[Model] MLPSpeculator speculative decoding support (#4947)

Signed-off-by: Thomas Parnell <tpa@zurich.ibm.com>

Co-authored-by: Thomas Parnell <tpa@zurich.ibm.com>
Co-authored-by: Nick Hill <nickhill@us.ibm.com>
Co-authored-by: Davis Wertheimer <Davis.Wertheimer@ibm.com>

examples/offline_inference_mlpspeculator.py

@@ -0,0 +1,59 @@
+import gc
+import time
+from typing import List
+
+from vllm import LLM, SamplingParams
+
+
+def time_generation(llm: LLM, prompts: List[str],
+                    sampling_params: SamplingParams):
+    # Generate texts from the prompts. The output is a list of RequestOutput
+    # objects that contain the prompt, generated text, and other information.
+    # Warmup first
+    llm.generate(prompts, sampling_params)
+    llm.generate(prompts, sampling_params)
+    start = time.time()
+    outputs = llm.generate(prompts, sampling_params)
+    end = time.time()
+    print((end - start) / sum([len(o.outputs[0].token_ids) for o in outputs]))
+    # Print the outputs.
+    for output in outputs:
+        generated_text = output.outputs[0].text
+        print(f"text: {generated_text!r}")
+
+
+if __name__ == "__main__":
+
+    template = (
+        "Below is an instruction that describes a task. Write a response "
+        "that appropriately completes the request.\n\n### Instruction:\n{}"
+        "\n\n### Response:\n")
+
+    # Sample prompts.
+    prompts = [
+        "Write about the president of the United States.",
+    ]
+    prompts = [template.format(prompt) for prompt in prompts]
+    # Create a sampling params object.
+    sampling_params = SamplingParams(temperature=0.0, max_tokens=200)
+
+    # Create an LLM without spec decoding
+    llm = LLM(model="meta-llama/Llama-2-13b-chat-hf")
+
+    print("Without speculation")
+    time_generation(llm, prompts, sampling_params)
+
+    del llm
+    gc.collect()
+
+    # Create an LLM with spec decoding
+    llm = LLM(
+        model="meta-llama/Llama-2-13b-chat-hf",
+        speculative_model="ibm-fms/llama-13b-accelerator",
+        # These are currently required for MLPSpeculator decoding
+        use_v2_block_manager=True,
+        enforce_eager=True,
+    )
+
+    print("With speculation")
+    time_generation(llm, prompts, sampling_params)