update adaptive softmax head

pytorch_pretrained_bert/modeling_transfo_xl_utilities.py

@@ -89,15 +89,23 @@ class ProjectedAdaptiveLogSoftmax(nn.Module):
 
         return logit
 
-    def forward(self, hidden, target, keep_order=False):
+    def forward(self, hidden, target=None, keep_order=False):
         '''
+            Params:
                 hidden :: [len*bsz x d_proj]
                 target :: [len*bsz]
+            Return:
+                if target is None:
+                    out :: [len*bsz] Negative log likelihood
+                else:
+                    out :: [len*bsz x n_tokens] log probabilities of tokens over the vocabulary
             We could replace this implementation by the native PyTorch one
-            if their was an option to set bias on all clusters in the native one.
-            line https://github.com/pytorch/pytorch/blob/dbe6a7a9ff1a364a8706bf5df58a1ca96d2fd9da/torch/nn/modules/adaptive.py#L138
+            if their's had an option to set bias on all clusters in the native one.
+            here: https://github.com/pytorch/pytorch/blob/dbe6a7a9ff1a364a8706bf5df58a1ca96d2fd9da/torch/nn/modules/adaptive.py#L138
         '''
 
+        if target is not None:
+            target = target.view(-1)
             if hidden.size(0) != target.size(0):
                 raise RuntimeError('Input and target should have the same size '
                                 'in the batch dimension.')
@@ -105,8 +113,11 @@ class ProjectedAdaptiveLogSoftmax(nn.Module):
         if self.n_clusters == 0:
             logit = self._compute_logit(hidden, self.out_layers[0].weight,
                                         self.out_layers[0].bias, self.out_projs[0])
-            nll = -F.log_softmax(logit, dim=-1) \
+            if target is not None:
+                output = -F.log_softmax(logit, dim=-1) \
                         .gather(1, target.unsqueeze(1)).squeeze(1)
+            else:
+                output = F.log_softmax(logit, dim=-1)
         else:
             # construct weights and biases
             weights, biases = [], []
@@ -133,14 +144,17 @@ class ProjectedAdaptiveLogSoftmax(nn.Module):
             head_logit = self._compute_logit(hidden, head_weight, head_bias, head_proj)
             head_logprob = F.log_softmax(head_logit, dim=1)
 
-            nll = torch.zeros_like(target,
-                    dtype=hidden.dtype, device=hidden.device)
+            if target is None:
+                out = hidden.new_empty((head_logit.size(0), self.n_token))
+            else:
+                out = torch.zeros_like(target, dtype=hidden.dtype, device=hidden.device)
 
             offset = 0
             cutoff_values = [0] + self.cutoffs
             for i in range(len(cutoff_values) - 1):
                 l_idx, r_idx = cutoff_values[i], cutoff_values[i + 1]
 
+                if target is not None:
                     mask_i = (target >= l_idx) & (target < r_idx)
                     indices_i = mask_i.nonzero().squeeze()
 
@@ -149,28 +163,36 @@ class ProjectedAdaptiveLogSoftmax(nn.Module):
 
                     target_i = target.index_select(0, indices_i) - l_idx
                     head_logprob_i = head_logprob.index_select(0, indices_i)
+                    hidden_i = hidden.index_select(0, indices_i)
+                else:
+                    hidden_i = hidden
 
                 if i == 0:
+                    if target is not None:
                         logprob_i = head_logprob_i.gather(1, target_i[:,None]).squeeze(1)
+                    else:
+                        out[:, :self.cutoffs[0]] = head_logprob[:, :self.cutoffs[0]]
                 else:
                     weight_i, bias_i, proj_i = weights[i], biases[i], self.out_projs[i]
 
-                    hidden_i = hidden.index_select(0, indices_i)
-
                     tail_logit_i = self._compute_logit(hidden_i, weight_i, bias_i, proj_i)
                     tail_logprob_i = F.log_softmax(tail_logit_i, dim=1)
                     cluster_prob_idx = self.cutoffs[0] + i - 1  # No probability for the head cluster
+                    if target is not None:
                         logprob_i = head_logprob_i[:, cluster_prob_idx] \
                                 + tail_logprob_i.gather(1, target_i[:, None]).squeeze(1)
+                    else:
+                        logprob_i = head_logprob[:, cluster_prob_idx, None] + tail_logprob_i
+                        out[:, l_idx:r_idx] = logprob_i
 
+                if target is not None:
                     if (hasattr(self, 'keep_order') and self.keep_order) or keep_order:
-                    nll.index_copy_(0, indices_i, -logprob_i)
+                        out.index_copy_(0, indices_i, -logprob_i)
                     else:
-                    nll[offset:offset+logprob_i.size(0)].copy_(-logprob_i)
-
+                        out[offset:offset+logprob_i.size(0)].copy_(-logprob_i)
                     offset += logprob_i.size(0)
 
-        return nll
+        return out
 
 
     def log_prob(self, hidden):