[shardformer] Add dropout layer in shard model and refactor policy api (

hpcaitech#3949)

* add dist dropout in model

* update docstring and bert policy with dropout

* refactor basepolicy and sharded, update bert

* update format

* update gpt2 policy

* update bert policy

* remove unused code

* update readme for new policy usage

colossalai/shardformer/README.md

@@ -55,7 +55,7 @@ colossalai run --nproc_per_node 2 --master_port 29500 test.py --config config.py
 
 ## 💡 Policy
 
-If you wanna parallel the model in a custom way, just overwrite the policy class for the Hugging Face model.
+If you wanna parallel the model in a custom way, just overwrite the policy class for the Hugging Face model. Please refer to any policy that we have pre-established, like [bert policy](./policies/bert.py) or [gpt2 policy](./policies/gpt2.py).
 
 You should do:
 
@@ -68,7 +68,7 @@ You should do:
     - Shardformer will inject the model according to this method. If you need to modify the forward or backward progress (like distributed corssentropy loss in Bert) you need to overwrite this method.
 4. Overwrite or add the param functions
     - These functions use a suffix to record the path of weight or bias for the layer.
-    - The return is a list contains some `Col_Layer` or `Row_Layer` objects, which means slice along col and row respectively.
+    - The return is a list contains some `Col_Layer`, `Row_Layer` or `Dropout_Layer` objects, which means slice along col and row respectively or as dropout layer, refer to CLASS `Layer` for more details.
 5. Overwrite `binding_policy` (Optional)
     - Overwrite to specify Shardformer will bind some weight between layers, like embedding and unembedding layers.
     - This function will return a dict, the key and value are the suffix of weight need to be binded.
@@ -123,7 +123,7 @@ class CustomPolicy(Policy):
         raise NotImplementedError
 
     @staticmethod
-    def inject_policy() -> Tuple[nn.Module, nn.Module]:
+    def inject_policy() -> Union[Tuple[nn.Module, nn.Module], None]:
         r"""
         Return the dict for the inject model
 
@@ -133,12 +133,12 @@ class CustomPolicy(Policy):
             (OrignModel, CustomModel)
             in `CustomModel`, we can overwrite the forward and backward process
         """
-        return ()
+        return None
 
     @staticmethod
-    def binding_policy() -> Dict:
+    def binding_policy() -> Union[Dict[str, str], None]:
         r"""
-        Return the dict for the binding model
+        Return the dict for the binding model, None means no need to bind
 
         Return:
             This method should return the binding relationship for some layers share the weight or bias,
@@ -148,69 +148,70 @@ class CustomPolicy(Policy):
                 "bert.embeddings.word_embeddings.weight": "cls.predictions.decoder.weight",
             }
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def attn_in() -> List:
-        """
+    def attn_in() -> Union[List, None]:
+        r"""
         Attention qkv layer
+        In this kind of method, we should return the list of ``Layer`` object, each ``Layer`` object should be
+        ``Layer`` for no slicing, ``Col_Layer`` for col slicing, ``Row_Layer`` for row slicing. And the parameters
+        in ``Layer`` object can refer to the ``Layer`` class.
 
         Returns:
             List[Layer]: List of layer object, each layer is the new
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def attn_out() -> List:
-        """
+    def attn_out() -> Union[List, None]:
+        r"""
         Attention output projection layer
 
         Returns:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def mlp_in() -> List:
-        """
+    def mlp_in() -> Union[List, None]:
+        r"""
         h -> 4h mlp layer
 
         Returns:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def mlp_out() -> List:
-        """
+    def mlp_out() -> Union[List, None]:
+        r"""
         4h -> h mlp layer
 
         Returns:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def embedding() -> List:
-        """
+    def embedding() -> Union[List, None]:
+        r"""
         Partially slice the embedding layer
-        vocab_size->vocab_size//gpu_nums
 
         Return:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def unembedding() -> List:
-        """
-        Partially slice the embedding layer
-        vocab_size->vocab_size//gpu_nums
+    def unembedding() -> Union[List, None]:
+        r"""
+        Partially slice the embedding layer, None means there is no unembedding layer
 
