[Bugfix][Rocm] Fix shared expert weight loading failure in DeepSeek-MTP (#27563)

Signed-off-by: zhyajie <yajizhan@amd.com>
Co-authored-by: zhyajie <yajizhan@amd.com>

vllm/model_executor/models/deepseek_mtp.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-from collections.abc import Iterable
+import typing
+from collections.abc import Callable, Iterable
 
 import torch
 import torch.nn as nn
 from transformers import PretrainedConfig
 
+from vllm._aiter_ops import rocm_aiter_ops
 from vllm.compilation.decorators import support_torch_compile
 from vllm.config import VllmConfig
 from vllm.logger import init_logger
-from vllm.model_executor.layers.fused_moe import FusedMoE
+from vllm.model_executor.layers.fused_moe import SharedFusedMoE
 from vllm.model_executor.layers.layernorm import RMSNorm
 from vllm.model_executor.layers.logits_processor import LogitsProcessor
 from vllm.model_executor.layers.quantization import QuantizationConfig
@@ -231,6 +233,9 @@ class DeepSeekMTP(nn.Module, SupportsPP, DeepseekV2MixtureOfExperts):
         return self.model.compute_logits(hidden_states, spec_step_idx)
 
     def load_weights(self, weights: Iterable[tuple[str, torch.Tensor]]) -> set[str]:
+        rocm_aiter_moe_shared_expert_enabled = (
+            rocm_aiter_ops.is_fusion_moe_shared_experts_enabled()
+        )
         stacked_params_mapping = [
             ("gate_up_proj", "gate_proj", 0),
             ("gate_up_proj", "up_proj", 1),
@@ -238,11 +243,16 @@ class DeepSeekMTP(nn.Module, SupportsPP, DeepseekV2MixtureOfExperts):
             ("fused_qkv_a_proj", "kv_a_proj_with_mqa", 1),
         ]
 
-        expert_params_mapping = FusedMoE.make_expert_params_mapping(
+        expert_params_mapping = SharedFusedMoE.make_expert_params_mapping(
             ckpt_gate_proj_name="gate_proj",
             ckpt_down_proj_name="down_proj",
             ckpt_up_proj_name="up_proj",
-            num_experts=self.config.n_routed_experts,
+            num_experts=self.config.n_routed_experts
+            + (
+                self.config.n_shared_experts
+                if rocm_aiter_moe_shared_expert_enabled
+                else 0
+            ),
         )
 
         params_dict = dict(self.named_parameters())
@@ -253,6 +263,9 @@ class DeepSeekMTP(nn.Module, SupportsPP, DeepseekV2MixtureOfExperts):
             spec_layer = get_spec_layer_idx_from_weight_name(self.config, name)
             if spec_layer is None:
                 continue
+            is_fusion_moe_shared_experts_layer = (
+                rocm_aiter_moe_shared_expert_enabled and ("mlp.shared_experts" in name)
+            )
             name = self._rewrite_spec_layer_name(spec_layer, name)
             for param_name, weight_name, shard_id in stacked_params_mapping:
                 # Skip non-stacked layers and experts (experts handled below).
@@ -266,6 +279,8 @@ class DeepSeekMTP(nn.Module, SupportsPP, DeepseekV2MixtureOfExperts):
                 # for mlp.experts[0].gate_gate_up_proj, which breaks load.
                 if ("mlp.experts." in name) and name not in params_dict:
                     continue
+                if is_fusion_moe_shared_experts_layer:
+                    continue
                 name_mapped = name.replace(weight_name, param_name)
 
