[GitHub] szha commented on a change in pull request #8957: Adding the steps to build MXNet with NCCL

[GitBox <gi...@apache.org>]

szha commented on a change in pull request #8957: Adding the steps to build MXNet with NCCL
URL: https://github.com/apache/incubator-mxnet/pull/8957#discussion_r155841925
 
 

 ##########
 File path: docs/install/build_from_source.md
 ##########
 @@ -317,6 +317,40 @@ Use [CMake](https://cmake.org/) to create a Visual Studio solution in ```./build
 In Visual Studio, open the solution file,```.sln```, and compile it.
 These commands produce a library called ```mxnet.dll``` in the ```./build/Release/``` or ```./build/Debug``` folder.
 
+</div>
+
+<div class="linux ubuntu">
+
+## Build MXNet using NCCL
+- Download and install the latest NCCL library from NVIDIA.
+- Note the directory path in which NCCL libraries and header files are installed.
+- Ensure that the installation directory contains ```lib``` and ```include``` folders.
+- Ensure that the prerequisites for using NCCL such as Cuda libraries are met. 
+- Append the ```config.mk``` file with following, in addition to the CUDA related options.
+- USE_NCCL=1
+- USE_NCCL_PATH=path-to-nccl-installation-folder
+``` bash
+echo "USE_NCCL=1" >> make/config.mk
+echo "USE_NCCP_PATH=path-to-nccl-installation-folder" >> make/config.mk
+cp make/config.mk .
+```
+- Run make command
+``` bash
+make -j"$(nproc)"
+```
+
+## Validation
+- Follow the steps to install MXNet Python binding.
+- Comment the following line in ```test_nccl.py``` file at ```incubator-mxnet/tests/python/gpu/test_nccl.py```
+``` bash
+@unittest.skip("Test requires NCCL library installed and enabled during build")
+```
+- Run test_nccl.py script as follows. The test should complete. It does not produce any output.
+
+## Recommendation for best performance
+It is recommended to set environment variable NCCL_LAUNCH_MODE to PARALLEL when using NCCL version 2.1 or newer.
 
 Review comment:
   Ideally mxnet users should be able to get env var info in that page without searching for nccl page. Consider adding a section for nccl in that page

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