[Feature] Add load generation config from model (#11164)

Signed-off-by: liuyanyi <wolfsonliu@163.com>
Signed-off-by: Yanyi Liu <wolfsonliu@163.com>
Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
Co-authored-by: Cyrus Leung <tlleungac@connect.ust.hk>

examples/offline_inference_with_default_generation_config.py

@@ -0,0 +1,30 @@
+from vllm import LLM
+
+# Sample prompts.
+prompts = [
+    "Hello, my name is",
+    "The president of the United States is",
+    "The capital of France is",
+    "The future of AI is",
+]
+
+# Create an LLM with built-in default generation config.
+# The generation config is set to None by default to keep
+# the behavior consistent with the previous version.
+# If you want to use the default generation config from the model,
+# you should set the generation_config to "auto".
+llm = LLM(model="Qwen/Qwen2.5-0.5B-Instruct", generation_config="auto")
+
+# Load the default sampling parameters from the model.
+sampling_params = llm.get_default_sampling_params()
+# Modify the sampling parameters if needed.
+sampling_params.temperature = 0.5
+
+# Generate texts from the prompts. The output is a list of RequestOutput objects
+# that contain the prompt, generated text, and other information.
+outputs = llm.generate(prompts, sampling_params)
+# Print the outputs.
+for output in outputs:
+    prompt = output.prompt
+    generated_text = output.outputs[0].text
+    print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")