                 # QKV fusion is optional, fall back to normal
@@ -286,45 +301,105 @@ class DeepSeekMTP(nn.Module, SupportsPP, DeepseekV2MixtureOfExperts):
                 weight_loader(param, loaded_weight, shard_id)
                 break
             else:
-                for mapping in expert_params_mapping:
-                    param_name, weight_name, expert_id, shard_id = mapping
-                    if weight_name not in name:
-                        continue
-                    name = name.replace(weight_name, param_name)
-
-                    param = params_dict[name]
-                    weight_loader = param.weight_loader
-                    weight_loader(
-                        param,
-                        loaded_weight,
-                        name,
-                        shard_id=shard_id,
-                        expert_id=expert_id,
-                    )
-                    break
-                else:
-                    # Skip loading extra bias for GPTQ models.
-                    if name.endswith(".bias") and name not in params_dict:
-                        continue
-
-                    name = maybe_remap_kv_scale_name(name, params_dict)
-                    if name is None:
-                        continue
-
-                    # According to DeepSeek-V3 Technical Report, MTP modules
-                    # shares embedding layer. We only load the first weights.
-                    if (
-                        spec_layer != self.model.mtp_start_layer_idx
-                        and ".layers" not in name
-                    ):
-                        continue
-
-                    param = params_dict[name]
-                    weight_loader = getattr(
-                        param, "weight_loader", default_weight_loader
+                # Special handling: when AITER fusion_shared_experts is enabled,
+                # checkpoints may provide a single widened shared_experts tensor
+                # without explicit expert indices
+                # (e.g. ...mlp.shared_experts.gate_proj.weight).
+                # For models with multiple shared experts, split that tensor
+                # evenly into per-shared-expert slices and load them into
+                # appended expert slots mlp.experts.{n_routed_experts + j}.*
+                # accordingly.
+                num_chunks = 1
+                if is_fusion_moe_shared_experts_layer:
+                    num_chunks = getattr(self.config, "n_shared_experts", 1) or 1
+                    # Determine split axis based on op type
+                    # gate/up: ColumnParallel → split along dim 0
+                    # down: RowParallel → split along dim 1
+                    split_dim = 1 if "down_proj.weight" in name else 0
+                    total = loaded_weight.shape[split_dim]
+                    assert total % num_chunks == 0, (
+                        f"Shared expert weight dim {total} "
+                        f"not divisible by num_chunks {num_chunks}"
                     )
-                    weight_loader(param, loaded_weight)
-            loaded_params.add(name)
+                    chunk_size = total // num_chunks
+
+                for j in range(num_chunks):
+                    chunk_name = name
+                    weight_to_load = loaded_weight
+
+                    if is_fusion_moe_shared_experts_layer:
+                        if split_dim == 0:
+                            weight_to_load = loaded_weight[
+                                j * chunk_size : (j + 1) * chunk_size, :
+                            ]
+                        else:
+                            weight_to_load = loaded_weight[
+                                :, j * chunk_size : (j + 1) * chunk_size
+                            ]
+                        # Synthesize an expert-style name so expert mapping
+                        # can route it
+                        chunk_name = name.replace(
+                            "mlp.shared_experts",
+                            f"mlp.experts.{self.config.n_routed_experts + j}",
+                        )
+
+                    # Use expert_params_mapping to locate the destination
+                    # param and delegate to its expert-aware weight_loader
+                    # with expert_id.
+                    for mapping in expert_params_mapping:
+                        param_name, weight_name, expert_id, shard_id = mapping
+                        if weight_name not in chunk_name:
+                            continue
+
+                        # Do not modify `name` since the loop may continue here
+                        # Instead, create a new variable
+                        name_mapped = chunk_name.replace(weight_name, param_name)
+
+                        param = params_dict[name_mapped]
+                        # We should ask the weight loader to return success or
+                        # not here since otherwise we may skip experts with
+                        # other available replicas.
+                        weight_loader = typing.cast(
+                            Callable[..., bool], param.weight_loader
+                        )
+                        success = weight_loader(
+                            param,
+                            weight_to_load,
+                            name_mapped,
+                            shard_id=shard_id,
+                            expert_id=expert_id,
+                            return_success=True,
+                        )
+                        if success:
+                            if not is_fusion_moe_shared_experts_layer:
+                                name = name_mapped
+                            else:
+                                loaded_params.add(name_mapped)
+                            break
+                    else:
+                        # Skip loading extra bias for GPTQ models.
+                        if name.endswith(".bias") and name not in params_dict:
+                            continue
+
+                        name = maybe_remap_kv_scale_name(name, params_dict)
+                        if name is None:
+                            continue
+
+                        # According to DeepSeek-V3 Technical Report, MTP modules
+                        # shares embedding layer. We only load the first weights.
+                        if (
+                            spec_layer != self.model.mtp_start_layer_idx
+                            and ".layers" not in name
+                        ):
+                            continue
+
+                        param = params_dict[name]
+                        weight_loader = getattr(
+                            param, "weight_loader", default_weight_loader
+                        )
+                        weight_loader(param, loaded_weight)
+            if not is_fusion_moe_shared_experts_layer:
+                loaded_params.add(name)
         return loaded_params
 
     def _rewrite_spec_layer_name(self, spec_layer: int, name: str) -> str:

vllm/model_executor/models/deepseek_v2.py

@@ -1479,8 +1479,8 @@ class DeepseekV2ForCausalLM(
             if spec_layer is not None:
                 continue  # skip spec decode layers for main model
 
-            is_fuse_shared_experts_layer = rocm_aiter_moe_shared_expert_enabled and (
-                "mlp.shared_experts" in name
+            is_fusion_moe_shared_experts_layer = (
+                rocm_aiter_moe_shared_expert_enabled and ("mlp.shared_experts" in name)
             )
 
             for param_name, weight_name, shard_id in stacked_params_mapping:
@@ -1495,7 +1495,7 @@ class DeepseekV2ForCausalLM(
                 # for mlp.experts[0].gate_gate_up_proj, which breaks load.
                 if ("mlp.experts." in name) and name not in params_dict:
                     continue
-                if is_fuse_shared_experts_layer:
+                if is_fusion_moe_shared_experts_layer:
                     continue
                 name_mapped = name.replace(weight_name, param_name)
 
@@ -1531,7 +1531,7 @@ class DeepseekV2ForCausalLM(
                 # appended expert slots mlp.experts.{n_routed_experts + j}.*
                 # accordingly.
                 num_chunks = 1
-                if is_fuse_shared_experts_layer:
+                if is_fusion_moe_shared_experts_layer:
                     num_chunks = getattr(self.config, "n_shared_experts", 1) or 1
                     # Determine split axis based on op type
                     # gate/up: ColumnParallel → split along dim 0
@@ -1548,7 +1548,7 @@ class DeepseekV2ForCausalLM(
                     chunk_name = name
                     weight_to_load = loaded_weight
 
-                    if is_fuse_shared_experts_layer:
+                    if is_fusion_moe_shared_experts_layer:
                         if split_dim == 0:
                             weight_to_load = loaded_weight[
                                 j * chunk_size : (j + 1) * chunk_size, :
@@ -1599,7 +1599,7 @@ class DeepseekV2ForCausalLM(
                             return_success=True,
                         )
                         if success:
-                            if not is_fuse_shared_experts_layer:
+                            if not is_fusion_moe_shared_experts_layer:
                                 name = name_mapped
                             else:
                                 loaded_params.add(name_mapped)
@@ -1628,7 +1628,7 @@ class DeepseekV2ForCausalLM(
                             param, "weight_loader", default_weight_loader
                         )
                         weight_loader(param, loaded_weight)
-            if not is_fuse_shared_experts_layer:
+            if not is_fusion_moe_shared_experts_layer:
                 loaded_params.add(name)
 
         return loaded_params