Add head_mask, decoder_head_mask, cross_head_mask to ProphetNet

src/transformers/models/prophetnet/modeling_prophetnet.py

@@ -104,6 +104,24 @@
         decoder_attention_mask (:obj:`torch.BoolTensor` of shape :obj:`(batch_size, target_sequence_length)`, `optional`):
             Default behavior: generate a tensor that ignores pad tokens in :obj:`decoder_input_ids`. Causal mask will
             also be used by default.
+        head_mask (:obj:`torch.Tensor` of shape :obj:`(encoder_layers, encoder_attention_heads)`, `optional`):
+            Mask to nullify selected heads of the attention modules in the encoder. Mask values selected in ``[0, 1]``:
+
+            - 1 indicates the head is **not masked**,
+            - 0 indicates the head is **masked**.
+
+        decoder_head_mask (:obj:`torch.Tensor` of shape :obj:`(decoder_layers, decoder_attention_heads)`, `optional`):
+            Mask to nullify selected heads of the attention modules in the decoder. Mask values selected in ``[0, 1]``:
+
+            - 1 indicates the head is **not masked**,
+            - 0 indicates the head is **masked**.
+
+        cross_attn_head_mask (:obj:`torch.Tensor` of shape :obj:`(decoder_layers, decoder_attention_heads)`, `optional`):
+            Mask to nullify selected heads of the cross-attention modules. Mask values selected in ``[0, 1]``:
+
+            - 1 indicates the head is **not masked**,
+            - 0 indicates the head is **masked**.
+
         encoder_outputs (:obj:`tuple(tuple(torch.FloatTensor)`, `optional`):
             Tuple consists of (:obj:`last_hidden_state`, `optional`: :obj:`hidden_states`, `optional`:
             :obj:`attentions`) :obj:`last_hidden_state` of shape :obj:`(batch_size, sequence_length, hidden_size)`,
@@ -146,6 +164,12 @@
             - 0 for tokens that are **masked**.
 
             `What are attention masks? <../glossary.html#attention-mask>`__
+        head_mask (:obj:`torch.Tensor` of shape :obj:`(encoder_layers, encoder_attention_heads)`, `optional`):
+            Mask to nullify selected heads of the attention modules in the encoder. Mask values selected in ``[0, 1]``:
+
+            - 1 indicates the head is **not masked**,
+            - 0 indicates the head is **masked**.
+
         output_attentions (:obj:`bool`, `optional`):
             Whether or not to return the attentions tensors of all attention layers. See ``attentions`` under returned
             tensors for more detail.
@@ -633,6 +657,7 @@ def forward(
         hidden_states,
         key_value_states: Optional[Tensor] = None,
         attention_mask: Optional[Tensor] = None,
+        layer_head_mask: Optional[Tensor] = None,
         past_key_value: Optional[Tuple[Tensor]] = None,
         output_attentions: bool = False,
     ) -> Tuple[Tensor, Optional[Tensor]]:
@@ -708,6 +733,19 @@ def forward(
             attn_weights_reshaped = None
 
         attn_weights = F.softmax(attn_weights, dim=-1)
+
+        if layer_head_mask is not None:
+            assert layer_head_mask.size() == (
+                self.num_attn_heads,
+            ), f"Head mask for a single layer should be of size {(self.num_attn_heads,)}, but is {layer_head_mask.size()}"
+            attn_weights = layer_head_mask.view(1, -1, 1, 1) * attn_weights.view(
+                batch_size, self.num_attn_heads, tgt_len, src_len
+            )
+            attn_weights = attn_weights.view(batch_size * self.num_attn_heads, tgt_len, src_len)
+
+            # apply head_mask also on attn_weights_reshaped which is used for n-gram attention inside the model
+            attn_weights_reshaped = layer_head_mask.view(1, -1, 1, 1) * attn_weights_reshaped
+
         attn_probs = F.dropout(
             attn_weights,
             p=self.attention_dropout,
@@ -797,6 +835,7 @@ def forward(
         hidden_states,
         past_key_value: Optional[Tuple[Tensor]] = None,
         attention_mask=None,
+        layer_head_mask=None,
         extended_predict_attention_mask=None,
         main_relative_position_buckets=None,
         predict_relative_position_buckets=None,
@@ -876,6 +915,15 @@ def forward(
             onnx_trace=self.onnx_trace,
         ).type_as(main_attn_weights)
 
