update the subrepository

README.md

@@ -54,7 +54,8 @@ source /usr/local/bin/fastpt -C
 ```
 2. 编译whl包并安装
 ```shell
-cd pytorch_sparce || torch-sparce
+cd torch-sparce
+git submodule update --init --recursive  # 更新子仓
 python setup.py bdist_wheel
 pip install dist/*.whl
 ```