[FIX] resize_token_embeddings (#26102)

* fix roundup command

* add test for resize_token_embeddings

* Update tests/test_modeling_common.py
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* style

---------
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

src/transformers/modeling_utils.py

@@ -1530,7 +1530,7 @@ class PreTrainedModel(nn.Module, ModuleUtilsMixin, GenerationMixin, PushToHubMix
                 )
             if new_num_tokens is None:
                 new_num_tokens = old_embeddings.weight.shape[0]
-            new_num_tokens = ((new_num_tokens // pad_to_multiple_of) + 1) * pad_to_multiple_of
+            new_num_tokens = ((new_num_tokens + pad_to_multiple_of - 1) // pad_to_multiple_of) * pad_to_multiple_of
         else:
             logger.warning(
                 "You are resizing the embedding layer without providing a `pad_to_multiple_of` parameter. This means that the new embedding"

tests/test_modeling_common.py

@@ -1437,6 +1437,11 @@ class ModelTesterMixin:
             model_embed = model.resize_token_embeddings(model_vocab_size + 13, pad_to_multiple_of=64)
             self.assertTrue(model_embed.weight.shape[0] // 64, 0)
 
+            # Check that resizing a model to a multiple of pad_to_multiple leads to a model of exactly that size
+            target_dimension = 128
+            model_embed = model.resize_token_embeddings(target_dimension, pad_to_multiple_of=64)
+            self.assertTrue(model_embed.weight.shape[0], target_dimension)
+
             with self.assertRaisesRegex(
                 ValueError,
                 "Asking to pad the embedding matrix to a multiple of `1.3`, which is not and integer. Please make sure to pass an integer",