apex安装走过的路

行路时千难万险，回头看也只是云淡风轻

一、pip 安装apex

pip安装apex很简单，但是使用会提示：

ModuleNotFoundError: No module named 'fused_layer_norm_cuda'

二、从源码安装apex

git clone https://github.com/NVIDIA/apex
cd apex
# Build with core extensions (cpp and cuda)
APEX_CPP_EXT=1 APEX_CUDA_EXT=1 pip install -v --no-build-isolation .

# To build with additional extensions, specify them with environment variables
APEX_CPP_EXT=1 APEX_CUDA_EXT=1 APEX_FAST_MULTIHEAD_ATTN=1 APEX_FUSED_CONV_BIAS_RELU=1 pip install -v --no-build-isolation .

# To build all contrib extensions at once
APEX_CPP_EXT=1 APEX_CUDA_EXT=1 APEX_ALL_CONTRIB_EXT=1 pip install -v --no-build-isolation .

这是官网安装的步骤，不过正常的情况下，肯定会有意外发生的，对的吧。所以来看我为走过的路。

三、安装中遇到的问题

3.1 GNU version

提示错误如下：

unsupported GNU version! gcc versions later than 12 are not supported! The nvcc flag '-allow-unsupported-compiler' can be used to override this version check; however, using an unsupported host compiler may cause compilation failure or incorrect run time execution. Use at your own risk.

主要原因：gcc版本高了，你可以选择降级，不过我选择忽略。我是ubuntu，所以：

export NVCC_APPEND_FLAGS=-allow-unsupported-compiler

设置过之后。

我使用的是conda 环境：

各个环境如下：

torch                     2.7.1
torchvision               0.22.1
CUDA Version: 12.9

于是出现了如下问题：

3.2 nvcc' failed with exit code 127

sh: 1: /home/pyUser/anaconda3/envs/pytorch/bin/../targets/x86_64-linux/nvvm/bin/cicc: not found
error: command '/home/pyUser/anaconda3/envs/pytorch/bin/nvcc' failed with exit code 127

到这一步就快成功了，只需要指定CONA_HOME就行了

CUDA_HOME=/usr/local/cuda-12.9 APEX_CPP_EXT=1 APEX_CUDA_EXT=1 pip install -v --no-build-isolation .

但是：一定要注意CONA_HOME和CUDA Version版本要一致，这就是我来时路

道阻且长,行则将至