         Return:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
 ```
 
@@ -232,51 +233,64 @@ class CustomPolicy(Policy):
   - CLASS `Layer`:
 
     Parameters:
-    - weight (str): The weight suffix of the layer
-    - bias (str): The bias suffix of the layer
+    - suffix: (str): the suffix of the layer to indicate the attribute of the layer.
     - replace_layer (:class:`colosalai.nn`): The layer to replace the original layer
     - ignore (bool): Whether to ignore this layer if it is not in the model
+    - reversed (bool): Whether the weight in layer is reversed, commonly the weight in `torch.nn.Linear` is [out, in], but in GPT2 `Conv1D` layer is [in, out] which is reversed.
+    - n_cast (int): The number of weight will cast to, like q, k, v in attention layer, n_cast should be 3. commonly in TP, we just chunk the weight with the number of devices, but in multi-head attention, we need to chunk the weight with the number of $ devices * n\_head $, and each device should have a part of Q, K and V weight.
 
-    This class is used to specify the replacement policy for a particular layer. If `replace_layer` is None, only parameter partitioning will be performed without replacing the layer class.
+    This class is a base class used to specify the replacement policy and the suffix the layer for a particular layer.
 
     CLASS `Col_Layer(Layer)`:
+      - weight (str): The weight suffix of the layer
+      - bias (str): The bias suffix of the layer
       - gather_output (bool): Whether the output of this layer can be gathered, like the last layer can be gathered, but most of the time, the intermediate layers of the model do not need to be gathered.
 
-      This class inherited from `Layer`, representing the layer will be sliced along column.
+      This class inherited from `Layer`, representing the layer will be sliced along colum and indicate the attributes of weight and bias. Setting `bias` to `None` means ignoring bias, regardless of whether or not it originally exists.
 
     CLASS `Row_Layer(Layer)`:
+      - weight (str): The weight suffix of the layer
+      - bias (str): The bias suffix of the layer
 
-      This class inherited from `Layer`, representing the layer will be sliced along row.
+      This class inherited from `Layer`, representing the layer will be sliced along row. Just like `Col_Layer` but in tensor parrallel, there is no need to gather the output of layer sliced by row.
 
   - CLASS `Policy`:
 
     In Shardformer, this class holds significant importance as it defines the model partitioning methods, required parameter modifications, and model injection techniques all within a single Policy class.
     - `Policy.attn_in()/attn_out()/mlp_in()/mlp_out()/embedding()/unembedding()`......
 
       These functions define the partitioning methods of the parameters at different locations in the model. Each function returns a list of objects of Layer class that specify the replacement approach for these parameters. Shardformer also supports user-defined functions for modifying their models, in addition to the listed functions.
+
     - `Policy.argument_policy()`
 
       In this function, the user should use multiple dict to define which class of layers will require replacement. This includes the attributes and parameters that need to be modified or replaced. Attributes are stored in the form of a "suffix-string: value" dict, while parameters are stored via multiple static methods that return the replacement approach.
+
     - `Policy.inject_policy()`
 
       This function will return the injected model to replace the original model. The new model should be a nn.Module class which includes modified forward or backward functions or anything else.
+
     - `Policy.binding_policy()`
 
       This function will return the weight sharing information in the model in some dict. The key and value are both the suffixes of the shared parameters.
 
+
   - CLASS `ModelSharder(model, policy)`:
 
     This class helps shard the model, the parameter is the created transformers model and the custom policy. If custom policy is None, shardformer will automatically get already defined policy for the model.
+
     - `ModelShard.inject_model()`
 
       This function is used to inject the model to modify the forward and backward progress.
+
     - `ModelShard.replace_layer()`
 
       This function is used to replace the original layers with colossalai layer to make them paralleled and can do distributed communication.
+
     - `ModelShard.bind_layer()`
 
       This function is used to help different layers share weight or bias.
 
+
   - CLASS `Slicer`:
 
     This class is used to slice tensor according to policy.

colossalai/shardformer/policies/basepolicy.py

@@ -1,7 +1,7 @@
 # part of code modified from https://github.com/tunib-ai/parallelformers
 
 from dataclasses import dataclass
-from typing import Any, Callable, Dict, List, Tuple, Type
+from typing import Any, Callable, Dict, List, Tuple, Union
 
 import torch.nn as nn
 
@@ -25,8 +25,7 @@ class Layer:
