Fix loading zero3 weights (huggingface#36455)

* Check if fixes

* Fix zero3 loading

* Quality

* Fix marc nit

* Add fast tests

* Migrate to integrations.deepspeed rather than modeling_utils

* Style

src/transformers/integrations/deepspeed.py

@@ -27,6 +27,7 @@
 
 if is_torch_available():
     import torch
+    from torch import nn
 
 
 logger = logging.get_logger(__name__)
@@ -305,6 +306,57 @@ def deepspeed_config():
         return None
 
 
+def _load_state_dict_into_zero3_model(model_to_load, state_dict, start_prefix, assign_to_params_buffers=False):
+    """
+    Loads state dict into a model specifically for Zero3, since DeepSpeed does not support the `transformers`
+    tensor parallelism API.
+
+    Nearly identical code to PyTorch's `_load_from_state_dict`
+    """
+    # copy state_dict so `_load_state_dict_into_zero3_model` can modify it
+    metadata = getattr(state_dict, "_metadata", None)
+    state_dict = state_dict.copy()
+    if metadata is not None:
+        state_dict._metadata = metadata
+
+    error_msgs = []
+
+    # PyTorch's `_load_from_state_dict` does not copy parameters in a module's descendants
+    # so we need to apply the function recursively.
+    def load(module: nn.Module, state_dict, prefix="", assign_to_params_buffers=False):
+        local_metadata = {} if metadata is None else metadata.get(prefix[:-1], {})
+        local_metadata["assign_to_params_buffers"] = assign_to_params_buffers
+
+        args = (state_dict, prefix, local_metadata, True, [], [], error_msgs)
+        # Parameters of module and children will start with prefix. We can exit early if there are none in this
+        # state_dict
+        if is_deepspeed_zero3_enabled() and len([key for key in state_dict if key.startswith(prefix)]) > 0:
+            import deepspeed
+
+            # In sharded models, each shard has only part of the full state_dict, so only gather
+            # parameters that are in the current state_dict.
+            named_parameters = dict(module.named_parameters(prefix=prefix[:-1], recurse=False))
+            params_to_gather = [named_parameters[k] for k in state_dict.keys() if k in named_parameters]
+            if len(params_to_gather) > 0:
+                # because zero3 puts placeholders in model params, this context
+                # manager gathers (unpartitions) the params of the current layer, then loads from
+                # the state dict and then re-partitions them again
+                with deepspeed.zero.GatheredParameters(params_to_gather, modifier_rank=0):
+                    if torch.distributed.get_rank() == 0:
+                        module._load_from_state_dict(*args)
+
+        for name, child in module._modules.items():
+            if child is not None:
+                load(child, state_dict, prefix + name + ".", assign_to_params_buffers)
+
+    load(model_to_load, state_dict, prefix=start_prefix, assign_to_params_buffers=assign_to_params_buffers)
+    # Delete `state_dict` so it could be collected by GC earlier. Note that `state_dict` is a copy of the argument, so
+    # it's safe to delete it.
+    del state_dict
+
+    return error_msgs
+
+
 def deepspeed_optim_sched(trainer, hf_deepspeed_config, args, num_training_steps, model_parameters):
     """
     A convenience wrapper that deals with optimizer and lr scheduler configuration.

