Title:  Building Pytorch on an Old Laptop
Brief:  Journey of building Pytorch 2.2.0 on 10+ old amd64 laptop.
Date:   1707822832
Tags:   Compilation, Bash
CSS:    /style.css

This started when I was following my first tutorial on Pytorch to generate toponyms (will probably write about it too later).
Just as I got enough courage to run it for first time I was faced with heartbreaking words, - `Illegal instruction`. Here's the following story:

First I downloaded Pytorch release:
```
git clone --depth 1 https://github.com/pytorch/pytorch --single-branch --branch v2.2.0 pytorch

```

Then struggled for a bit with initialization of submodules, it looks like there are broken links or something???
Anyway, the command is:
```
git submodule update --init --recursive

```
But I had to `rm -fr ./third_party/<> && git rm -fr --cached ./third_party/<>` and then `git submodule add ...` replace a few libs.

Later by trial and error I came up with this script which excludes every part that demands AVX
as well as anything not necessary, as compilation time of it all is ridiculous:

```bash
#!/bin/sh

set +e

# Could comment or override it if you have different compiler you want to use.
export CMAKE_C_COMPILER=clang
export CMAKE_CXX_COMPILER=clang++
export USE_CCACHE=ON

export USE_CUDA=0
export USE_DISTRIBUTED=0
export USE_GLOO=0
export BUILD_TEST=0
export BUILD_CAFFE2=0
export USE_CUDNN=0
export USE_ASAN=0
export USE_MKLDNN=0
export USE_KINETO=0
export DEBUG=0
export USE_XNNPACK=0
export USE_FBGEMM=0
export USE_NNPACK=0
export USE_QNNPACK=0

# You can comment this, but for me throttling was making it slower than just using a single core.
export MAX_JOBS=1

export USE_AVX=OFF
export USE_NNPACK=OFF
export USE_MKLDNN=OFF
export USE_FBGEMM=OFF
export C_HAS_AVX_2=OFF
export C_HAS_AVX2_2=OFF
export CXX_HAS_AVX_2=OFF
export CXX_HAS_AVX2_2=OFF
export CAFFE2_COMPILER_SUPPORTS_AVX512_EXTENSIONS=OFF
export USE_NATIVE_ARCH=ON
export USE_VULKAN=OFF

export USE_SYSTEM_ZSTD=ON

# You can install those from your package manager, but only if you're on up-to-date repos. (so, not stable Debian)
# export USE_SYSTEM_PYBIND11=ON
# export USE_SYSTEM_CPUINFO=ON
# export USE_SYSTEM_SLEEF=ON

python3 setup.py develop

```

It installs itself with dependencies on this very git folder, so you better place it somewhere permanent (I ended up `mv` and `ln` it, just to not forget and delete it from ~/tmp/)

Not sure how to clean the temporary stuff properly after installation, it wastes quite a bit of space (1.7 GiB for me).

In the end I just used this, which shredded about 400 MiBs of space:
```
rm -fr ./third_party
cd ./build && find . -name \*.o -type f -delete

```

That's about it. It's slow but you can play with it for small tasks.