[Bugfix] EAGLE output norm bug (#14464)

Signed-off-by: Bryan Lu <yuzhelu@amazon.com>

docs/source/features/spec_decode.md

@@ -162,7 +162,7 @@ A variety of speculative models of this type are available on HF hub:
 ## Speculating using EAGLE based draft models
 
 The following code configures vLLM to use speculative decoding where proposals are generated by
-an [EAGLE (Extrapolation Algorithm for Greater Language-model Efficiency)](https://arxiv.org/pdf/2401.15077) based draft model.
+an [EAGLE (Extrapolation Algorithm for Greater Language-model Efficiency)](https://arxiv.org/pdf/2401.15077) based draft model. A more detailed example for offline mode, including how to extract request level acceptance rate, can be found [here](<gh-file:examples/offline_inference/eagle.py>).
 
 ```python
 from vllm import LLM, SamplingParams

examples/offline_inference/eagle.py

@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: Apache-2.0
+import argparse
+import json
+import os
+
+from transformers import AutoTokenizer
+
+from vllm import LLM, SamplingParams
+
+parser = argparse.ArgumentParser()
+
+parser.add_argument(
+    "--dataset",
+    type=str,
+    default="./examples/data/gsm8k.jsonl",
+    help="downloaded from the eagle repo " \
+    "https://github.com/SafeAILab/EAGLE/blob/main/eagle/data/"
+)
+parser.add_argument("--max_num_seqs", type=int, default=8)
+parser.add_argument("--num_prompts", type=int, default=80)
+parser.add_argument("--num_spec_tokens", type=int, default=2)
+parser.add_argument("--tp", type=int, default=1)
+parser.add_argument("--draft_tp", type=int, default=1)
+parser.add_argument("--enforce_eager", action='store_true')
+parser.add_argument("--enable_chunked_prefill", action='store_true')
+parser.add_argument("--max_num_batched_tokens", type=int, default=2048)
+parser.add_argument("--temp", type=float, default=0)
+
+args = parser.parse_args()
+
+print(args)
+
+model_dir = "meta-llama/Meta-Llama-3-8B-Instruct"
+eagle_dir = "abhigoyal/EAGLE-LLaMA3-Instruct-8B-vllm"
+
+max_model_len = 2048
+
+tokenizer = AutoTokenizer.from_pretrained(model_dir)
+
+if os.path.exists(args.dataset):
+    prompts = []
+    num_prompts = args.num_prompts
+    with open(args.dataset) as f:
+        for line in f:
+            data = json.loads(line)
+            prompts.append(data["turns"][0])
+else:
+    prompts = ["The future of AI is", "The president of the United States is"]
+
+prompts = prompts[:args.num_prompts]
+num_prompts = len(prompts)
+
+prompt_ids = [
+    tokenizer.apply_chat_template([{
+        "role": "user",
+        "content": prompt
+    }],
+                                  add_generation_prompt=True)
+    for prompt in prompts
+]
+
+llm = LLM(
+    model=model_dir,
+    trust_remote_code=True,
+    tensor_parallel_size=args.tp,
+    enable_chunked_prefill=args.enable_chunked_prefill,
+    max_num_batched_tokens=args.max_num_batched_tokens,
+    enforce_eager=args.enforce_eager,
+    max_model_len=max_model_len,
+    max_num_seqs=args.max_num_seqs,
+    gpu_memory_utilization=0.8,
+    speculative_model=eagle_dir,
+    num_speculative_tokens=args.num_spec_tokens,
+    speculative_draft_tensor_parallel_size=args.draft_tp,
+    speculative_max_model_len=max_model_len,
+    disable_log_stats=False,
+)
+
+sampling_params = SamplingParams(temperature=args.temp, max_tokens=256)
+
+outputs = llm.generate(prompt_token_ids=prompt_ids,
+                       sampling_params=sampling_params)
+
+# calculate the average number of accepted tokens per forward pass, +1 is
+# to account for the token from the target model that's always going to be
+# accepted
+acceptance_counts = [0] * (args.num_spec_tokens + 1)
+for output in outputs:
+    for step, count in enumerate(output.metrics.spec_token_acceptance_counts):
+        acceptance_counts[step] += count
+
+print(f"mean acceptance length: \
+    {sum(acceptance_counts) / acceptance_counts[0]:.2f}")

vllm/engine/llm_engine.py

@@ -853,6 +853,10 @@ class LLMEngine:
             self.generation_config_fields, seq.eos_token_id)
 
         # Create the sequence group.
+        draft_size = 1
+        if self.vllm_config.speculative_config is not None:
+            draft_size = \
+                self.vllm_config.speculative_config.num_speculative_tokens + 1
         seq_group = SequenceGroup(
             request_id=request_id,
             seqs=[seq],
@@ -862,7 +866,8 @@ class LLMEngine:
             trace_headers=trace_headers,
             prompt_adapter_request=prompt_adapter_request,
             encoder_seq=encoder_seq,
-            priority=priority)
+            priority=priority,
+            draft_size=draft_size)
 
         return seq_group
 

vllm/engine/output_processor/multi_step.py

@@ -100,6 +100,11 @@ class MultiStepOutputProcessor(SequenceGroupOutputProcessor):
             seqs = sequence_group.get_seqs(
                 status=SequenceStatus.FINISHED_ABORTED)
 
+        for output in outputs:
+            if output.samples[0].output_token != VLLM_INVALID_TOKEN_ID:
+                sequence_group.metrics.spec_token_acceptance_counts[
+                    output.step_index] += 1
+
         assert seqs, "Expected RUNNING or FINISHED_ABORTED sequences"
         assert len(seqs) == 1, (
             "Beam search not supported in multi-step decoding.")

vllm/model_executor/models/eagle.py

@@ -38,7 +38,7 @@ class DummyOutputNorm(nn.Module):
         if residual is None:
             return x
         else:
-            return x, residual
+            return x + residual, None
 
 
 class EAGLE(nn.Module):

vllm/sequence.py

@@ -111,6 +111,13 @@ class RequestMetrics:
         model_execute_time: The time spent in the model execute function. This
                             will include model forward, block/sync across
                             workers, cpu-gpu sync time and sampling time.
+        spec_token_acceptance_counts: number of accepted speculative tokens at
+                                      each position; the first token is from 
+                                      the target model and is always accepted;
+                                      e.g., when it's [10, 8, 4, 2] for a req, 
+                                      it means there were 10 forward passes in
+                                      total, and there were 8, 4, 2 accepted 
+                                      tokens at 1st, 2nd, 3rd speculation step. 
     """
     arrival_time: float
     last_token_time: float
@@ -121,6 +128,7 @@ class RequestMetrics:
     scheduler_time: Optional[float] = None
     model_forward_time: Optional[float] = None
     model_execute_time: Optional[float] = None
+    spec_token_acceptance_counts: Optional[list[int]] = None
 
 
 class SequenceDataDelta(
@@ -639,10 +647,13 @@ class SequenceGroup:
         trace_headers: OpenTelemetry trace headers.
         prompt_adapter_request: Prompt Adapter request.
         priority: User-defined priority of the request.
+        draft_size: The number of speculative tokens plus one from the target 
+                    model; equal to max number of tokens a step can generate
+                    for single-draft speculative decoding but larger than 
+                    that for multi-draft SD (currently not supported).
     """
 
-    def __init__(
-        self,
+    def __init__(self,
                  request_id: str,
                  seqs: list[Sequence],
                  arrival_time: float,
@@ -654,7 +665,7 @@ class SequenceGroup:
                  trace_headers: Optional[Mapping[str, str]] = None,
                  prompt_adapter_request: Optional[PromptAdapterRequest] = None,
                  priority: int = 0,
-    ) -> None:
+                 draft_size: int = 1) -> None:
         self.request_id = request_id
         self.seqs = seqs
         self.first_seq = seqs[0]
@@ -667,7 +678,9 @@ class SequenceGroup:
                                       last_token_time=arrival_time,
                                       first_scheduled_time=None,
                                       first_token_time=None,
-                                      time_in_queue=None)
+                                      time_in_queue=None,
+                                      spec_token_acceptance_counts=[0] *
+                                      draft_size)
         self.last_token_latency = 0.0
         self.lora_request = lora_request
         self.prompt_logprobs: Optional[PromptLogprobs] = None
@@ -1079,6 +1092,7 @@ class CompletionSequenceGroupOutput(
     samples: list[SequenceOutput]
     # Prompt logprob for each prompt query token.
     prompt_logprobs: Optional[PromptLogprobs]
+    step_index: Optional[int] = 0
 
     def __repr__(self) -> str:
         return (f"CompletionSequenceGroupOutput(samples={self.samples}, "

vllm/spec_decode/spec_decode_worker.py

@@ -1080,7 +1080,7 @@ class SpecDecodeWorker(LoRANotSupportedWorkerBase):
                         [sequence_index][:num_logprobs],
                         topk_logprobs=topk_logprobs_by_step[step_index]
                         [sequence_index][:num_logprobs],
-                    ))
+                        step_index=step_index))
             sampler_output_list.append(
                 SamplerOutput(outputs=step_output_token_ids))
 

vllm/spec_decode/util.py

@@ -100,7 +100,7 @@ def create_sequence_group_output(
         topk_token_ids: List[Optional[int]],
         topk_logprobs: List[Optional[float]],
         prompt_logprobs: Optional[PromptLogprobs] = None,
-) -> CompletionSequenceGroupOutput:
+        step_index: Optional[int] = 0) -> CompletionSequenceGroupOutput:
     """Create a SequenceGroupOutput given the sampling results.
 
     Args:
@@ -110,6 +110,7 @@ def create_sequence_group_output(
         seq_id (int): The sequence id.
         topk_token_ids (List[Optional[int]]): The list of top-k token ids.
         topk_logprobs (List[Optional[float]]): The list of top-k logprobs.
+        step_index: (Optional[int]): The index of the speculative token.
     """
 
     logprobs = create_logprobs_output(
@@ -120,14 +121,13 @@ def create_sequence_group_output(
         topk_logprobs,
     )
 
-    return CompletionSequenceGroupOutput(
-        samples=[
+    return CompletionSequenceGroupOutput(samples=[
         SequenceOutput(parent_seq_id=seq_id,
                        output_token=token_id,
                        logprobs=logprobs)
     ],
                                          prompt_logprobs=prompt_logprobs,
-    )
+                                         step_index=step_index)
 
 
 def split_batch_by_proposal_len(