Fix pi0 checkpoint state map (#1415)

Co-authored-by: Michel Aractingi <michel.aractingi@huggingface.co>

src/lerobot/policies/pi0/modeling_pi0.py

@@ -66,7 +66,8 @@ from lerobot.policies.pi0.paligemma_with_expert import (
     PaliGemmaWithExpertModel,
 )
 from lerobot.policies.pretrained import PreTrainedPolicy
-from lerobot.utils.utils import get_safe_dtype
+from lerobot.policies.utils import log_model_loading_keys
+from lerobot.utils.utils import get_safe_dtype, init_logging
 
 
 def create_sinusoidal_pos_embedding(
@@ -252,6 +253,99 @@ class PI0Policy(PreTrainedPolicy):
         """This should be called whenever the environment is reset."""
         self._action_queue = deque([], maxlen=self.config.n_action_steps)
 
+    @classmethod
+    def _transform_state_dict_keys(cls, state_dict: dict) -> dict:
+        """
+        Transform state dict keys to match expected model structure.
+
+        Transformations:
+        - model.paligemma_with_expert.paligemma.language_model.lm_head ->
+          model.paligemma_with_expert.paligemma.lm_head
+        - model.paligemma_with_expert.paligemma.language_model.model ->
+          model.paligemma_with_expert.paligemma.model.language_model
+        - model.paligemma_with_expert.paligemma.vision_tower ->
+          model.paligemma_with_expert.paligemma.model.vision_tower
+        - model.paligemma_with_expert.paligemma.multi_modal_projector ->
+          model.paligemma_with_expert.paligemma.model.multi_modal_projector
+
+        Also handles tied weights between lm_head.weight and
+        embed_tokens.weight.
+        """
+        import re
+
+        transformed_dict = {}
+
+        transformations = [
+            (
+                re.compile(r"\.paligemma_with_expert\.paligemma\.language_model\.lm_head"),
+                ".paligemma_with_expert.paligemma.lm_head",
+            ),
+            (
+                re.compile(r"\.paligemma_with_expert\.paligemma\.language_model\.model"),
+                ".paligemma_with_expert.paligemma.model.language_model",
+            ),
+            (
+                re.compile(r"\.paligemma_with_expert\.paligemma\.vision_tower"),
+                ".paligemma_with_expert.paligemma.model.vision_tower",
+            ),
+            (
+                re.compile(r"\.paligemma_with_expert\.paligemma\.multi_modal_projector"),
+                ".paligemma_with_expert.paligemma.model.multi_modal_projector",
+            ),
+        ]
+
+        for key, value in state_dict.items():
+            new_key = key
+            for pattern, replacement in transformations:
+                new_key = pattern.sub(replacement, new_key)
+            transformed_dict[new_key] = value
+
+        # Handle tied weights: lm_head.weight and embed_tokens.weight share memory
+        lm_head_key = None
+        embed_tokens_key = None
+
+        for key in transformed_dict:
+            if key.endswith(".paligemma_with_expert.paligemma.lm_head.weight"):
+                lm_head_key = key
+            elif key.endswith(".paligemma_with_expert.paligemma.model.language_model.embed_tokens.weight"):
+                embed_tokens_key = key
+            if lm_head_key and embed_tokens_key:
+                break
+
+        if lm_head_key and not embed_tokens_key:
+            embed_tokens_key = lm_head_key.replace(
+                ".lm_head.weight", ".model.language_model.embed_tokens.weight"
+            )
+            transformed_dict[embed_tokens_key] = transformed_dict[lm_head_key]
+        elif embed_tokens_key and not lm_head_key:
+            lm_head_key = embed_tokens_key.replace(
+                ".model.language_model.embed_tokens.weight", ".lm_head.weight"
+            )
+            transformed_dict[lm_head_key] = transformed_dict[embed_tokens_key]
+
+        return transformed_dict
+
+    @classmethod
+    def _load_as_safetensor(
+        cls, model: "PI0Policy", model_file: str, map_location: str, strict: bool
+    ) -> "PI0Policy":
+        """Override to apply key transformations before loading."""
+        from safetensors.torch import load_file
+
+        init_logging()
+        # Load the state dict from file safely
+        state_dict = load_file(model_file, device=map_location)
+
+        # Apply key transformations
+        transformed_state_dict = cls._transform_state_dict_keys(state_dict)
+
+        # Load the transformed state dict
+        msg = model.load_state_dict(transformed_state_dict, strict=strict)
+
+        # Log message
+        log_model_loading_keys(msg.missing_keys, msg.unexpected_keys)
+        return model
+
     def get_optim_params(self) -> dict:
         return self.parameters()
 

src/lerobot/policies/pretrained.py

@@ -30,6 +30,7 @@ from torch import Tensor, nn
 
 from lerobot.configs.policies import PreTrainedConfig
 from lerobot.configs.train import TrainPipelineConfig
+from lerobot.policies.utils import log_model_loading_keys
 from lerobot.utils.hub import HubMixin
 
 T = TypeVar("T", bound="PreTrainedPolicy")
@@ -128,9 +129,19 @@ class PreTrainedPolicy(nn.Module, HubMixin, abc.ABC):
 
     @classmethod
     def _load_as_safetensor(cls, model: T, model_file: str, map_location: str, strict: bool) -> T:
-        if packaging.version.parse(safetensors.__version__) < packaging.version.parse("0.4.3"):
+        # Create base kwargs
-            load_model_as_safetensor(model, model_file, strict=strict)
+        kwargs = {"strict": strict}
-            if map_location != "cpu":
+
+        # Add device parameter for newer versions that support it
+        if packaging.version.parse(safetensors.__version__) >= packaging.version.parse("0.4.3"):
+            kwargs["device"] = map_location
+
+        # Load the model with appropriate kwargs
+        missing_keys, unexpected_keys = load_model_as_safetensor(model, model_file, **kwargs)
+        log_model_loading_keys(missing_keys, unexpected_keys)
+
+        # For older versions, manually move to device if needed
+        if "device" not in kwargs and map_location != "cpu":
             logging.warning(
                 "Loading model weights on other devices than 'cpu' is not supported natively in your version of safetensors."
                 " This means that the model is loaded on 'cpu' first and then copied to the device."
@@ -138,8 +149,6 @@ class PreTrainedPolicy(nn.Module, HubMixin, abc.ABC):
                 " Please update safetensors to version 0.4.3 or above for improved performance."
             )
             model.to(map_location)
-        else:
-            safetensors.torch.load_model(model, model_file, strict=strict, device=map_location)
         return model
 
     @abc.abstractmethod

src/lerobot/policies/utils.py

@@ -14,6 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
 from collections import deque
 
 import torch
@@ -71,3 +72,16 @@ def get_output_shape(module: nn.Module, input_shape: tuple) -> tuple:
     with torch.inference_mode():
         output = module(dummy_input)
     return tuple(output.shape)
+
+
+def log_model_loading_keys(missing_keys: list[str], unexpected_keys: list[str]) -> None:
+    """Log missing and unexpected keys when loading a model.
+
+    Args:
+        missing_keys (list[str]): Keys that were expected but not found.
+        unexpected_keys (list[str]): Keys that were found but not expected.
+    """
+    if missing_keys:
+        logging.warning(f"Missing key(s) when loading model: {missing_keys}")
+    if unexpected_keys:
+        logging.warning(f"Unexpected key(s) when loading model: {unexpected_keys}")