## Background

I am an HPC administrator for Pitt. A common trend lately is users asking for the newest Tensorflow release the second it is available. However, as many of you probably know, compiling Tensorflow can be a bear. My daily Linux distribution of choice is Arch Linux which is a bleeding edge distribution and Tensorflow 1.4.1 is as easy as sudo pacman -S python-tensorflow-opt-cuda (note, I use the pip package below). However, I have found that building GPU enabled containers is a little tricky because if the underlying NVIDIA libraries don't match it will never run on the GPU. First, we should talk about building HPC containers

## Enter Singularity

Singularity (http://singularity.lbl.gov) is a very powerful tool for reproducible research as well as portable software. It is available on the Arch Linux User Repository (AUR) as singularity-container and can be installed with yaourt -S singularity-container (I have always used yaourt AUR package manager, others exist). If you need to build from source:

git clone https://github.com/singularityware/singularity.git
cd singularity
./autogen.sh
./configure
make
make install
make test

I have never had an issue compiling and installing this code. On Red Hat Enterprise Linux, you will need to sudo make install for everything to work. If you don't have access to install with sudo, add --prefix=<somewhere_you_have_access> --disable-suid to the configure line (via Issue 1258). I am not going to go over the basics of Singularity, check out their documentation for that (or hit me up on Twitter and I'll write about it).

## Setting Up

As I mentioned previously, the tricky part is getting the libraries to match. I installed NVIDIA Drivers/CUDA using an orchestration tool called Warewulf (same developer as Singularity!). On my compute nodes, these libraries are included in the following packages:

1. NVIDIA-Linux-x86_64-384.59.run
2. cuda_8.0.44_linux.run (ships with CuDNN 5)

For TF 1.4.1, you also need CUDNN 6: cucudnn-8.0-linux-x64-v6.0.tgz. Ideally, you would download all of these from the web. In the case of the slightly older Driver/CUDA, I had a harder time finder these online. I keep the source on my Warewulf master for safe keeping. You may need to ask your HPC administrator for these packages.

## Build File

With Singularity, you have some options for building containers and I chose to use a bootstrap file. By convention it is titled Singularity and is essentially a Bash script. First, I will paste the entire file and then break it down section by section.

Bootstrap: docker
From: base/archlinux

%runscript
exec python $* %setup # Mirror list echo 'Server = http://mirror.cs.pitt.edu/archlinux/$repo/os/$arch' >$SINGULARITY_ROOTFS/etc/pacman.d/mirrorlist
echo 'Server = http://mirrors.rit.edu/archlinux/$repo/os/$arch' >> $SINGULARITY_ROOTFS/etc/pacman.d/mirrorlist echo 'Server = http://mirror.es.its.nyu.edu/archlinux/$repo/os/$arch' >>$SINGULARITY_ROOTFS/etc/pacman.d/mirrorlist
echo 'Server = http://mirrors.rutgers.edu/archlinux/$repo/os/$arch' >> $SINGULARITY_ROOTFS/etc/pacman.d/mirrorlist # NVidia VERSION=384.59 sh NVIDIA-Linux-x86_64-$VERSION.run -x
mv NVIDIA-Linux-x86_64-$VERSION$SINGULARITY_ROOTFS/usr/local
cp links.sh $SINGULARITY_ROOTFS/root # CuDNN mkdir$SINGULARITY_ROOTFS/usr/local/cuda
cp -R cudnn/* $SINGULARITY_ROOTFS/usr/local/cuda # CUDA dir=$(pwd)
sh $dir/cuda_8.0.44_linux.run -extract=$dir/cuda
$dir/cuda/cuda-linux64-rel-8.0.44-21122537.run --noexec --keep cp -R$dir/pkg/lib64/* $SINGULARITY_ROOTFS/usr/local/cuda/lib64 # Cleanup rm -rf cuda pkg %environment export LD_LIBRARY_PATH=/usr/local/cuda/lib64:/usr/local/NVIDIA-Linux-x86_64-384.59:$LD_LIBRARY_PATH
export PATH=/usr/local/NVIDIA-Linux-x86_64-384.59:$PATH unset XDG_RUNTIME_DIR %labels AUTHOR barrymoo %post # Process NVIDIA links sh /root/links.sh 384.59 # Install python and pip pacman -Syy --noconfirm python python-pip # Install tensorflow pip install --upgrade tensorflow-gpu ## Metadata This is the only section which doesn't start with a %<section>. In this case I use Bootstrap: docker and From: base/archlinux. I am telling singularity to start with an Arch Linux base image from DockerHub. In the next sections, I will modify that container. ## %runscript This tells the container that when a user runs singularity run tensoflow-gpu.img ... to run python (within the container) with ... as arguments. There is a lot more clever things one can do with this section, but my users basically need to run python <some_script.py> ## %setup I will break this down into a few steps: 1. Generate a list of mirrors for pacman. In the %post section, we need to install things via pacman and will need to refresh mirrors. Note the use of $SINGULARITY_ROOTFS! In this section we are running from outside the container! To refer to the root filesystem of the container we use this environment variable.
2. Install the NVIDIA driver which matches the compute nodes. Copy in the script links.sh, which I borrowed from @clemsonciti on GitHub (thanks!), which we need for inside the container.
3. I already had CuDNN extracted in this directory, simply make the /usr/local/cuda directory and copy CuDNN in.
4. Install CUDA. CUDA comes with 3 components, I only want the CUDA libraries.
5. Finally clean up the stuff we no longer need.

## %environment

This generates a file /environment inside the container which singularity runs when setting up the environment.

## %labels

More metadata. There is probably more useful information I could put in here, but I don't plan to distribute this container (it is specific to my current compute node environment).

## %post

Unlike %setup this section is executed inside the container! Again the steps:

1. Run the links.sh script for our driver version.
2. Install python and pip.
3. Install tensorflow-gpu via pip.

Here, you could install other packages. For example, I know my users will use cython (installed via pip) and gcc (installed via pacman).

## Bootstrap the Container

You will need root to build the container. Therefore, it makes sense to use your own computer: sudo singularity build tensorflow-gpu.img Singularity. After it is done building,

$singularity run tensorflow-gpu.img hello-world.py # a stupid simple hello TF script ... Errors complaining it can't run on GPU due to driver mismatch ... b'Hello TF' 42 From my cluster: $ singularity run tensorflow-gpu.img hello-world.py
...
Creating TensorFlow device (/device:GPU:0) -> (device: 0, name: GeForce GTX 1080, pci bus id: 0000:81:00.0, compute capability: 6.1)
...
b'Hello TF'
42

Fantastic! We are running TF 1.4.1 on a compute node without compiling anything!

## Wrap Up

I think Singularity is fantastic. I spent a lot of time mucking around with compiling TF by hand in our HPC environment. To be fair, I also spent a lot of time mucking around with building Singularity images on GPUs. However, every time a new release of TF comes around I can simply update the container and stop compiling it by hand. As usual, if anyone thinks what I am doing is stupid and you have a better way. Message me on Twitter. Some upcoming blog topics include:

1. Migrating a Grav site (this site) from DigitalOcean to Google Cloud Platform.
2. Using C++17 template fold expressions
3. Writing streaming data applications in the Cloud w/ Python (Dash, Heroku, mLab)
4. Building a proposal system into Slurm