+        if layer_head_mask is not None:
+            assert layer_head_mask.size() == (
+                self.num_attn_heads,
+            ), f"Head mask for a single layer should be of size {(self.num_attn_heads,)}, but is {layer_head_mask.size()}"
+            main_attn_probs = layer_head_mask.view(1, -1, 1, 1) * main_attn_probs.view(
+                batch_size, self.num_attn_heads, -1, sequence_length
+            )
+            main_attn_probs = main_attn_probs.view(batch_size * self.num_attn_heads, -1, sequence_length)
+
         main_attn_probs = F.dropout(main_attn_probs, p=self.attention_dropout, training=self.training)
         # project to attn_output
         main_attn_output = torch.bmm(main_attn_probs, main_value_states)
@@ -929,6 +977,18 @@ def forward(
             dim=-1,
             onnx_trace=self.onnx_trace,
         ).type_as(predict_attn_weights)
+
+        if layer_head_mask is not None:
+            assert layer_head_mask.size() == (
+                self.num_attn_heads,
+            ), f"Head mask for a single layer should be of size {(self.num_attn_heads,)}, but is {layer_head_mask.size()}"
+            predict_attn_probs = layer_head_mask.view(1, 1, -1, 1, 1) * predict_attn_probs.view(
+                self.ngram, batch_size, self.num_attn_heads, sequence_length, 2 * sequence_length
+            )
+            predict_attn_probs = predict_attn_probs.view(
+                self.ngram, batch_size * self.num_attn_heads, sequence_length, 2 * sequence_length
+            )
+
         predict_attn_probs = F.dropout(predict_attn_probs, p=self.attention_dropout, training=self.training)
         # project to attention output
         # [ngram, B*head, T, c]
@@ -1063,11 +1123,18 @@ def __init__(self, config: ProphetNetConfig):
         self.feed_forward = ProphetNetFeedForward(config, config.encoder_ffn_dim)
         self.feed_forward_layer_norm = LayerNorm(config.hidden_size)
 
-    def forward(self, hidden_states, attention_mask, output_attentions: bool = False):
+    def forward(
+        self,
+        hidden_states,
+        attention_mask,
+        layer_head_mask,
+        output_attentions: bool = False,
+    ):
         # 1st residual block
         attention_output, attn_weights, _ = self.self_attn(
             hidden_states=hidden_states,
             attention_mask=attention_mask,
+            layer_head_mask=layer_head_mask,
             output_attentions=output_attentions,
         )
         hidden_states = self.self_attn_layer_norm(attention_output + hidden_states)
@@ -1110,6 +1177,8 @@ def forward(
         attention_mask=None,
         encoder_hidden_states=None,
         encoder_attn_mask=None,
+        layer_head_mask=None,
+        cross_attn_layer_head_mask=None,
         extended_predict_attention_mask=None,
         main_relative_position_buckets=None,
         predict_relative_position_buckets=None,
@@ -1125,6 +1194,7 @@ def forward(
             hidden_states=hidden_states,
             past_key_value=self_attn_past_key_value,
             attention_mask=attention_mask,
+            layer_head_mask=layer_head_mask,
             extended_predict_attention_mask=extended_predict_attention_mask,
             main_relative_position_buckets=main_relative_position_buckets,
             predict_relative_position_buckets=predict_relative_position_buckets,
@@ -1141,6 +1211,7 @@ def forward(
                 hidden_states=hidden_states,
                 key_value_states=encoder_hidden_states,
                 attention_mask=encoder_attn_mask,
+                layer_head_mask=cross_attn_layer_head_mask,
                 past_key_value=cross_attn_past_key_value,
                 output_attentions=output_attentions,
             )
@@ -1202,6 +1273,7 @@ def forward(
         self,
         input_ids=None,
         attention_mask=None,
+        head_mask=None,
         inputs_embeds=None,
         output_attentions=None,
         output_hidden_states=None,
@@ -1254,7 +1326,12 @@ def forward(
         encoder_hidden_states = () if output_hidden_states else None
         all_attentions = () if output_attentions else None
 
-        for encoder_layer in self.layers:
+        # check if head_mask has a correct number of layers specified if desired
+        if head_mask is not None:
+            assert head_mask.size()[0] == (
+                len(self.layers)
+            ), f"The head_mask should be specified for {len(self.layers)} layers, but it is for {head_mask.size()[0]}."
+        for idx, encoder_layer in enumerate(self.layers):
             if output_hidden_states:
                 encoder_hidden_states = encoder_hidden_states + (hidden_states,)
 
