[Structured Output][Refactor] Move apply_grammar_bitmask() method from ModelRunner to structured output utils

vllm/v1/structured_output/utils.py

@@ -8,7 +8,9 @@
 import os
 from typing import TYPE_CHECKING
 
+import numpy as np
 import regex as re
+import torch
 from cachetools import LRUCache
 from diskcache import Cache
 
@@ -20,9 +22,13 @@
     import outlines_core as oc
     import transformers.file_utils as file_utils
     import transformers.models.gpt2.tokenization_gpt2 as tokenization_gpt2
+    import xgrammar as xgr
 
     from vllm.transformers_utils.tokenizer import AnyTokenizer
+    from vllm.v1.core.sched.output import SchedulerOutput
+    from vllm.v1.worker.gpu_input_batch import InputBatch
 else:
+    xgr = LazyLoader("xgr", globals(), "xgrammar")
     oc = LazyLoader("oc", globals(), "outlines_core")
     file_utils = LazyLoader("file_utils", globals(), "transformers.file_utils")
     tokenization_gpt2 = LazyLoader(
@@ -36,6 +42,80 @@
 CACHE = None
 
 
+def apply_grammar_bitmask(
+    scheduler_output: SchedulerOutput,
+    input_batch: InputBatch,
+    logits: torch.Tensor,
+    device: torch.device,
+) -> None:
+    """
+    Apply grammar bitmask to output logits of the model with xgrammar function.
+
+    Args:
+        scheduler_output (SchedulerOutput): The result of engine scheduling.
+        input_batch (InputBatch): The input of model runner.
+        logits (torch.Tensor): The output logits of model forward.
+        device (torch.device): The device that model runner running on.
+    """
+    grammar_bitmask = scheduler_output.grammar_bitmask
+    if grammar_bitmask is None:
+        return
+
+    # We receive the structured output bitmask from the scheduler,
+    # compacted to contain bitmasks only for structured output requests.
+    # The order of the requests in the bitmask is not guaranteed to be the
+    # same as the order of the requests in the gpu runner's batch. We need
+    # to sort the bitmask to match the order of the requests used here.
+
+    # Get the batch indices of the structured output requests.
+    # Keep track of the number of speculative tokens scheduled for every
+    # request in the batch, as the logit indices are offset by this amount.
+    struct_out_req_batch_indices: dict[str, int] = {}
+    cumulative_offset = 0
+    seq = sorted(input_batch.req_id_to_index.items(), key=lambda x: x[1])
+    for req_id, batch_index in seq:
+        logit_index = batch_index + cumulative_offset
+        cumulative_offset += len(
+            scheduler_output.scheduled_spec_decode_tokens.get(req_id, []))
+        if req_id in scheduler_output.structured_output_request_ids:
+            struct_out_req_batch_indices[req_id] = logit_index
+
+    out_indices = []
+
+    # Reorder the bitmask to match the order of the requests in the batch.
+    sorted_bitmask = np.full(shape=(logits.shape[0], grammar_bitmask.shape[1]),
+                             fill_value=-1,
+                             dtype=grammar_bitmask.dtype)
+    cumulative_index = 0
+    seq = sorted(scheduler_output.structured_output_request_ids.items(),
+                 key=lambda x: x[1])
+    for req_id, _ in seq:
+        logit_index = struct_out_req_batch_indices[req_id]
+        num_spec_tokens = len(
+            scheduler_output.scheduled_spec_decode_tokens.get(req_id, []))
+        for i in range(1 + num_spec_tokens):
+            sorted_bitmask[logit_index + i] = \
+                grammar_bitmask[cumulative_index + i]
+            out_indices.append(logit_index + i)
+        cumulative_index += 1 + num_spec_tokens
+    grammar_bitmask = sorted_bitmask
+
+    # If the length of out indices and the logits have the same shape
+    # we don't need to pass indices to the kernel,
+    # since the bitmask is already aligned with the logits.
+    skip_out_indices = len(out_indices) == logits.shape[0]
+
+    # Serialization of np.ndarray is much more efficient than a tensor,
+    # so we receive it in that format.
+    grammar_bitmask = torch.from_numpy(grammar_bitmask).contiguous()
+
+    xgr.apply_token_bitmask_inplace(
+        logits,
+        grammar_bitmask.to(device, non_blocking=True),
+        indices=out_indices if not skip_out_indices else None,
+    )
+
+
 class OutlinesVocabulary:
     """
     Wrapper class for `outlines_core.Vocabulary`,

vllm/v1/worker/gpu_model_runner.py

@@ -53,7 +53,7 @@
 from vllm.sequence import IntermediateTensors, PoolerOutput
 from vllm.tasks import GenerationTask, PoolingTask, SupportedTask
 from vllm.utils import (STR_DTYPE_TO_TORCH_DTYPE, DeviceMemoryProfiler,
-                        GiB_bytes, LazyLoader, check_use_alibi, get_dtype_size,
+                        GiB_bytes, check_use_alibi, get_dtype_size,
                         is_pin_memory_available, round_up, supports_dynamo)
 from vllm.v1.attention.backends.gdn_attn import GDNAttentionMetadataBuilder
 from vllm.v1.attention.backends.utils import (
@@ -83,6 +83,7 @@
 from vllm.v1.spec_decode.medusa import MedusaProposer
 from vllm.v1.spec_decode.metadata import SpecDecodeMetadata
 from vllm.v1.spec_decode.ngram_proposer import NgramProposer
+from vllm.v1.structured_output.utils import apply_grammar_bitmask
 from vllm.v1.utils import CpuGpuBuffer, record_function_or_nullcontext
 from vllm.v1.worker.gpu_input_batch import CachedRequestState, InputBatch
 from vllm.v1.worker.kv_connector_model_runner_mixin import (
@@ -95,12 +96,8 @@
                     scatter_mm_placeholders)
 
 if TYPE_CHECKING:
-    import xgrammar as xgr
-
     from vllm.model_executor.model_loader.tensorizer import TensorizerConfig
     from vllm.v1.core.sched.output import SchedulerOutput
-else:
-    xgr = LazyLoader("xgr", globals(), "xgrammar")
 
 logger = init_logger(__name__)
 
@@ -1561,71 +1558,6 @@ def get_supported_tasks(self) -> tuple[SupportedTask, ...]:
 
         return tuple(tasks)
 
-    def apply_grammar_bitmask(
-        self,
-        scheduler_output: "SchedulerOutput",
-        logits: torch.Tensor,
-    ):
-        grammar_bitmask = scheduler_output.grammar_bitmask
-        if grammar_bitmask is None:
-            return
-
-        # We receive the structured output bitmask from the scheduler,
-        # compacted to contain bitmasks only for structured output requests.
-        # The order of the requests in the bitmask is not guaranteed to be the
-        # same as the order of the requests in the gpu runner's batch. We need
-        # to sort the bitmask to match the order of the requests used here.
-
-        # Get the batch indices of the structured output requests.
-        # Keep track of the number of speculative tokens scheduled for every
-        # request in the batch, as the logit indices are offset by this amount.
-        struct_out_req_batch_indices: dict[str, int] = {}
-        cumulative_offset = 0
-        seq = sorted(self.input_batch.req_id_to_index.items(),
-                     key=lambda x: x[1])
-        for req_id, batch_index in seq:
-            logit_index = batch_index + cumulative_offset
-            cumulative_offset += len(
-                scheduler_output.scheduled_spec_decode_tokens.get(req_id, []))
-            if req_id in scheduler_output.structured_output_request_ids:
-                struct_out_req_batch_indices[req_id] = logit_index
-
-        out_indices = []
-
-        # Reorder the bitmask to match the order of the requests in the batch.
-        sorted_bitmask = np.full(shape=(logits.shape[0],
-                                        grammar_bitmask.shape[1]),
-                                 fill_value=-1,
-                                 dtype=grammar_bitmask.dtype)
-        cumulative_index = 0
-        seq = sorted(scheduler_output.structured_output_request_ids.items(),
-                     key=lambda x: x[1])
-        for req_id, _ in seq:
-            logit_index = struct_out_req_batch_indices[req_id]
-            num_spec_tokens = len(
-                scheduler_output.scheduled_spec_decode_tokens.get(req_id, []))
-            for i in range(1 + num_spec_tokens):
-                sorted_bitmask[logit_index + i] = \
-                    grammar_bitmask[cumulative_index + i]
-                out_indices.append(logit_index + i)
-            cumulative_index += 1 + num_spec_tokens
-        grammar_bitmask = sorted_bitmask
-
-        # If the length of out indices and the logits have the same shape
-        # we don't need to pass indices to the kernel,
-        # since the bitmask is already aligned with the logits.
-        skip_out_indices = len(out_indices) == logits.shape[0]
-
-        # Serialization of np.ndarray is much more efficient than a tensor,
-        # so we receive it in that format.
-        grammar_bitmask = torch.from_numpy(grammar_bitmask).contiguous()
-
-        xgr.apply_token_bitmask_inplace(
-            logits,
-            grammar_bitmask.to(self.device, non_blocking=True),
-            indices=out_indices if not skip_out_indices else None,
-        )
-
     def sync_and_slice_intermediate_tensors(
             self, num_tokens: int, intermediate_tensors: IntermediateTensors,
             sync_self: bool) -> IntermediateTensors:
@@ -2128,7 +2060,8 @@ def execute_model(
 
             # Apply structured output bitmasks if present
             if scheduler_output.grammar_bitmask is not None:
-                self.apply_grammar_bitmask(scheduler_output, logits)
+                apply_grammar_bitmask(scheduler_output, self.input_batch,
+                                      logits, self.device)
 
         with record_function_or_nullcontext("Sample"):
             sampler_output = self._sample(logits, spec_decode_metadata)