     The layer object for the policy
 
     Args:
-        weight (str): The weight suffix of the layer
-        bias (str): The bias suffix of the layer
+        suffix: (str): the suffix of the layer.
         replace_layer (:class:`colosalai.nn`): The layer to replace the original layer
         ignore (bool): Whether to ignore this layer if it is not in the model
         reversed (bool): Whether the weight in layer is reversed, commonly the weight in `torch.nn.Linear` is [out, in],
@@ -35,8 +34,7 @@ class Layer:
                         but in multi-head attention, we need to chunk the weight with the number of devices * n_head, and
                         each device should have a part of Q, K and V weight.
     """
-    weight: str = None
-    bias: str = None
+    suffix: str = None
     replace_layer: Any = None
     ignore: bool = False
     reversed: bool = False
@@ -46,20 +44,40 @@ class Layer:
 @dataclass
 class Col_Layer(Layer):
     r"""
-    Class for col shard layer in MegatronLM
+    Class for col shard layer in tensor parrallel
 
     Args:
+        weight (str): The weight suffix of the layer
+        bias (str): The bias suffix of the layer
         gather_output (bool): Whether to gather the output of the layer
     """
+    weight: str = None
+    bias: str = None
     gather_output: bool = False
 
 
 @dataclass
 class Row_Layer(Layer):
     r"""
-    Class for col shard layer in MegatronLM
+    Class for col shard layer in tensor parrallel
+
+    Args:
+        weight (str): The weight suffix of the layer
+        bias (str): The bias suffix of the layer
     """
-    pass
+    weight: str = None
+    bias: str = None
+
+
+@dataclass
+class Dropout_Layer(Layer):
+    r"""
+    Class for dropout layer in tensor parrallel
+
+    Args:
+        p (str): The dropout rate suffix of the layer
+    """
+    p: str = None
 
 
 class Policy():
@@ -82,14 +100,14 @@ class for the example.
     """
 
     @staticmethod
-    def argument_policy(model_config, shard_config: int) -> Dict[nn.Module, Argument]:
+    def argument_policy(model_config, world_size: int) -> Dict[nn.Module, Argument]:
         r"""
         Return the dict for the modify policy, the key is the original layer class and the value is the
         argument for the modify layer
 
         Args:
             model_config (:class:`tansformer.Config`): The config of transformer model
-            shard_config (:class:`ShardConfig`): The config for sharding model
+            world_size (int)): The world size of sharding model
 
         Return:
             Dict for the modify policy,
@@ -126,7 +144,7 @@ def argument_policy(model_config, shard_config: int) -> Dict[nn.Module, Argument
         raise NotImplementedError
 
     @staticmethod
-    def inject_policy() -> Tuple[nn.Module, nn.Module]:
+    def inject_policy() -> Union[Tuple[nn.Module, nn.Module], None]:
         r"""
         Return the dict for the inject model
 
@@ -139,9 +157,9 @@ def inject_policy() -> Tuple[nn.Module, nn.Module]:
         return None
 
     @staticmethod
-    def binding_policy() -> Dict:
+    def binding_policy() -> Union[Dict[str, str], None]:
         r"""
-        Return the dict for the binding model
+        Return the dict for the binding model, None means no need to bind
 
         Return:
             This method should return the binding relationship for some layers share the weight or bias,
@@ -154,7 +172,7 @@ def binding_policy() -> Dict:
         return None
 
     @staticmethod
-    def attn_in() -> List:
+    def attn_in() -> Union[List, None]:
         r"""
         Attention qkv layer
         In this kind of method, we should return the list of ``Layer`` object, each ``Layer`` object should be
@@ -164,52 +182,52 @@ def attn_in() -> List:
         Returns:
             List[Layer]: List of layer object, each layer is the new
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def attn_out() -> List:
+    def attn_out() -> Union[List, None]:
         r"""
         Attention output projection layer
 
         Returns:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def mlp_in() -> List:
+    def mlp_in() -> Union[List, None]:
         r"""
         h -> 4h mlp layer
 
         Returns:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def mlp_out() -> List:
+    def mlp_out() -> Union[List, None]:
         r"""
         4h -> h mlp layer
 
         Returns:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def embedding() -> List:
+    def embedding() -> Union[List, None]:
         r"""
         Partially slice the embedding layer
 
         Return:
             List[Layer]: List of layer object
         """
-        return NotImplementedError
+        return None
 
     @staticmethod
-    def unembedding() -> List:
+    def unembedding() -> Union[List, None]:
         r"""
-        Partially slice the embedding layer
+        Partially slice the embedding layer, None means there is no unembedding layer
 
         Return:
             List[Layer]: List of layer object