@@ -1270,10 +1347,14 @@ def custom_forward(*inputs):
                     create_custom_forward(encoder_layer),
                     hidden_states,
                     extended_attention_mask,
+                    (head_mask[idx] if head_mask is not None else None),
                 )
             else:
                 layer_outputs = encoder_layer(
-                    hidden_states, attention_mask=extended_attention_mask, output_attentions=output_attentions
+                    hidden_states,
+                    attention_mask=extended_attention_mask,
+                    layer_head_mask=(head_mask[idx] if head_mask is not None else None),
+                    output_attentions=output_attentions,
                 )
 
             hidden_states = layer_outputs[0]
@@ -1338,6 +1419,8 @@ def forward(
         attention_mask=None,
         encoder_hidden_states=None,
         encoder_attention_mask=None,
+        head_mask=None,
+        cross_attn_head_mask=None,
         past_key_values=None,
         inputs_embeds=None,
         use_cache=None,
@@ -1352,6 +1435,12 @@ def forward(
         encoder_attention_mask (:obj:`torch.FloatTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
             Mask to avoid performing attention on the padding token indices of the encoder input. This mask is used in
             the cross-attention if the model is configured as a decoder. Mask values selected in ``[0, 1]``:
+        cross_attn_head_mask (:obj:`torch.Tensor` of shape :obj:`(decoder_layers, decoder_attention_heads)`, `optional`):
+            Mask to nullify selected heads of the cross-attention modules. Mask values selected in ``[0, 1]``:
+
+            - 1 indicates the head is **not masked**,
+            - 0 indicates the head is **masked**.
+
         past_key_values (:obj:`tuple(tuple(torch.FloatTensor))` of length :obj:`config.n_layers` with each tuple having 4 tensors of shape :obj:`(batch_size, num_heads, sequence_length - 1, embed_size_per_head)`):
             Contains precomputed key and value hidden-states of the attention blocks. Can be used to speed up decoding.
 
@@ -1460,6 +1549,12 @@ def forward(
         all_cross_attns = () if output_attentions and self.config.add_cross_attention else None
         present_key_values = () if use_cache else None
 
+        # check if head_mask/cross_attn_head_mask has a correct number of layers specified if desired
+        for attn_mask, mask_name in zip([head_mask, cross_attn_head_mask], ["head_mask", "cross_attn_head_mask"]):
+            if attn_mask is not None:
+                assert attn_mask.size()[0] == (
+                    len(self.layers)
+                ), f"The `{mask_name}` should be specified for {len(self.layers)} layers, but it is for {head_mask.size()[0]}."
         for idx, decoder_layer in enumerate(self.layers):
             if output_hidden_states:
                 # grad cannot be kept because tensor is sliced
@@ -1491,6 +1586,8 @@ def custom_forward(*inputs):
                     extended_attention_mask,
                     encoder_hidden_states,
                     extended_encoder_attention_mask,
+                    (head_mask[idx] if head_mask is not None else None),
+                    (cross_attn_head_mask[idx] if cross_attn_head_mask is not None else None),
                     extended_predict_attention_mask,
                     main_relative_position_buckets,
                     predict_relative_position_buckets,
@@ -1503,6 +1600,10 @@ def custom_forward(*inputs):
                     attention_mask=extended_attention_mask,
                     encoder_hidden_states=encoder_hidden_states,
                     encoder_attn_mask=extended_encoder_attention_mask,
+                    layer_head_mask=(head_mask[idx] if head_mask is not None else None),
+                    cross_attn_layer_head_mask=(
+                        cross_attn_head_mask[idx] if cross_attn_head_mask is not None else None
+                    ),
                     extended_predict_attention_mask=extended_predict_attention_mask,
                     main_relative_position_buckets=main_relative_position_buckets,
                     predict_relative_position_buckets=predict_relative_position_buckets,
@@ -1678,6 +1779,9 @@ def forward(
         attention_mask=None,
         decoder_input_ids=None,
         decoder_attention_mask=None,
+        head_mask=None,
+        decoder_head_mask=None,
+        cross_attn_head_mask=None,
         encoder_outputs: Optional[Tuple] = None,
         past_key_values=None,
         inputs_embeds=None,
@@ -1716,6 +1820,7 @@ def forward(
             encoder_outputs = self.encoder(
                 input_ids=input_ids,
                 attention_mask=attention_mask,
+                head_mask=head_mask,
                 inputs_embeds=inputs_embeds,
                 output_attentions=output_attentions,
                 output_hidden_states=output_hidden_states,
@@ -1728,6 +1833,8 @@ def forward(
             attention_mask=decoder_attention_mask,
             encoder_hidden_states=encoder_outputs[0],
             encoder_attention_mask=attention_mask,
+            head_mask=decoder_head_mask,
+            cross_attn_head_mask=cross_attn_head_mask,
             past_key_values=past_key_values,
             inputs_embeds=decoder_inputs_embeds,
             output_attentions=output_attentions,
@@ -1785,6 +1892,9 @@ def forward(
         attention_mask=None,
         decoder_input_ids=None,
         decoder_attention_mask=None,
+        head_mask=None,
+        decoder_head_mask=None,
+        cross_attn_head_mask=None,
         encoder_outputs=None,
         past_key_values=None,
         inputs_embeds=None,
@@ -1828,6 +1938,9 @@ def forward(
             attention_mask=attention_mask,
             decoder_input_ids=decoder_input_ids,
             decoder_attention_mask=decoder_attention_mask,
+            head_mask=head_mask,
+            decoder_head_mask=decoder_head_mask,
+            cross_attn_head_mask=cross_attn_head_mask,
             encoder_outputs=encoder_outputs,
             past_key_values=past_key_values,
             inputs_embeds=inputs_embeds,
@@ -1902,7 +2015,14 @@ def _compute_loss(self, logits, labels, ignore_index=-100):
         return loss
 
     def prepare_inputs_for_generation(
-        self, decoder_input_ids, past=None, attention_mask=None, use_cache=None, encoder_outputs=None, **kwargs
+        self,
+        decoder_input_ids,
+        past=None,
+        attention_mask=None,
+        head_mask=None,
+        use_cache=None,
+        encoder_outputs=None,
+        **kwargs,
     ):
         assert encoder_outputs is not None, "`encoder_outputs` have to be passed for generation."
 
@@ -1915,6 +2035,7 @@ def prepare_inputs_for_generation(
             "past_key_values": past,
             "decoder_input_ids": decoder_input_ids,
             "attention_mask": attention_mask,
+            "head_mask": head_mask,
             "use_cache": use_cache,
         }
 
@@ -1985,6 +2106,8 @@ def forward(
         attention_mask=None,
         encoder_hidden_states=None,
         encoder_attention_mask=None,
+        head_mask=None,
+        cross_attn_head_mask=None,
         past_key_values=None,
         inputs_embeds=None,
         labels=None,
@@ -2000,6 +2123,12 @@ def forward(
         encoder_attention_mask (:obj:`torch.FloatTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
             Mask to avoid performing attention on the padding token indices of the encoder input. This mask is used in
             the cross-attention if the model is configured as a decoder. Mask values selected in ``[0, 1]``:
+        cross_attn_head_mask (:obj:`torch.Tensor` of shape :obj:`(decoder_layers, decoder_attention_heads)`, `optional`):
+            Mask to nullify selected heads of the cross-attention modules. Mask values selected in ``[0, 1]``:
+
+            - 1 indicates the head is **not masked**,
+            - 0 indicates the head is **masked**.
+
         past_key_values (:obj:`tuple(tuple(torch.FloatTensor))` of length :obj:`config.n_layers` with each tuple having 4 tensors of shape :obj:`(batch_size, num_heads, sequence_length - 1, embed_size_per_head)`):
             Contains precomputed key and value hidden-states of the attention blocks. Can be used to speed up decoding.
 
@@ -2060,6 +2189,8 @@ def forward(
             attention_mask=attention_mask,
             encoder_hidden_states=encoder_hidden_states,
             encoder_attention_mask=encoder_attention_mask,
+            head_mask=head_mask,
+            cross_attn_head_mask=cross_attn_head_mask,
             past_key_values=past_key_values,
             inputs_embeds=inputs_embeds,
             use_cache=use_cache,
@@ -2123,7 +2254,15 @@ def _compute_loss(self, logits, labels, ignore_index=-100):
 
         return loss
 
-    def prepare_inputs_for_generation(self, input_ids, past=None, attention_mask=None, use_cache=None, **kwargs):
+    def prepare_inputs_for_generation(
+        self,
+        input_ids,
+        past=None,
+        attention_mask=None,
+        head_mask=None,
+        use_cache=None,
+        **kwargs,
+    ):
         # if model is used as a decoder in encoder-decoder model, the decoder attention mask is created on the fly
         if attention_mask is None:
             attention_mask = input_ids.new_ones(input_ids.shape)
@@ -2134,6 +2273,7 @@ def prepare_inputs_for_generation(self, input_ids, past=None, attention_mask=Non
         return {
             "input_ids": input_ids,  # encoder_outputs is defined. input_ids not needed
             "attention_mask": attention_mask,
+            "head_mask": head_mask,
             "past_key_values": past,
             "use_cache": use_cache,
         }

tests/test_modeling_prophetnet.py

@@ -891,7 +891,6 @@ class ProphetNetModelTest(ModelTesterMixin, GenerationTesterMixin, unittest.Test
     test_pruning = False
     test_torchscript = False
     test_resize_embeddings = False
-    test_headmasking = False
     is_encoder_decoder = True
 
     def setUp(self):
@@ -1097,7 +1096,6 @@ class ProphetNetStandaloneDecoderModelTest(ModelTesterMixin, GenerationTesterMix
     test_pruning = False
     test_torchscript = False
     test_resize_embeddings = False
-    test_headmasking = False
     is_encoder_decoder = False
 
     def setUp(self):
@@ -1126,7 +1124,6 @@ class ProphetNetStandaloneEncoderModelTest(ModelTesterMixin, unittest.TestCase):
     test_pruning = False
     test_torchscript = False
     test_resize_embeddings = False
-    test_headmasking = False
     is_encoder_decoder = False
 
     def setUp(self):