如何在docker环境下通过源代码编译mmcv

在docker容器内对mmcv的源代码通过cuda进行编译时报错
OSError: CUDA_HOME environment variable is not set. Please set it to your CUDA install root.

关于这一点，很多人没有说明清楚，这里对这一需求做一个说明：

环境说明

通过docker-compose up 运行，并且使用配置

deploy:
      mode: replicated
      resources:
        reservations:
          devices:
            - driver: nvidia
              capabilities: [ gpu ]
              count: all 
          memory: 8g 

挂载了显卡

在容器中能正常使用显卡

nvidia-smi

+-----------------------------------------------------------------------------+
| NVIDIA-SMI 510.47.03    Driver Version: 510.47.03    CUDA Version: 11.6     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|===============================+======================+======================|
|   0  NVIDIA GeForce ...  Off  | 00000000:17:00.0 Off |                  N/A |
|  0%   43C    P8    11W / 275W |      6MiB / 11264MiB |      0%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+
|   1  NVIDIA GeForce ...  Off  | 00000000:65:00.0 Off |                  N/A |
|  0%   43C    P8    13W / 275W |    101MiB / 11264MiB |      0%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                                  |
|  GPU   GI   CI        PID   Type   Process name                  GPU Memory |
|        ID   ID                                                   Usage      |
|=============================================================================|
|    0   N/A  N/A      1003      G   /usr/lib/xorg/Xorg                  4MiB |
|    1   N/A  N/A      1003      G   /usr/lib/xorg/Xorg                 39MiB |
|    1   N/A  N/A      1516      G   /usr/bin/gnome-shell               58MiB |
+-----------------------------------------------------------------------------+

报错信息

下载mmcv后 ，在mmcv文件路径运行

cd mmcv
MMCV_WITH_OPS=1 pip install -e .

以安装mmcv-full，出现错误

root@3be4a3494460:/home/MMCV_Frame/mmcv# MMCV_WITH_OPS=1 pip install -e .
Looking in indexes: https://pypi.tuna.tsinghua.edu.cn/simple
Obtaining file:///home/MMCV_Frame/mmcv
    ERROR: Command errored out with exit status 1:
     command: /opt/conda/bin/python -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/home/MMCV_Frame/mmcv/setup.py'"'"'; __file__='"'"'/home/MMCV_Frame/mmcv/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-jl7t6bh1
         cwd: /home/MMCV_Frame/mmcv/
    Complete output (13 lines):
    Traceback (most recent call last):
      File "", line 1, in <module>
      File "/home/MMCV_Frame/mmcv/setup.py", line 422, in <module>
        ext_modules=get_extensions(),
      File "/home/MMCV_Frame/mmcv/setup.py", line 331, in get_extensions
        extra_compile_args=extra_compile_args)
      File "/opt/conda/lib/python3.7/site-packages/torch/utils/cpp_extension.py", line 932, in CUDAExtension
        library_dirs += library_paths(cuda=True)
      File "/opt/conda/lib/python3.7/site-packages/torch/utils/cpp_extension.py", line 1040, in library_paths
        if (not os.path.exists(_join_cuda_home(lib_dir)) and
      File "/opt/conda/lib/python3.7/site-packages/torch/utils/cpp_extension.py", line 2058, in _join_cuda_home
        raise EnvironmentError('CUDA_HOME environment variable is not set. '
    OSError: CUDA_HOME environment variable is not set. Please set it to your CUDA install root.
    ----------------------------------------
WARNING: Discarding file:///home/MMCV_Frame/mmcv. Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

解决办法

参考了别人的很多没用的办法就不说了，这里写一个自己突然想到的一个有效解决办法：

运行时挂载 /usr/local/cuda:/usr/local/cuda:ro

这里的路径根据每个人的机子不同会有差异，通过$(which nvcc) 的返回信息/usr/local/cuda/bin/nvcc 可以找到cuda的路径，把cuda的路径挂载到容器中就行了。

再次运行

export CUDA_HOME='/usr/local/cuda'
cd mmcv
MMCV_WITH_OPS=1 pip install -e .

等了10来分钟，编译完毕。

另外，编译过程是真的慢，而且找了半天的多线程编译都没有效果，pip的多线程编译居然没有人关心…

如果不对mmcv或者mmdet的框架进行修改的话，还是建议到官网使用pip直接安装有预编译的版本，会快很多。