register custom_op for fpEBC (#2067)

Summary:
Pull Request resolved: #2067

# context
* convert `FeatureProcessedEmbeddingBagCollection` to custom op in IR export
* add serialization and deserialization function for FPEBC
* add an API for the `FeatureProcessorInterface` to export necessary paramters for create an instance
* use this API (`get_init_kwargs`) in the serialize and deserialize functions to flatten and unflatten the feature processor

# details
1. Added `FPEBCMetadata` schema for FP_EBC, use a `fp_json` string to store the necessary paramters
2. Added `FPEBCJsonSerializer`, converted the init_kwargs to json string and store in the `fp_json` field in the metadata
3. Added a fqn check for `serialized_fqns`, so that when a higher-level module is serialized, the lower-level module can be skipped (it's already included in the higher-level module)
4. Added an API called `get_init_kwargs` for `FeatureProcessorsCollection` and `FeatureProcessor`, and use a `FeatureProcessorNameMap` to map the classname to the feature processor class
5. Added `_non_strict_exporting_forward` function for FPEBC so that in non_strict IR export it goes to the custom_op logic

Differential Revision: D57829276

Author: TroyGarden

torchrec/ir/schema.py

@@ -8,7 +8,7 @@
 # pyre-strict
 
 from dataclasses import dataclass
-from typing import List, Optional
+from typing import List, Optional, Tuple
 
 from torchrec.modules.embedding_configs import DataType, PoolingType
 
@@ -32,3 +32,19 @@ class EBCMetadata:
     tables: List[EmbeddingBagConfigMetadata]
     is_weighted: bool
     device: Optional[str]
+
+
+@dataclass
+class FPEBCMetadata:
+    is_fp_collection: bool
+    feature_list: List[str]
+
+
+@dataclass
+class PositionWeightedModuleMetadata:
+    max_feature_length: int
+
+
+@dataclass
+class PositionWeightedModuleCollectionMetadata:
+    max_feature_lengths: List[Tuple[str, int]]

torchrec/ir/serializer.py

@@ -14,11 +14,24 @@
 import torch
 
 from torch import nn
-from torchrec.ir.schema import EBCMetadata, EmbeddingBagConfigMetadata
+from torchrec.ir.schema import (
+    EBCMetadata,
+    EmbeddingBagConfigMetadata,
+    FPEBCMetadata,
+    PositionWeightedModuleCollectionMetadata,
+    PositionWeightedModuleMetadata,
+)
 
 from torchrec.ir.types import SerializerInterface
 from torchrec.modules.embedding_configs import DataType, EmbeddingBagConfig, PoolingType
 from torchrec.modules.embedding_modules import EmbeddingBagCollection
+from torchrec.modules.feature_processor_ import (
+    FeatureProcessor,
+    FeatureProcessorsCollection,
+    PositionWeightedModule,
+    PositionWeightedModuleCollection,
+)
+from torchrec.modules.fp_embedding_modules import FeatureProcessedEmbeddingBagCollection
 
 logger: logging.Logger = logging.getLogger(__name__)
 
@@ -71,7 +84,7 @@ def get_deserialized_device(
 
 class EBCJsonSerializer(SerializerInterface):
     """
-    Serializer for torch.export IR using thrift.
+    Serializer for torch.export IR using json.
     """
 
     @classmethod
@@ -132,13 +145,155 @@ def deserialize(
         )
 
