Making sure we can use safetensors to serialize all the time. (#22437)

* Making sure we can use safetensors to serialize all the time.

* Expanding the tests for increased coverage.

* Update the test.

* Getting current state of affairs.

* Tentative fix.

* Fixing black version.

* Fixing the worst offenders.

* Try to modify less files.

* Fixing blip_2 (Weird solution right now).

* Fixing deta.

* Fix blip ?

* Missing extra newline.

* No deta modification.

* Adding some comments.

* Apply suggestions from code review

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* Addressing comments.

* Addressing comments.

* creating warn_once.

* Warning_once !

---------

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

src/transformers/modeling_utils.py

@@ -1736,6 +1736,41 @@ def save_pretrained(
             for ignore_key in self._keys_to_ignore_on_save:
                 if ignore_key in state_dict.keys():
                     del state_dict[ignore_key]
+        if safe_serialization:
+            # Safetensors does not allow tensor aliasing.
+            # We're going to remove aliases before saving
+            ptrs = collections.defaultdict(list)
+            for name, tensor in state_dict.items():
+                ptrs[tensor.data_ptr()].append(name)
+
+            # These are all the pointers of shared tensors.
+            shared_ptrs = {ptr: names for ptr, names in ptrs.items() if len(names) > 1}
+            warn_names = set()
+            for names in shared_ptrs.values():
+                # Removing the keys which are declared as known duplicates on
+                # load. This allows to make sure the name which is kept is consistent.
+                if self._keys_to_ignore_on_load_missing is not None:
+                    for name in names:
+                        matches_pattern = any(re.search(pat, name) for pat in self._keys_to_ignore_on_load_missing)
+                        if matches_pattern and name in state_dict:
+                            del state_dict[name]
+
+                # When not all duplicates have been cleaned, still remove those keys, but put a clear warning.
+                # If the link between tensors was done at runtime then `from_pretrained` will not get
+                # the key back leading to random tensor. A proper warning will be shown
+                # during reload (if applicable), but since the file is not necessarily compatible with
+                # the config, better show a proper warning.
+                found = 0
+                for name in names:
+                    if name in state_dict:
+                        found += 1
+                        if found > 1:
+                            del state_dict[name]
+                            warn_names.add(name)
+            if len(warn_names) > 0:
+                logger.warning_once(
+                    f"Removed shared tensor {warn_names} while saving. This should be OK, but check by verifying that you don't receive any warning while reloading",
+                )
 
         # Shard the model if it is too big.
         weights_name = SAFE_WEIGHTS_NAME if safe_serialization else WEIGHTS_NAME
@@ -2813,6 +2848,11 @@ def _fix_key(key):
         missing_keys = list(set(expected_keys) - set(loaded_keys))
         unexpected_keys = list(set(loaded_keys) - set(expected_keys))
 
+        # Some tensors maybe have been already filled by another key (tied weights).
+        existing_ptrs = {model_state_dict[k].data_ptr() for k in loaded_keys if k in model_state_dict}
+        missing_keys = [
+            k for k in missing_keys if k in model_state_dict and model_state_dict[k].data_ptr() not in existing_ptrs
+        ]
         # Some models may have keys that are not in the state by design, removing them before needlessly warning
         # the user.
         if cls._keys_to_ignore_on_load_missing is not None:

src/transformers/models/blip_2/modeling_blip_2.py

@@ -1238,8 +1238,28 @@ def __init__(self, config: Blip2Config):
         # Initialize weights and apply final processing
         self.post_init()
 
-    def get_input_embeddings(self) -> nn.Module:
-        return self.vision_model.embeddings.patch_embedding
+    def get_input_embeddings(self):
+        return self.language_model.get_input_embeddings()
+
+    def set_input_embeddings(self, value):
+        self.language_model.set_input_embeddings(value)
+
+    def set_output_embeddings(self, new_embeddings):
+        self.language_model.set_output_embeddings(new_embeddings)
+
+    def get_output_embeddings(self) -> nn.Module:
+        return self.language_model.get_output_embeddings()
+
+    def get_encoder(self):
+        return self.language_model.get_encoder()
+
+    def get_decoder(self):
+        return self.language_model.get_decoder()
+
+    def _tie_weights(self):
+        if not self.config.use_decoder_only_language_model:
+            self.language_model.encoder.embed_tokens = self.language_model.shared
+            self.language_model.decoder.embed_tokens = self.language_model.shared
 
