Place the Netflix prize data in the data/ folder. It can be downloaded
from Kaggle:
https://www.kaggle.com/netflix-inc/netflix-prize-data

Change the training settings by editing train_naive.py. Training loss
evolution is saved to the results/ folder.

Example run:
    python preprocess.py
    python split_data.py 100k
    python compute_means.py 100k
    python train_naive_2.py cuda 100k
    python validate_2.py 100k

Valid customer limits:
    1k
    10k
    25k
    100k
    all