Add TAPAS MLM-only models (#13408)

* Add conversion of TapasForMaskedLM

* Add copied from statements

src/transformers/__init__.py

@@ -1132,6 +1132,7 @@ if is_torch_available():
             "TapasForSequenceClassification",
             "TapasModel",
             "TapasPreTrainedModel",
+            "load_tf_weights_in_tapas",
         ]
     )
     _import_structure["models.transfo_xl"].extend(
@@ -2771,6 +2772,7 @@ if TYPE_CHECKING:
             TapasForSequenceClassification,
             TapasModel,
             TapasPreTrainedModel,
+            load_tf_weights_in_tapas,
         )
         from .models.transfo_xl import (
             TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST,

src/transformers/models/tapas/__init__.py

@@ -34,6 +34,7 @@ if is_torch_available():
         "TapasForSequenceClassification",
         "TapasModel",
         "TapasPreTrainedModel",
+        "load_tf_weights_in_tapas",
     ]
 
 
@@ -49,6 +50,7 @@ if TYPE_CHECKING:
             TapasForSequenceClassification,
             TapasModel,
             TapasPreTrainedModel,
+            load_tf_weights_in_tapas,
         )
 
 else:

src/transformers/models/tapas/convert_tapas_original_tf_checkpoint_to_pytorch.py

@@ -81,22 +81,21 @@ def convert_tf_checkpoint_to_pytorch(
         model = TapasForMaskedLM(config=config)
     elif task == "INTERMEDIATE_PRETRAINING":
         model = TapasModel(config=config)
+    else:
+        raise ValueError(f"Task {task} not supported.")
 
     print(f"Building PyTorch model from configuration: {config}")
-
     # Load weights from tf checkpoint
     load_tf_weights_in_tapas(model, config, tf_checkpoint_path)
 
     # Save pytorch-model (weights and configuration)
     print(f"Save PyTorch model to {pytorch_dump_path}")
-    model.save_pretrained(pytorch_dump_path[:-17])
+    model.save_pretrained(pytorch_dump_path)
 
     # Save tokenizer files
-    dir_name = r"C:\Users\niels.rogge\Documents\Python projecten\tensorflow\Tensorflow models\SQA\Base\tapas_sqa_inter_masklm_base_reset"
-    tokenizer = TapasTokenizer(vocab_file=dir_name + r"\vocab.txt", model_max_length=512)
-
     print(f"Save tokenizer files to {pytorch_dump_path}")
-    tokenizer.save_pretrained(pytorch_dump_path[:-17])
+    tokenizer = TapasTokenizer(vocab_file=tf_checkpoint_path[:-10] + "vocab.txt", model_max_length=512)
+    tokenizer.save_pretrained(pytorch_dump_path)
 
     print("Used relative position embeddings:", model.config.reset_position_index_per_cell)
 

src/transformers/models/tapas/modeling_tapas.py

@@ -192,6 +192,11 @@ def load_tf_weights_in_tapas(model, config, tf_checkpoint_path):
             if any(n in ["output_bias", "output_weights", "output_bias_cls", "output_weights_cls"] for n in name):
                 logger.info(f"Skipping {'/'.join(name)}")
                 continue
+        # in case the model is TapasForMaskedLM, we skip the pooler
+        if isinstance(model, TapasForMaskedLM):
+            if any(n in ["pooler"] for n in name):
+                logger.info(f"Skipping {'/'.join(name)}")
+                continue
         # if first scope name starts with "bert", change it to "tapas"
         if name[0] == "bert":
             name[0] = "tapas"
@@ -207,7 +212,10 @@ def load_tf_weights_in_tapas(model, config, tf_checkpoint_path):
                 pointer = getattr(pointer, "bias")
             # cell selection heads
             elif scope_names[0] == "output_bias":
+                if not isinstance(model, TapasForMaskedLM):
                     pointer = getattr(pointer, "output_bias")
+                else:
+                    pointer = getattr(pointer, "bias")
             elif scope_names[0] == "output_weights":
                 pointer = getattr(pointer, "output_weights")
             elif scope_names[0] == "column_output_bias":
@@ -697,6 +705,56 @@ class TapasPooler(nn.Module):
         return pooled_output
 
