teacher forcing with combining

layers/tacotron.py

@@ -236,7 +236,7 @@ class Decoder(nn.Module):
         # RNN_state -> |Linear| -> mel_spec
         self.proj_to_mel = nn.Linear(256, memory_dim * r)
 
-    def forward(self, inputs, memory=None, memory_lengths=None):
+    def forward(self, inputs, memory=None, input_lengths=None):
         r"""
         Decoder forward step.
 
@@ -247,7 +247,7 @@ class Decoder(nn.Module):
             inputs: Encoder outputs.
             memory: Decoder memory (autoregression. If None (at eval-time),
               decoder outputs are used as decoder inputs.
-            memory_lengths: Encoder output (memory) lengths. If not None, used for
+            input_lengths: Encoder output (memory) lengths. If not None, used for
               attention masking.
 
         Shapes:
@@ -258,8 +258,8 @@ class Decoder(nn.Module):
 
         # TODO: take this segment into Attention module.
         processed_inputs = self.input_layer(inputs)
-        if memory_lengths is not None:
+        if input_lengths is not None:
-            mask = get_mask_from_lengths(processed_inputs, memory_lengths)
+            mask = get_mask_from_lengths(processed_inputs, input_lengths)
         else:
             mask = None
 
@@ -300,7 +300,17 @@ class Decoder(nn.Module):
         memory_input = initial_memory
         while True:
             if t > 0:
-                memory_input = outputs[-1] if greedy else memory[t - 1]
+                # using harmonized teacher-forcing.
+                # from https://arxiv.org/abs/1707.06588
+                if greedy:
+                    memory_input = outputs[-1]
+                else:
+                    # combine prev. model output and prev. real target
+                    memory_input = torch.div(outputs[-1] + memory[t-1], 2.0)
+                    # add a random noise
+                    memory_input += torch.autograd.Variable(
+                        torch.randn(memory_input.size())).type_as(memory_input)
+
             # Prenet
             processed_memory = self.prenet(memory_input)
 

models/tacotron.py

@@ -34,12 +34,13 @@ class Tacotron(nn.Module):
         encoder_outputs = self.encoder(inputs)
 
         if self.use_memory_mask:
-            memory_lengths = input_lengths
+            input_lengths = input_lengths
         else:
-            memory_lengths = None
+            input_lengths = None
+
         # (B, T', mel_dim*r)
         mel_outputs, alignments = self.decoder(
-            encoder_outputs, mel_specs, memory_lengths=memory_lengths)
+            encoder_outputs, mel_specs, input_lengths=input_lengths)
 
         # Post net processing below