Extract eh_proj Layer from ParallelLMHead for MTP to Avoid Weight Transposition Issue (#2707)

* fix mtp eh_proj layer

* fix mtp update_cfg function

* fix stringdoc

* simplify class name

Author: Deleter-D

fastdeploy/model_executor/layers/mtp_linear.py

@@ -0,0 +1,133 @@
+"""
+# Copyright (c) 2025 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+
+import paddle
+from paddle import nn
+from paddle.distributed import fleet
+
+from .utils import get_tensor
+
+
+class ParallelEHProjection(nn.Layer):
+    """
+    "Parallelized Embedding Hidden States Projection.
+    """
+
+    def __init__(
+        self,
+        fd_config,
+        num_embeddings,
+        embedding_dim,
+        prefix="",
+        with_bias=False,
+    ):
+        """
+        Parallelized Embedding Hidden States Projection.
+
+        Args:
+            fd_config (FDConfig): Arguments related to inference, containing
+                attributes such as weight_dtype, act_dtype, mp_size, hidden_size, head_dim,
+                num_attention_heads, and ffn_hidden_size.
+            num_embeddings (int): vocabulary size.
+            embedding_dim (int): size of hidden state.
+            prefix (str): full name of the layer in the state dict
+        """
+        super(ParallelEHProjection, self).__init__()
+        self.linear_weight_key = prefix + ".weight"
+        if with_bias:
+            self.linear_bias_key = prefix + ".bias"
+        else:
+            self.linear_bias_key = None
+        self.use_ep = fd_config.parallel_config.use_ep
+        self.column_cut = True
+
+        ColumnParallelLinear = fleet.meta_parallel.ColumnParallelLinear
+        RowParallelLinear = fleet.meta_parallel.RowParallelLinear
+
+        if self.use_ep:
+            self.weight = self.create_parameter(
+                shape=[embedding_dim, num_embeddings],
+                dtype=paddle.get_default_dtype(),
+                is_bias=False,
+            )
+        else:
+            if self.column_cut:
+                need_gather = True
+                self.out_linear = ColumnParallelLinear(
+                    embedding_dim,
+                    num_embeddings,
+                    mp_group=fleet.get_hybrid_communicate_group().
+                    get_model_parallel_group(),
+                    weight_attr=None,
+                    has_bias=True
+                    if self.linear_bias_key is not None else False,
+                    gather_output=need_gather,
+                    fuse_matmul_bias=False,  # False diff更小
+                )
+            else:
+                self.out_linear = RowParallelLinear(
+                    embedding_dim,
+                    num_embeddings,
+                    mp_group=fleet.get_hybrid_communicate_group().
+                    get_model_parallel_group(),
+                    weight_attr=None,
+                    has_bias=True
+                    if self.linear_bias_key is not None else False,
+                    input_is_parallel=False,
+                    fuse_matmul_bias=False,  # False diff更小
+                )
+
+    def load_state_dict(self, state_dict):
+        """
+        Load the checkpoint state dictionary into the layer.
+
+        Args:
+            state_dict (dict): A dictionary containing the checkpoint weights and biases.
+        """
+
+        if self.use_ep:
+            self.weight.set_value(
+                get_tensor(state_dict.pop(self.linear_weight_key)).astype(
+                    paddle.get_default_dtype()))
+        else:
+            weight_tensor = get_tensor(
+                state_dict.pop(self.linear_weight_key)).astype(
+                    paddle.get_default_dtype())
+            if self.out_linear.weight.shape != weight_tensor.shape:
+                weight_tensor = weight_tensor.transpose([1, 0])
+            self.out_linear.weight.set_value(weight_tensor)
+
+            if self.linear_bias_key is not None:
+                bias = get_tensor(state_dict.pop(self.linear_bias_key)).astype(
+                    paddle.get_default_dtype())
+                self.out_linear.bias.set_value(bias)
+
+    def forward(self, input):
+        """
+        Defines the forward computation of the layer.
+
+        Args:
+            input (Tensor): The input tensor to the layer.
+
+        Returns:
+            Tensor: The output tensor after processing through the layer.
+        """
+        logits = input
+        if self.use_ep:
+            logits = paddle.matmul(logits, self.weight)
+        else:
+            logits = self.out_linear(logits)
+        return logits

fastdeploy/model_executor/models/ernie4_5_mtp.py

@@ -26,7 +26,7 @@
 from paddleformers.utils.log import logger
 
 from fastdeploy.config import FDConfig, ModelConfig
-from fastdeploy.model_executor.layers.lm_head import ParallelLMHead
+from fastdeploy.model_executor.layers.mtp_linear import ParallelEHProjection
 from fastdeploy.model_executor.layers.normalization import RMSNorm
 from fastdeploy.model_executor.models.ernie4_5_moe import Ernie4_5_DecoderLayer
 from fastdeploy.model_executor.models.model_base import ModelForCasualLM
@@ -286,7 +286,7 @@ def __init__(
             prefix="ernie.mtp_hidden_norm.0",
         )
 
-        self.eh_proj = ParallelLMHead(
+        self.eh_proj = ParallelEHProjection(
             fd_config=fd_config,
             num_embeddings=fd_config.model_config.hidden_size,
             embedding_dim=fd_config.model_config.hidden_size * 2,

fastdeploy/spec_decode/mtp.py

@@ -68,8 +68,7 @@ def _update_cfg(self, main_model):
         """
         Update config for MTP from global config
         """
-        self.model_config.architectures[0] = self.model_config.architectures[
-            0].replace("MoeForCausalLM", "MTPForCausalLM")
+        self.model_config.architectures[0] = "Ernie4_5_MTPForCausalLM"
         self.speculative_config.sharing_model = main_model
         self.model_config.num_layers = 1
         self.parallel_config.model_name_or_path = (