```
Here we see the directories for all the backend libraries. TH, THC, THNN,  THCUNN, and nccl are git subtrees that are in sync with the libraries in e.g. github.com/torch. THS, THCS, THD, THPP and libshm are libraries specific to PyTorch. All of the libraries contain CMakeLists.txt - indicating they are built with CMake.
The build_all.sh is essentially a script that runs the CMake configure step on all of these libraries, and then make install. Let's run ./build_all.sh and see what we are left with:
```bash
(p3) killeent@devgpu047:lib (master)$ ./build_all.sh --with-cuda --with-nccl --with-distributed
[various CMake output logs]
(p3) killeent@devgpu047:lib (master)$ ls