[Models] Improve iteration over layers (#19497)

Signed-off-by: Lukas Geiger <lukas.geiger94@gmail.com>

vllm/model_executor/models/qwen3_moe.py

@@ -24,6 +24,7 @@
 """Inference-only Qwen3MoE model compatible with HuggingFace weights."""
 import typing
 from collections.abc import Callable, Iterable
+from itertools import islice
 from typing import Any, Optional, Union
 
 import torch
@@ -420,8 +421,7 @@ class Qwen3MoeModel(nn.Module):
             assert intermediate_tensors is not None
             hidden_states = intermediate_tensors["hidden_states"]
             residual = intermediate_tensors["residual"]
-        for i in range(self.start_layer, self.end_layer):
-            layer = self.layers[i]
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states, residual = layer(positions, hidden_states, residual)
         if not get_pp_group().is_last_rank:
             return IntermediateTensors({

vllm/model_executor/models/seed_oss.py

@@ -23,6 +23,7 @@
 # limitations under the License.
 """Inference-only SeedOss model compatible with HuggingFace weights."""
 from collections.abc import Iterable
+from itertools import islice
 from typing import Optional, Union
 
 import torch
@@ -340,7 +341,7 @@ class SeedOssModel(nn.Module):
             assert intermediate_tensors is not None
             hidden_states = intermediate_tensors["hidden_states"]
             residual = intermediate_tensors["residual"]
-        for layer in self.layers[self.start_layer:self.end_layer]:
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states, residual = layer(
                 positions,
                 hidden_states,

vllm/model_executor/models/stablelm.py

@@ -22,6 +22,7 @@
 """Inference-only StabeLM (https://github.com/Stability-AI/StableLM)
 model compatible with HuggingFace weights."""
 from collections.abc import Iterable
+from itertools import islice
 from typing import Optional, Union
 
 import torch
@@ -247,7 +248,7 @@ class StableLMEpochModel(nn.Module):
         else:
             assert intermediate_tensors is not None
             hidden_states = intermediate_tensors["hidden_states"]
-        for layer in self.layers[self.start_layer:self.end_layer]:
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states, residual = layer(positions, hidden_states)
         if not get_pp_group().is_last_rank:
             return IntermediateTensors({"hidden_states": hidden_states})

vllm/model_executor/models/starcoder2.py

@@ -21,6 +21,7 @@
 # limitations under the License.
 """ PyTorch Starcoder2 model."""
 from collections.abc import Iterable
+from itertools import islice
 from typing import Optional, Union
 
 import torch
@@ -250,7 +251,7 @@ class Starcoder2Model(nn.Module):
         else:
             assert intermediate_tensors is not None
             hidden_states = intermediate_tensors["hidden_states"]
-        for layer in self.layers[self.start_layer:self.end_layer]:
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states = layer(positions, hidden_states)
         if not get_pp_group().is_last_rank:
             return IntermediateTensors({"hidden_states": hidden_states})

vllm/model_executor/models/step3_text.py

@@ -2,6 +2,7 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 """Inference-only Jurassic model."""
 from collections.abc import Iterable
+from itertools import islice
 from typing import Any, Optional
 
 import torch
@@ -346,8 +347,7 @@ class Step3TextModel(nn.Module):
             hidden_states = intermediate_tensors["hidden_states"]
             residual = intermediate_tensors["residual"]
 
-        for i in range(self.start_layer, self.end_layer):
-            layer = self.layers[i]
+        for layer in islice(self.layers, self.start_layer, self.end_layer):
             hidden_states, residual = layer(positions, hidden_states, residual)
 
         if not get_pp_group().is_last_rank: