH for Mac testing
* Pass TORCH_CUDA_ARCH_LIST directly in cuda.cmake
* Fixes for the last two changes
* Potential fix for Mac build failure
* Switch Caffe2 to build_caffe2 dir to not conflict
* Cleanup FindMKL.cmake
* Another attempt at Mac cpp_build fix
* Clear cpp-build directory for Mac builds
* Disable test in Mac build/test to match cmake
Summary:
Latest version of Gloo takes care of MPI_Init/MPI_Finalize for us, so
this commit removes handling that from caffe2/contrib/gloo. It also
imports CMake NCCL module changes from Gloo to stay consistent and
allow setting NCCL_INCLUDE_DIR and NCCL_LIB_DIR separately.
Closes https://github.com/caffe2/caffe2/pull/1295
Reviewed By: dzhulgakov
Differential Revision: D5979364
Pulled By: pietern
fbshipit-source-id: 794b00b0a445317c30a13cc8f0f4dc38e590cc77
Summary:
Use HINTS instead of PATHS for find_library so that you can specify
-DNCCL_ROOT_DIR and it will use this NCCL installation regardless of
what else is installed on your system. Also add a path hint to include
the default base path for NCCL 2 libraries.
Closes https://github.com/caffe2/caffe2/pull/1152
Reviewed By: Yangqing
Differential Revision: D5740053
Pulled By: pietern
fbshipit-source-id: 43f0908a63e8a9b90320dece0bbb558827433b48
