Important: This notebook will only work with fastai-0.7.x. Do not try to run any fastai-1.x code from this path in the repository because it will load fastai-0.7.x
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%reload_ext autoreload
%autoreload 2
%matplotlib inline
from fastai.learner import *
from fastai.column_data import *
Data available from http://files.grouplens.org/datasets/movielens/ml-latest-small.zip
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path='data/ml-latest-small/'
We're working with the movielens data, which contains one rating per row, like this:
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ratings = pd.read_csv(path+'ratings.csv')
ratings.head()
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Just for display purposes, let's read in the movie names too.
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movies = pd.read_csv(path+'movies.csv')
movies.head()
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We create a crosstab of the most popular movies and most movie-addicted users which we'll copy into Excel for creating a simple example. This isn't necessary for any of the modeling below however.
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g=ratings.groupby('userId')['rating'].count()
topUsers=g.sort_values(ascending=False)[:15]
g=ratings.groupby('movieId')['rating'].count()
topMovies=g.sort_values(ascending=False)[:15]
top_r = ratings.join(topUsers, rsuffix='_r', how='inner', on='userId')
top_r = top_r.join(topMovies, rsuffix='_r', how='inner', on='movieId')
pd.crosstab(top_r.userId, top_r.movieId, top_r.rating, aggfunc=np.sum)
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val_idxs = get_cv_idxs(len(ratings))
wd=2e-4
n_factors = 50
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cf = CollabFilterDataset.from_csv(path, 'ratings.csv', 'userId', 'movieId', 'rating')
learn = cf.get_learner(n_factors, val_idxs, 64, opt_fn=optim.Adam)
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learn.fit(1e-2, 2, wds=wd, cycle_len=1, cycle_mult=2)
Let's compare to some benchmarks. Here's some benchmarks on the same dataset for the popular Librec system for collaborative filtering. They show best results based on RMSE of 0.91. We'll need to take the square root of our loss, since we use plain MSE.
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math.sqrt(0.776)
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Looking good - we've found a solution better than any of those benchmarks! Let's take a look at how the predictions compare to actuals for this model.
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preds = learn.predict()
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y=learn.data.val_y
sns.jointplot(preds, y, kind='hex', stat_func=None);
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movie_names = movies.set_index('movieId')['title'].to_dict()
g=ratings.groupby('movieId')['rating'].count()
topMovies=g.sort_values(ascending=False).index.values[:3000]
topMovieIdx = np.array([cf.item2idx[o] for o in topMovies])
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m=learn.model; m.cuda()
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First, we'll look at the movie bias term. Here, our input is the movie id (a single id), and the output is the movie bias (a single float).
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movie_bias = to_np(m.ib(V(topMovieIdx)))
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movie_bias
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movie_ratings = [(b[0], movie_names[i]) for i,b in zip(topMovies,movie_bias)]
Now we can look at the top and bottom rated movies. These ratings are corrected for different levels of reviewer sentiment, as well as different types of movies that different reviewers watch.
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sorted(movie_ratings, key=lambda o: o[0])[:15]
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sorted(movie_ratings, key=itemgetter(0))[:15]
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sorted(movie_ratings, key=lambda o: o[0], reverse=True)[:15]
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We can now do the same thing for the embeddings.
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movie_emb = to_np(m.i(V(topMovieIdx)))
movie_emb.shape
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Because it's hard to interpret 50 embeddings, we use PCA to simplify them down to just 3 vectors.
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from sklearn.decomposition import PCA
pca = PCA(n_components=3)
movie_pca = pca.fit(movie_emb.T).components_
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movie_pca.shape
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fac0 = movie_pca[0]
movie_comp = [(f, movie_names[i]) for f,i in zip(fac0, topMovies)]
Here's the 1st component. It seems to be 'easy watching' vs 'serious'.
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sorted(movie_comp, key=itemgetter(0), reverse=True)[:10]
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sorted(movie_comp, key=itemgetter(0))[:10]
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fac1 = movie_pca[1]
movie_comp = [(f, movie_names[i]) for f,i in zip(fac1, topMovies)]
Here's the 2nd component. It seems to be 'CGI' vs 'dialog driven'.
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sorted(movie_comp, key=itemgetter(0), reverse=True)[:10]
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sorted(movie_comp, key=itemgetter(0))[:10]
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We can draw a picture to see how various movies appear on the map of these components. This picture shows the first two components.
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idxs = np.random.choice(len(topMovies), 50, replace=False)
X = fac0[idxs]
Y = fac1[idxs]
plt.figure(figsize=(15,15))
plt.scatter(X, Y)
for i, x, y in zip(topMovies[idxs], X, Y):
plt.text(x,y,movie_names[i], color=np.random.rand(3)*0.7, fontsize=11)
plt.show()
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a = T([[1.,2],[3,4]])
b = T([[2.,2],[10,10]])
a,b
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a*b
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(a*b).sum(1)
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class DotProduct(nn.Module):
def forward(self, u, m): return (u*m).sum(1)
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model=DotProduct()
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model(a,b)
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u_uniq = ratings.userId.unique()
user2idx = {o:i for i,o in enumerate(u_uniq)}
ratings.userId = ratings.userId.apply(lambda x: user2idx[x])
m_uniq = ratings.movieId.unique()
movie2idx = {o:i for i,o in enumerate(m_uniq)}
ratings.movieId = ratings.movieId.apply(lambda x: movie2idx[x])
n_users=int(ratings.userId.nunique())
n_movies=int(ratings.movieId.nunique())
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class EmbeddingDot(nn.Module):
def __init__(self, n_users, n_movies):
super().__init__()
self.u = nn.Embedding(n_users, n_factors)
self.m = nn.Embedding(n_movies, n_factors)
self.u.weight.data.uniform_(0,0.05)
self.m.weight.data.uniform_(0,0.05)
def forward(self, cats, conts):
users,movies = cats[:,0],cats[:,1]
u,m = self.u(users),self.m(movies)
return (u*m).sum(1).view(-1, 1)
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x = ratings.drop(['rating', 'timestamp'],axis=1)
y = ratings['rating'].astype(np.float32)
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data = ColumnarModelData.from_data_frame(path, val_idxs, x, y, ['userId', 'movieId'], 64)
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wd=1e-5
model = EmbeddingDot(n_users, n_movies).cuda()
opt = optim.SGD(model.parameters(), 1e-1, weight_decay=wd, momentum=0.9)
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fit(model, data, 3, opt, F.mse_loss)
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set_lrs(opt, 0.01)
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fit(model, data, 3, opt, F.mse_loss)
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min_rating,max_rating = ratings.rating.min(),ratings.rating.max()
min_rating,max_rating
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def get_emb(ni,nf):
e = nn.Embedding(ni, nf)
e.weight.data.uniform_(-0.01,0.01)
return e
class EmbeddingDotBias(nn.Module):
def __init__(self, n_users, n_movies):
super().__init__()
(self.u, self.m, self.ub, self.mb) = [get_emb(*o) for o in [
(n_users, n_factors), (n_movies, n_factors), (n_users,1), (n_movies,1)
]]
def forward(self, cats, conts):
users,movies = cats[:,0],cats[:,1]
um = (self.u(users)* self.m(movies)).sum(1)
res = um + self.ub(users).squeeze() + self.mb(movies).squeeze()
res = F.sigmoid(res) * (max_rating-min_rating) + min_rating
return res.view(-1, 1)
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wd=2e-4
model = EmbeddingDotBias(cf.n_users, cf.n_items).cuda()
opt = optim.SGD(model.parameters(), 1e-1, weight_decay=wd, momentum=0.9)
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fit(model, data, 3, opt, F.mse_loss)
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set_lrs(opt, 1e-2)
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fit(model, data, 3, opt, F.mse_loss)
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class EmbeddingNet(nn.Module):
def __init__(self, n_users, n_movies, nh=10, p1=0.05, p2=0.5):
super().__init__()
(self.u, self.m) = [get_emb(*o) for o in [
(n_users, n_factors), (n_movies, n_factors)]]
self.lin1 = nn.Linear(n_factors*2, nh)
self.lin2 = nn.Linear(nh, 1)
self.drop1 = nn.Dropout(p1)
self.drop2 = nn.Dropout(p2)
def forward(self, cats, conts):
users,movies = cats[:,0],cats[:,1]
x = self.drop1(torch.cat([self.u(users),self.m(movies)], dim=1))
x = self.drop2(F.relu(self.lin1(x)))
return F.sigmoid(self.lin2(x)) * (max_rating-min_rating+1) + min_rating-0.5
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wd=1e-5
model = EmbeddingNet(n_users, n_movies).cuda()
opt = optim.Adam(model.parameters(), 1e-3, weight_decay=wd)
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fit(model, data, 3, opt, F.mse_loss)
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set_lrs(opt, 1e-3)
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fit(model, data, 3, opt, F.mse_loss)
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