src/transformers/modeling_utils.py

@@ -50,6 +50,7 @@
 from .dynamic_module_utils import custom_object_save
 from .generation import CompileConfig, GenerationConfig, GenerationMixin
 from .integrations import PeftAdapterMixin, deepspeed_config, is_deepspeed_zero3_enabled
+from .integrations.deepspeed import _load_state_dict_into_zero3_model
 from .integrations.flash_attention import flash_attention_forward
 from .integrations.flex_attention import flex_attention_forward
 from .integrations.sdpa_attention import sdpa_attention_forward
@@ -4918,7 +4919,13 @@ def _load_pretrained_model(
                 mismatched_names = [name for name, _, _ in mismatched_keys]
                 fixed_state_dict = {k: v for k, v in state_dict.items() if k not in mismatched_names}
                 fixed_state_dict = model_to_load._fix_state_dict_keys_on_load(fixed_state_dict)
-                model_to_load.load_state_dict(fixed_state_dict, strict=False, assign=assign_to_params_buffers)
+
+                if is_deepspeed_zero3_enabled():
+                    error_msgs += _load_state_dict_into_zero3_model(
+                        model_to_load, fixed_state_dict, start_prefix, assign_to_params_buffers
+                    )
+                else:
+                    model_to_load.load_state_dict(fixed_state_dict, strict=False, assign=assign_to_params_buffers)
         else:
             # This should always be a list but, just to be sure.
             if not isinstance(resolved_archive_file, list):
@@ -5009,7 +5016,12 @@ def _load_pretrained_model(
                             model_to_load, state_dict, start_prefix
                         )
                     fixed_state_dict = model_to_load._fix_state_dict_keys_on_load(state_dict)
-                    model_to_load.load_state_dict(fixed_state_dict, strict=False, assign=assign_to_params_buffers)
+                    if is_deepspeed_zero3_enabled():
+                        error_msgs += _load_state_dict_into_zero3_model(
+                            model_to_load, fixed_state_dict, start_prefix, assign_to_params_buffers
+                        )
+                    else:
+                        model_to_load.load_state_dict(fixed_state_dict, strict=False, assign=assign_to_params_buffers)
                 # force memory release
                 del state_dict
                 gc.collect()

tests/deepspeed/test_deepspeed.py

@@ -170,7 +170,6 @@ def parameterized_custom_name_func(func, param_num, param):
 
 
 @require_deepspeed
-@require_torch_accelerator
 class CoreIntegrationDeepSpeed(TestCasePlus, TrainerIntegrationCommon):
     """
     Testing non-Trainer DeepSpeed integration
@@ -194,13 +193,52 @@ def tearDown(self):
         # reset the ds config global so that tests state doesn't leak
         unset_hf_deepspeed_config()
 
+    def test_init_zero3(self):
+        # test that zero.Init() works correctly
+        ds_config = {
+            "train_batch_size": 1,
+            "zero_optimization": {
+                "stage": 3,
+            },
+        }
+
+        dschf = HfDeepSpeedConfig(ds_config)
+
+        self.assertTrue(dschf.is_zero3())
+        self.assertTrue(is_deepspeed_zero3_enabled())
+
+        with LoggingLevel(logging.INFO):
+            with mockenv_context(**self.dist_env_1_gpu):
+                logger = logging.get_logger("transformers.modeling_utils")
+                with CaptureLogger(logger) as cl:
+                    AutoModel.from_pretrained(T5_TINY)
+        self.assertIn("Detected DeepSpeed ZeRO-3", cl.out)
+
+        # now remove zero optimization
+        del ds_config["zero_optimization"]
+        dschf = HfDeepSpeedConfig(ds_config)
+
+        self.assertFalse(dschf.is_zero3())
+        self.assertFalse(is_deepspeed_zero3_enabled())
+
+        with LoggingLevel(logging.INFO):
+            with mockenv_context(**self.dist_env_1_gpu):
+                logger = logging.get_logger("transformers.modeling_utils")
+                with CaptureLogger(logger) as cl:
+                    AutoModel.from_pretrained(T5_TINY)
+        self.assertNotIn("Detected DeepSpeed ZeRO-3", cl.out)
+
+    @require_torch_accelerator
     def test_init_zero3_fp16(self):
         # test that zero.Init() works correctly under zero3/fp16
         ds_config = {
             "train_batch_size": 1,
             "zero_optimization": {
                 "stage": 3,
             },
+            "fp16": {
+                "enabled": True,
+            },
         }
 
         dschf = HfDeepSpeedConfig(ds_config)