 
+# Copied from transformers.models.bert.modeling_bert.BertPredictionHeadTransform with Bert->Tapas
+class TapasPredictionHeadTransform(nn.Module):
+    def __init__(self, config):
+        super().__init__()
+        self.dense = nn.Linear(config.hidden_size, config.hidden_size)
+        if isinstance(config.hidden_act, str):
+            self.transform_act_fn = ACT2FN[config.hidden_act]
+        else:
+            self.transform_act_fn = config.hidden_act
+        self.LayerNorm = nn.LayerNorm(config.hidden_size, eps=config.layer_norm_eps)
+
+    def forward(self, hidden_states):
+        hidden_states = self.dense(hidden_states)
+        hidden_states = self.transform_act_fn(hidden_states)
+        hidden_states = self.LayerNorm(hidden_states)
+        return hidden_states
+
+
+# Copied from transformers.models.bert.modeling_bert.BertLMPredictionHead with Bert->Tapas
+class TapasLMPredictionHead(nn.Module):
+    def __init__(self, config):
+        super().__init__()
+        self.transform = TapasPredictionHeadTransform(config)
+
+        # The output weights are the same as the input embeddings, but there is
+        # an output-only bias for each token.
+        self.decoder = nn.Linear(config.hidden_size, config.vocab_size, bias=False)
+
+        self.bias = nn.Parameter(torch.zeros(config.vocab_size))
+
+        # Need a link between the two variables so that the bias is correctly resized with `resize_token_embeddings`
+        self.decoder.bias = self.bias
+
+    def forward(self, hidden_states):
+        hidden_states = self.transform(hidden_states)
+        hidden_states = self.decoder(hidden_states)
+        return hidden_states
+
+
+# Copied from transformers.models.bert.modeling_bert.BertOnlyMLMHead with Bert->Tapas
+class TapasOnlyMLMHead(nn.Module):
+    def __init__(self, config):
+        super().__init__()
+        self.predictions = TapasLMPredictionHead(config)
+
+    def forward(self, sequence_output):
+        prediction_scores = self.predictions(sequence_output)
+        return prediction_scores
+
+
 class TapasPreTrainedModel(PreTrainedModel):
     """
     An abstract class to handle weights initialization and a simple interface for downloading and loading pretrained
@@ -947,15 +1005,15 @@ class TapasForMaskedLM(TapasPreTrainedModel):
         super().__init__(config)
 
         self.tapas = TapasModel(config, add_pooling_layer=False)
-        self.lm_head = nn.Linear(config.hidden_size, config.vocab_size)
+        self.cls = TapasOnlyMLMHead(config)
 
         self.init_weights()
 
     def get_output_embeddings(self):
-        return self.lm_head
+        return self.cls.predictions.decoder
 
-    def set_output_embeddings(self, word_embeddings):
-        self.lm_head = word_embeddings
+    def set_output_embeddings(self, new_embeddings):
+        self.cls.predictions.decoder = new_embeddings
 
     @add_start_docstrings_to_model_forward(TAPAS_INPUTS_DOCSTRING.format("batch_size, sequence_length"))
     @replace_return_docstrings(output_type=MaskedLMOutput, config_class=_CONFIG_FOR_DOC)
@@ -1020,7 +1078,7 @@ class TapasForMaskedLM(TapasPreTrainedModel):
         )
 
         sequence_output = outputs[0]
-        prediction_scores = self.lm_head(sequence_output)
+        prediction_scores = self.cls(sequence_output)
 
         masked_lm_loss = None
         if labels is not None:

src/transformers/utils/dummy_pt_objects.py

@@ -3406,6 +3406,10 @@ class TapasPreTrainedModel:
         requires_backends(cls, ["torch"])
 
 
+def load_tf_weights_in_tapas(*args, **kwargs):
+    requires_backends(load_tf_weights_in_tapas, ["torch"])
+
+
 TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST = None