Allow manual memory reset in AttentionMechanism (#547)

* Add support for manual memory reset

* Better code style in MyModel class

Remove solved #TODO

Author: kazemnejad

tensorflow_addons/seq2seq/attention_wrapper.py

@@ -179,6 +179,10 @@ def __call__(self, inputs, **kwargs):
           inputs: the inputs tensors.
           **kwargs: dict, other keyeword arguments for the `__call__()`
         """
+        # Allow manual memory reset
+        if kwargs.get('setup_memory', False):
+            self._memory_initialized = False
+
         if self._memory_initialized:
             if len(inputs) not in (2, 3):
                 raise ValueError(
@@ -188,6 +192,7 @@ def __call__(self, inputs, **kwargs):
                 # We append the calculated memory here so that the graph will be
                 # connected.
                 inputs.append(self.values)
+
         return super(_BaseAttentionMechanism, self).__call__(inputs, **kwargs)
 
     def call(self, inputs, mask=None, setup_memory=False, **kwargs):

tensorflow_addons/seq2seq/attention_wrapper_test.py

@@ -209,7 +209,55 @@ def test_masking(self):
         alignment = self.evaluate(alignment)
         self.assertEqual(np.sum(np.triu(alignment, k=1)), 0)
 
-    # TODO(scottzhu): Add tests for model.compile(run_eagerly=True)
+    @parameterized.named_parameters(
+        ("luong", wrapper.LuongAttention),
+        ("luong_monotonic", wrapper.LuongMonotonicAttention),
+        ("bahdanau", wrapper.BahdanauAttention),
+        ("bahdanau_monotonic", wrapper.BahdanauMonotonicAttention),
+    )
+    def test_memory_re_setup(self, attention_cls):
+        class MyModel(tf.keras.models.Model):
+            def __init__(self, vocab, embedding_dim, memory_size, units):
+                super(MyModel, self).__init__()
+                self.emb = tf.keras.layers.Embedding(
+                    vocab, embedding_dim, mask_zero=True)
+                self.encoder = tf.keras.layers.LSTM(
+                    memory_size, return_sequences=True)
+                self.attn_mch = attention_cls(units)
+
+            def call(self, inputs):
+                enc_input, query, state = inputs
+                mask = self.emb.compute_mask(enc_input)
+                enc_input = self.emb(enc_input)
+                enc_output = self.encoder(enc_input, mask=mask)
+                # To ensure manual resetting also works in the graph mode,
+                # we call the attention mechanism twice.
+                self.attn_mch(enc_output, mask=mask, setup_memory=True)
+                self.attn_mch(enc_output, mask=mask, setup_memory=True)
+                score = self.attn_mch([query, state])
+                return score
+
+        vocab = 20
+        embedding_dim = 6
+        num_batches = 5
+
+        model = MyModel(vocab, embedding_dim, self.memory_size, self.units)
+        if tf.executing_eagerly():
+            model.compile("rmsprop", "mse", run_eagerly=True)
+        else:
+            model.compile("rmsprop", "mse")
+
+        x = np.random.randint(
+            vocab, size=(num_batches * self.batch, self.timestep))
+        x_test = np.random.randint(
+            vocab, size=(num_batches * self.batch, self.timestep))
+        y = np.random.randn(num_batches * self.batch, self.timestep)
+
+        query = np.tile(self.query, [num_batches, 1])
+        state = np.tile(self.state, [num_batches, 1])
+
+        model.fit([x, query, state], (y, y), batch_size=self.batch)
+        model.predict_on_batch([x_test, query, state])
 
 
 class ResultSummary(