Persist embedding type of BART and mBART models after resize (#32242)

* fix: persist embedding type of MBartConditonalGeneration after resize

* fix: persist embedding type of BartConditonalGeneration after resize

src/transformers/models/bart/modeling_bart.py

@@ -1431,7 +1431,8 @@ class BartModel(BartPreTrainedModel):
         super().__init__(config)
 
         padding_idx, vocab_size = config.pad_token_id, config.vocab_size
-        self.shared = nn.Embedding(vocab_size, config.d_model, padding_idx)
+        embed_scale = math.sqrt(config.d_model) if config.scale_embedding else 1.0
+        self.shared = BartScaledWordEmbedding(vocab_size, config.d_model, padding_idx, embed_scale=embed_scale)
 
         self.encoder = BartEncoder(config, self.shared)
         self.decoder = BartDecoder(config, self.shared)

src/transformers/models/mbart/modeling_mbart.py

@@ -1271,7 +1271,8 @@ class MBartModel(MBartPreTrainedModel):
         super().__init__(config)
 
         padding_idx, vocab_size = config.pad_token_id, config.vocab_size
-        self.shared = nn.Embedding(vocab_size, config.d_model, padding_idx)
+        embed_scale = math.sqrt(config.d_model) if config.scale_embedding else 1.0
+        self.shared = MBartScaledWordEmbedding(vocab_size, config.d_model, padding_idx, embed_scale=embed_scale)
 
         self.encoder = MBartEncoder(config, self.shared)
         self.decoder = MBartDecoder(config, self.shared)

tests/models/bart/test_modeling_bart.py

@@ -518,6 +518,18 @@ class BartModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMixin
     def test_load_save_without_tied_weights(self):
         pass
 
+    def test_resize_embeddings_persists_embeddings_type(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs()
+
+        config.scale_embedding = True
+        model = BartForConditionalGeneration(config)
+        old_type = type(model.model.decoder.embed_tokens)
+
+        model.resize_token_embeddings(new_num_tokens=config.vocab_size)
+
+        new_type = type(model.model.decoder.embed_tokens)
+        self.assertIs(old_type, new_type)
+
 
 def assert_tensors_close(a, b, atol=1e-12, prefix=""):
     """If tensors have different shapes, different values or a and b are not both tensors, raise a nice Assertion error."""

tests/models/mbart/test_modeling_mbart.py

@@ -375,6 +375,18 @@ class MBartModelTest(ModelTesterMixin, GenerationTesterMixin, PipelineTesterMixi
     def test_load_save_without_tied_weights(self):
         pass
 
+    def test_resize_embeddings_persists_embeddings_type(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs()
+
+        config.scale_embedding = True
+        model = MBartForConditionalGeneration(config)
+        old_type = type(model.model.decoder.embed_tokens)
+
+        model.resize_token_embeddings(new_num_tokens=config.vocab_size)
+
+        new_type = type(model.model.decoder.embed_tokens)
+        self.assertIs(old_type, new_type)
+
 
 def assert_tensors_close(a, b, atol=1e-12, prefix=""):
     """If tensors have different shapes, different values or a and b are not both tensors, raise a nice Assertion error."""