sudo apt-get install nvidia-cuda-toolkit

THCudaCheck FAIL file=/tmp/luarocks_cutorch-scm-1-1028/cutorch/lib/THC/THCGeneral.c line=66 error=30 : unknown error
package cunn not found!
package cutorch not found!
If cutorch and cunn are installed, your CUDA toolkit may be improperly configured.
Check your CUDA toolkit installation, rebuild cutorch and cunn, and try again.
Falling back on CPU mode
~/torch/install/share/lua/5.1/torch/File.lua:343: unknown Torch class <torch.CudaTensor>

luarocks install cutorch
luarocks install cunn