     @add_start_docstrings_to_model_forward(BLIP_2_TEXT_INPUTS_DOCSTRING)
     def get_text_features(

src/transformers/models/deta/modeling_deta.py

@@ -244,7 +244,7 @@ class DetaObjectDetectionOutput(ModelOutput):
 
 
 def _get_clones(module, N):
-    return nn.ModuleList([copy.deepcopy(module) for i in range(N)])
+    return nn.ModuleList([module for i in range(N)])
 
 
 def inverse_sigmoid(x, eps=1e-5):

src/transformers/models/llama/modeling_llama.py

@@ -609,8 +609,6 @@ def custom_forward(*inputs):
 
 
 class LlamaForCausalLM(LlamaPreTrainedModel):
-    _keys_to_ignore_on_load_missing = [r"lm_head.weight"]
-
     def __init__(self, config):
         super().__init__(config)
         self.model = LlamaModel(config)

src/transformers/models/pix2struct/configuration_pix2struct.py

@@ -357,9 +357,10 @@ def __init__(
         initializer_factor=1.0,
         initializer_range=0.02,
         is_vqa=False,
+        tie_word_embeddings=False,
         **kwargs,
     ):
-        super().__init__(**kwargs)
+        super().__init__(tie_word_embeddings=tie_word_embeddings, **kwargs)
 
         if text_config is None:
             text_config = {}

tests/test_modeling_common.py

@@ -27,6 +27,7 @@
 import unittest
 import unittest.mock as mock
 import warnings
+from collections import defaultdict
 from pathlib import Path
 from typing import Dict, List, Tuple
 
@@ -1626,6 +1627,41 @@ def check_same_values(layer_1, layer_2):
             # self.assertTrue(model.transformer.wte.weight.shape, model.lm_head.weight.shape)
             # self.assertTrue(check_same_values(model.transformer.wte, model.lm_head))
 
+    @require_safetensors
+    def test_can_use_safetensors(self):
+        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+        for model_class in self.all_model_classes:
+            model_tied = model_class(config)
+            with tempfile.TemporaryDirectory() as d:
+                try:
+                    model_tied.save_pretrained(d, safe_serialization=True)
+                except Exception as e:
+                    raise Exception(f"Class {model_class.__name__} cannot be saved using safetensors: {e}")
+
+                model_reloaded, infos = model_class.from_pretrained(d, output_loading_info=True)
+                # Checking the state dicts are correct
+                reloaded_state = model_reloaded.state_dict()
+                for k, v in model_tied.state_dict().items():
+                    self.assertIn(k, reloaded_state, f"Key {k} is missing from reloaded")
+                    torch.testing.assert_close(
+                        v, reloaded_state[k], msg=lambda x: f"{model_class.__name__}: Tensor {k}: {x}"
+                    )
+
+                # Checking the tensor sharing are correct
+                ptrs = defaultdict(list)
+                for k, v in model_tied.state_dict().items():
+                    ptrs[v.data_ptr()].append(k)
+
+                shared_ptrs = {k: v for k, v in ptrs.items() if len(v) > 1}
+
+                for _, shared_names in shared_ptrs.items():
+                    reloaded_ptrs = {reloaded_state[k].data_ptr() for k in shared_names}
+                    self.assertEqual(
+                        len(reloaded_ptrs),
+                        1,
+                        f"The shared pointers are incorrect, found different pointers for keys {shared_names}",
+                    )
+
     def test_tied_model_weights_key_ignore(self):
         config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
         for model_class in self.all_model_classes: