Refactor DeepSeek MoE layer to unify the two forward branches (#6325)

python/sglang/srt/models/deepseek_v2.py

@@ -194,6 +194,14 @@ class MoEGate(nn.Module):
         return logits
 
 
+def is_non_idle_and_non_empty(forward_mode, hidden_states):
+    return (
+        (forward_mode is not None)
+        and not forward_mode.is_idle()
+        and hidden_states.shape[0] > 0
+    )
+
+
 class DeepseekV2MoE(nn.Module):
 
     def __init__(
@@ -259,11 +267,12 @@ class DeepseekV2MoE(nn.Module):
                 ),
             )
 
+        self.top_k = config.num_experts_per_tok
+
         if global_server_args_dict["enable_deepep_moe"]:
             # TODO: we will support tp < ep in the future
             self.ep_size = get_tensor_model_parallel_world_size()
             self.num_experts = config.n_routed_experts
-            self.top_k = config.num_experts_per_tok
             self.renormalize = config.norm_topk_prob
             self.topk_group = config.topk_group
             self.num_expert_group = config.n_group
@@ -286,41 +295,30 @@ class DeepseekV2MoE(nn.Module):
                 return_recv_hook=True,
             )
 
+    @property
+    def _enable_deepep_moe(self):
+        return global_server_args_dict["enable_deepep_moe"]
+
     def forward(
         self, hidden_states: torch.Tensor, forward_batch: Optional[ForwardBatch] = None
     ) -> torch.Tensor:
-        if not global_server_args_dict["enable_deepep_moe"]:
-            return self.forward_normal(hidden_states)
-        else:
-            return self.forward_deepep(hidden_states, forward_batch)
-
-    def forward_normal(self, hidden_states: torch.Tensor) -> torch.Tensor:
-        shared_output = self._forward_shared_experts(hidden_states)
+        if (not self._enable_deepep_moe) or is_non_idle_and_non_empty(
+            forward_mode, hidden_states
+        ):
             # router_logits: (num_tokens, n_experts)
             router_logits = self.gate(hidden_states)
-        final_hidden_states = self.experts(
-            hidden_states=hidden_states, router_logits=router_logits
-        )
-        final_hidden_states *= self.routed_scaling_factor
-        if shared_output is not None:
-            final_hidden_states = final_hidden_states + shared_output
-        if self.tp_size > 1:
-            final_hidden_states = tensor_model_parallel_all_reduce(final_hidden_states)
-        return final_hidden_states
+        else:
+            router_logits = None
 
-    def forward_deepep(
-        self, hidden_states: torch.Tensor, forward_batch: ForwardBatch
-    ) -> torch.Tensor:
-        forward_mode = forward_batch.forward_mode
-        shared_output = None
-        if (
-            forward_mode is not None
-            and not forward_mode.is_idle()
-            and hidden_states.shape[0] > 0
+        if (self.n_share_experts_fusion == 0) and (
+            (not self._enable_deepep_moe)
+            or is_non_idle_and_non_empty(forward_mode, hidden_states)
         ):
-            # router_logits: (num_tokens, n_experts)
-            router_logits = self.gate(hidden_states)
-            shared_output = self._forward_shared_experts(hidden_states)
+            shared_output = self.shared_experts(hidden_states)
+        else:
+            shared_output = None
+
+        if self._enable_deepep_moe and (router_logits is not None):
             topk_weights, topk_idx = select_experts(
                 hidden_states=hidden_states,
                 router_logits=router_logits,
@@ -340,7 +338,8 @@ class DeepseekV2MoE(nn.Module):
             topk_weights = torch.empty(
                 (0, self.top_k), dtype=torch.float32, device=hidden_states.device
             )
-        if self.ep_size > 1:
+
+        if self._enable_deepep_moe and (self.ep_size > 1):
             # TODO(ch-wan): allow users to set num_max_dispatch_tokens_per_rank value
             (
                 hidden_states,
@@ -357,6 +356,8 @@ class DeepseekV2MoE(nn.Module):
                 topk_weights,
                 forward_mode=forward_mode,
             )
+
+        if self._enable_deepep_moe:
             final_hidden_states = self.experts(
                 hidden_states=hidden_states,
                 topk_idx=topk_idx,
@@ -368,25 +369,28 @@ class DeepseekV2MoE(nn.Module):
                 num_recv_tokens_per_expert=num_recv_tokens_per_expert,
                 forward_mode=forward_mode,
             )
-        if self.ep_size > 1:
+        else:
+            final_hidden_states = self.experts(
+                hidden_states=hidden_states, router_logits=router_logits
+            )
+
+        if self._enable_deepep_moe and (self.ep_size > 1):
             final_hidden_states = self.deepep_dispatcher.combine(
                 final_hidden_states,
                 topk_idx,
                 topk_weights,
                 forward_mode,
             )
+
         final_hidden_states *= self.routed_scaling_factor
 
         if shared_output is not None:
             final_hidden_states = final_hidden_states + shared_output
 
-        return final_hidden_states
+        if (not self._enable_deepep_moe) and (self.tp_size > 1):
+            final_hidden_states = tensor_model_parallel_all_reduce(final_hidden_states)
 
-    def _forward_shared_experts(self, hidden_states):
-        if self.n_share_experts_fusion == 0:
-            return self.shared_experts(hidden_states)
-        else:
-            return None
+        return final_hidden_states
 
 
 def yarn_get_mscale(scale: float = 1, mscale: float = 1) -> float: