Add wikilinks NN method for generating embeddings

src/wikirec/model.py

@@ -25,6 +25,15 @@
 
 from wikirec import utils
 
+import os
+import json
+import random
+from itertools import chain
+from collections import Counter, OrderedDict
+from keras.models import load_model
+from keras.layers import Input, Embedding, Dot, Reshape, Dense
+from keras.models import Model
+
 
 def gen_embeddings(
     method="lda",
@@ -64,6 +73,10 @@ def gen_embeddings(
                     - Word importance increases proportionally to the number of times a word appears in the document while being offset by the number of documents in the corpus that contain the word
 
                     - These importances are then vectorized and used to relate documents
+
+                Wikilinks
+
+                    - Generate an embedding using a neural network trained on the connections between articles and the internal wikilinks
 
         corpus : list of lists (default=None)
             The text corpus over which analysis should be done
@@ -141,6 +154,17 @@ def gen_embeddings(
         embeddings = tfidfvectoriser.transform(corpus)
 
         return embeddings
+
+    elif method == "wikilinks":
+        if os.path.isfile("./wikilinks_embedding_model.h5"):
+            model = load_model("./wikilinks_embedding_model.h5")
+            layer = model.get_layer('book_embedding')
+            weights = layer.get_weights()[0]
+            embeddings = weights / np.linalg.norm(weights, axis = 1).reshape((-1, 1))
+            return embeddings
+        else:
+            embeddings = _wikilinks_nn()
+            return embeddings
 
 
 def gen_sim_matrix(
@@ -327,3 +351,134 @@ def recommend(
     recommendations = [r for r in recommendations if r[0] not in inputs][:n]
 
     return recommendations
+
+def _wikilinks_nn(path_to_json = None, embedding_size = 50):
+    """
+    Generates embeddings of wikilinks and articles by training a neural network. Currently only trained on books.  
+
+    Parameters
+    ----------
+        path_to_json : str (default=None)
+            The path to the parsed json file. 
+
+        embedding_size : int (default = 50)
+            The length of the embedding vectors between the articles and the links.
+
+    Returns
+    -------
+        book_weights : np.array
+            The normalized embedding vectors for each of the articles. 
+
+            Shape of book_weights is (len(books), embedding_size)
+
+    """
+    if os.path.isfile(path_to_json):
+        with open(path_to_json, "r") as fin:
+            books = [json.loads(l) for l in fin]
+    else:
+        raise Exception("Need to parse json for books.")
+
+    # Find set of wikilinks for each book and convert to a flattened list
+    unique_wikilinks = list(chain(*[list(set(book[2])) for book in books]))
+    wikilinks = [link.lower() for link in unique_wikilinks]
+    to_remove = ['hardcover', 'paperback', 'hardback', 'e-book', 'wikipedia:wikiproject books', 'wikipedia:wikiproject novels']
+    wikilinks = [item for item in wikilinks if item not in to_remove]
+
+    # Limit to wikilinks that occur more than 4 times
+    wikilinks_counts = Counter(wikilinks)
+    wikilinks_counts = sorted(wikilinks_counts.items(), key = lambda x: x[1], reverse = True)
+    wikilinks_counts = OrderedDict(wikilinks_counts)
+    links = [t[0] for t in wikilinks_counts.items() if t[1] >= 4]
+
+    # map books to their indices, and map links to indices as well 
+    book_index = {book[0]: idx for idx, book in enumerate(books)}
+    link_index = {link: idx for idx, link in enumerate(links)} 
+
+    #Create data from pairs of (book, wikilink) for training the neural network embedding
+    pairs = []
+    for book in books:
+        title = book[0]
+        book_links = book[2]
+        # Iterate through wikilinks in book article
+        for link in book_links:
+            # Add index of book and index of link to pairs
+            if link.lower() in links:
+                pairs.append((book_index[title], link_index[link.lower()]))
+    pairs_set = set(pairs)
+
+    # Neural network architecture
+    # Both inputs are 1-dimensional
+    book_input = Input(name = 'book', shape = [1])
+    link_input = Input(name = 'link', shape = [1])
+
+    # Embedding the book (shape will be (None, 1, 50))
+    book_embedding = Embedding(name = 'book_embedding',
+                               input_dim = len(book_index),
+                               output_dim = embedding_size)(book_input)
+
+    # Embedding the link (shape will be (None, 1, 50))
+    link_embedding = Embedding(name = 'link_embedding',
+                               input_dim = len(link_index),
+                               output_dim = embedding_size)(link_input)
+
+    # Merge the layers with a dot product along the second axis 
+    # (shape will be (None, 1, 1))
+    merged = Dot(name = 'dot_product', normalize = True, 
+                 axes = 2)([book_embedding, link_embedding])
+
+    # Reshape to be a single number (shape will be (None, 1))
+    merged = Reshape(target_shape = [1])(merged)
+
+    model = Model(inputs = [book, link], outputs = merged)
+    model.compile(optimizer = 'Adam', loss = 'mse')
+
+    # Function that creates a generator for training data 
+    def _generate_batch(pairs, n_positive = 50, negative_ratio = 1.0):
+        """Generate batches of samples for training. 
+           Random select positive samples
+           from pairs and randomly select negatives."""
+
+        # Create empty array to hold batch
+        batch_size = n_positive * (1 + negative_ratio)
+        batch = np.zeros((batch_size, 3))
+
+        # Continue to yield samples
+        while True:
+            # Randomly choose positive examples
+            for idx, (book_id, link_id) in enumerate(random.sample(pairs, n_positive)):
+                batch[idx, :] = (book_id, link_id, 1)
+            idx += 1
+
+            # Add negative examples until reach batch size
+            while idx < batch_size:
+
+                # Random selection
+                random_book = random.randrange(len(book_index))
+                random_link = random.randrange(len(link_index))
+
+                # Check to make sure this is not a positive example
+                if (random_book, random_link) not in pairs_set:
+
+                    # Add to batch and increment index
+                    batch[idx, :] = (random_book, random_link, 0)
+                    idx += 1
+
+            # Make sure to shuffle order
+            np.random.shuffle(batch)
+            yield {'book': batch[:, 0], 'link': batch[:, 1]}, batch[:, 2]
+
+    n_positive = 1024
+    gen = _generate_batch(pairs, n_positive, negative_ratio = 2)
+    h = model.fit_generator(gen, epochs = 15, steps_per_epoch = len(pairs) // n_positive)
+
+    # Save the model and extract embeddings 
+    model.save('./wikilinks_embedding_model.h5')
+
+    # Extract embeddings
+    book_layer = model.get_layer('book_embedding')
+    book_weights = book_layer.get_weights()[0]
+
+    # Normalize the weights to have norm of 1 
+    book_weights = book_weights / np.linalg.norm(book_weights, axis = 1).reshape((-1, 1))
+
+    return book_weights