PyTorch is a Python deep learning library that's currently gaining a lot of traction, because it's a lot easier to debug and prototype (compared to TensorFlow / Theano).
To install PyTorch on the Duckietbot you have to compile it from source, because there is no pro-compiled binary for ARMv7 / ARMhf available. This guid will walk you through the required steps.
First you need to install some additional packages. You might already have installed. If you do, that's not a problem.
sudo apt-get install libopenblas-dev cython libatlas-dev m4 libblas-dev
In your current shell add two flags for the compiler
export NO_CUDA=1 # this will disable CUDA components of PyTorch, because the little RaspberriPi doesn't have a GPU that supports CUDA
export NO_DISTRIBUTED=1 # no idea what this does, but it fixed a compilation bug for me
Then cd into a directory of your choice, like cd ~/Downloads or something like that and clone the PyTorch library.
git clone --recursive https://github.com/pytorch/pytorch
There was recently a bug in the ARM-relevant code that should now be fixed in the main Github branch, but just to make sure you have the most recent code:...
Change into the directory that you just cloned, and further into the following direcotries:
cd pytorch/torch/lib/ATen/
...and check that the file Scalar.h has the following code on line 16:
Scalar() : Scalar(int64_t(0)) {}
If the line instead reads the following, please manually change the code to the above line:
Scalar() : Scalar(0L) {}
When I was compiling the library I ran out of SWAP space (which is 500MB by default). I was successful in compiling it with 2GB of SWAP space. Here is how you can increase the SWAP (only for compilation - later we will switch back to 500MB).
Create the swap file of 2GB
sudo dd if=/dev/zero of=/swap1 bs=1M count=2048
Make this empty file into a swap-compatible file
sudo mkswap /swap1
Then disable the old swap space and enable the new one
sudo nano /etc/fstab
This above command will open a text editor on your /etc/fstab file. The file should have this as the last line: /swap0 swap swap. In this line, please change the /swap0 to /swap1. Then save the file with CTRL+o and ENTER. Close the editor with CTRL+x.
Now your system knows about the new swap space, and it will change it upon reboot, but if you want to use it right now, without reboot, you can manually turn off & empty the old swap space and enable the new one:
sudo swapoff /swap0
sudo swapon /swap1
cd into the main directory, that you clones PyTorch into, in my case cd ~/Downloads/pytorch and start the compilation process:
python setup.py build
This shouldn't create any errors but it took me about an hour. If it does throw some exceptions, please let me know.
When it's done, you can install the pytorch package system-wide with
sudo python setup.py install
For some reason on my machine this caused recompilation of a few packages. So this might again take some time (but should be significantly less).
If all of the above went through without any issues, congratulations. :) You should now have a working PyTorch installation. You can try it out like this.
First you need to change out of the installation directory (this is important - otherwise you get a really weird error):
cd ~
Then run Python:
python
And on the Python interpreter try this:
import torch
a = torch.FloatTensor((2,2))
a.add_(3)
print (a)
...this should print something like this:
3 3
3 3
[torch.FloatTensor of size 2x2]
Now if you like having 2GB of SWAP space (additional RAM basically, but a lot slower than your built-in RAM), then you are done. The downside is that you might run out of space later on. If you want to revert back to your old 500MB swap file then do the following:
Open the /etc/fstab file in the editor:
sudo nano /etc/fstab
TODO
please change the /swap0 to /swap1. Then save the file with CTRL+o and ENTER. Close the editor with CTRL+x.