Change the type signature of MixtureOfExperts.expert_weights to MutableSequence[Sequence[Tensor]] (#33573)

Signed-off-by: Sage Moore <sagmoore@redhat.com>
Co-authored-by: Robert Shaw <114415538+robertgshaw2-redhat@users.noreply.github.com>

vllm/distributed/eplb/rebalance_execute.py

@@ -6,7 +6,7 @@ The actual execution of the rearrangement.
 This involves the exchange of expert weights between GPUs.
 """
 
-from collections.abc import Iterable, Sequence
+from collections.abc import Sequence
 from dataclasses import dataclass
 
 import numpy as np
@@ -153,7 +153,7 @@ def move_to_buffer(
     num_local_experts: int,
     old_indices: np.ndarray,
     new_indices: np.ndarray,
-    expert_weights: Iterable[torch.Tensor],
+    expert_weights: Sequence[torch.Tensor],
     expert_weights_buffers: Sequence[torch.Tensor],
     cuda_stream: torch.cuda.Stream | None,
     ep_group: ProcessGroup,
@@ -355,7 +355,7 @@ def move_to_buffer(
 
 
 def move_from_buffer(
-    expert_weights: Iterable[torch.Tensor],
+    expert_weights: Sequence[torch.Tensor],
     expert_weights_buffers: list[torch.Tensor],
     is_unchanged: np.ndarray,
     is_received_locally: np.ndarray,
@@ -436,7 +436,7 @@ def move_from_buffer(
 async def transfer_layer(
     old_global_expert_indices: torch.Tensor,
     new_global_expert_indices: torch.Tensor,
-    expert_weights: Sequence[Iterable[torch.Tensor]],
+    expert_weights: Sequence[Sequence[torch.Tensor]],
     expert_weights_buffer: Sequence[torch.Tensor],
     ep_group: ProcessGroup,
     is_profile: bool = False,
@@ -488,7 +488,8 @@ async def transfer_layer(
     assert old_global_expert_indices.shape[1] == new_global_expert_indices.shape[1]
     num_moe_layers, num_physical_experts = old_global_expert_indices.shape
     assert len(expert_weights) == num_moe_layers
-    num_local_physical_experts = next(iter(expert_weights[0])).shape[0]
+    assert len(expert_weights[0]) >= 1
+    num_local_physical_experts = expert_weights[0][0].shape[0]
     assert new_global_expert_indices.shape == (num_moe_layers, num_physical_experts)
     assert num_physical_experts == ep_size * num_local_physical_experts
 
@@ -510,7 +511,7 @@ async def transfer_layer(
 def rearrange_expert_weights_inplace(
     old_global_expert_indices: torch.Tensor,
     new_global_expert_indices: torch.Tensor,
-    expert_weights: Sequence[Iterable[torch.Tensor]],
+    expert_weights: Sequence[Sequence[torch.Tensor]],
     ep_group: ProcessGroup,
     is_profile: bool = False,
     rank_mapping: dict[int, int] | None = None,
@@ -553,8 +554,9 @@ def rearrange_expert_weights_inplace(
 
     num_moe_layers, num_physical_experts = old_global_expert_indices.shape
     assert len(expert_weights) == num_moe_layers
+    assert len(expert_weights[0]) >= 1
 
-    num_local_physical_experts = next(iter(expert_weights[0])).shape[0]
+    num_local_physical_experts = expert_weights[0][0].shape[0]
     assert new_global_expert_indices.shape == (num_moe_layers, num_physical_experts)
 
     ep_size = ep_group.size()

vllm/model_executor/models/interfaces.py

@@ -2,7 +2,14 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 import asyncio
-from collections.abc import AsyncGenerator, Callable, Iterable, Mapping, MutableSequence
+from collections.abc import (
+    AsyncGenerator,
+    Callable,
+    Iterable,
+    Mapping,
+    MutableSequence,
+    Sequence,
+)
 from contextlib import ExitStack, contextmanager, nullcontext
 from typing import (
     TYPE_CHECKING,
@@ -818,7 +825,7 @@ class MixtureOfExperts(Protocol):
     Check if the model is a mixture of experts (MoE) model.
     """
 
-    expert_weights: MutableSequence[Iterable[Tensor]]
+    expert_weights: MutableSequence[Sequence[Tensor]]
     """
     Expert weights saved in this rank.