 
+class PWMJsonSerializer(SerializerInterface):
+    """
+    Serializer for torch.export IR using json.
+    """
+
+    @classmethod
+    def serialize(cls, module: nn.Module) -> torch.Tensor:
+        if not isinstance(module, PositionWeightedModule):
+            raise ValueError(
+                f"Expected module to be of type PositionWeightedModule, got {type(module)}"
+            )
+        metadata = PositionWeightedModuleMetadata(
+            max_feature_length=module.position_weight.shape[0],
+        )
+        return torch.frombuffer(
+            json.dumps(metadata.__dict__).encode(), dtype=torch.uint8
+        )
+
+    @classmethod
+    def deserialize(
+        cls,
+        input: torch.Tensor,
+        typename: str,
+        device: Optional[torch.device] = None,
+        children: Dict[str, nn.Module] = {},
+    ) -> nn.Module:
+        if typename != "PositionWeightedModule":
+            raise ValueError(
+                f"Expected typename to be PositionWeightedModule, got {typename}"
+            )
+        raw_bytes = input.numpy().tobytes()
+        metadata = json.loads(raw_bytes)
+        return PositionWeightedModule(metadata["max_feature_length"], device)
+
+
+class PWMCJsonSerializer(SerializerInterface):
+    """
+    Serializer for torch.export IR using json.
+    """
+
+    @classmethod
+    def serialize(cls, module: nn.Module) -> torch.Tensor:
+        if not isinstance(module, PositionWeightedModuleCollection):
+            raise ValueError(
+                f"Expected module to be of type PositionWeightedModuleCollection, got {type(module)}"
+            )
+        metadata = PositionWeightedModuleCollectionMetadata(
+            max_feature_lengths=[  # convert to list of tuples to preserve the order
+                (feature, len) for feature, len in module.max_feature_lengths.items()
+            ],
+        )
+        return torch.frombuffer(
+            json.dumps(metadata.__dict__).encode(), dtype=torch.uint8
+        )
+
+    @classmethod
+    def deserialize(
+        cls,
+        input: torch.Tensor,
+        typename: str,
+        device: Optional[torch.device] = None,
+        children: Dict[str, nn.Module] = {},
+    ) -> nn.Module:
+        if typename != "PositionWeightedModuleCollection":
+            raise ValueError(
+                f"Expected typename to be PositionWeightedModuleCollection, got {typename}"
+            )
+        raw_bytes = input.numpy().tobytes()
+        metadata = PositionWeightedModuleCollectionMetadata(**json.loads(raw_bytes))
+        max_feature_lengths = {
+            feature: len for feature, len in metadata.max_feature_lengths
+        }
+        return PositionWeightedModuleCollection(max_feature_lengths, device)
+
+
+class FPEBCJsonSerializer(SerializerInterface):
+    """
+    Serializer for torch.export IR using json.
+    """
+
+    @classmethod
+    def requires_children(cls, typename: str) -> bool:
+        return True
+
+    @classmethod
+    def serialize(
+        cls,
+        module: nn.Module,
+    ) -> torch.Tensor:
+        if not isinstance(module, FeatureProcessedEmbeddingBagCollection):
+            raise ValueError(
+                f"Expected module to be of type FeatureProcessedEmbeddingBagCollection, got {type(module)}"
+            )
+        elif isinstance(module._feature_processors, FeatureProcessorsCollection):
+            metadata = FPEBCMetadata(
+                is_fp_collection=True,
+                feature_list=[],
+            )
+        else:
+            metadata = FPEBCMetadata(
+                is_fp_collection=False,
+                feature_list=list(module._feature_processors.keys()),
+            )
+
+        return torch.frombuffer(
+            json.dumps(metadata.__dict__).encode(), dtype=torch.uint8
+        )
+
+    @classmethod
+    def deserialize(
+        cls,
+        input: torch.Tensor,
+        typename: str,
+        device: Optional[torch.device] = None,
+        children: Dict[str, nn.Module] = {},
+    ) -> nn.Module:
+        if typename != "FeatureProcessedEmbeddingBagCollection":
+            raise ValueError(
+                f"Expected typename to be EmbeddingBagCollection, got {typename}"
+            )
+        raw_bytes = input.numpy().tobytes()
+        metadata = FPEBCMetadata(**json.loads(raw_bytes.decode()))
+        if metadata.is_fp_collection:
+            feature_processors = children["_feature_processors"]
+            assert isinstance(feature_processors, FeatureProcessorsCollection)
+        else:
+            feature_processors: dict[str, FeatureProcessor] = {}
+            for feature in metadata.feature_list:
+                fp = children[f"_feature_processors.{feature}"]
+                assert isinstance(fp, FeatureProcessor)
+                feature_processors[feature] = fp
+        ebc = children["_embedding_bag_collection"]
+        assert isinstance(ebc, EmbeddingBagCollection)
+        return FeatureProcessedEmbeddingBagCollection(
+            ebc,
+            feature_processors,
+        )
+
+
 class JsonSerializer(SerializerInterface):
     """
-    Serializer for torch.export IR using thrift.
+    Serializer for torch.export IR using json.
     """
 
     module_to_serializer_cls: Dict[str, Type[SerializerInterface]] = {
         "EmbeddingBagCollection": EBCJsonSerializer,
+        "FeatureProcessedEmbeddingBagCollection": FPEBCJsonSerializer,
+        "PositionWeightedModule": PWMJsonSerializer,
+        "PositionWeightedModuleCollection": PWMCJsonSerializer,
     }
 
     @classmethod