Return logprob for choices (#87)

examples/usage/choices_logprob.py

@@ -0,0 +1,42 @@
+"""
+python -m sglang.launch_server --model-path meta-llama/Llama-2-7b-chat-hf --port 30000
+"""
+
+import sglang as sgl
+
+
+@sgl.function
+def tool_use(s, question):
+    s += "To answer this question: " + question + ", "
+    s += "I need to use a " + sgl.gen("tool", choices=["calculator", "search engine"])
+
+
+def main():
+    # Run one case
+    question = "What is 5 + 5?"
+    state = tool_use.run(question)
+    print("questions:", question)
+    print("choice:", state["tool"])
+    meta_info = state.get_meta_info("tool")
+    print("logprobs of choice 1", meta_info["prompt_logprob"][0])
+    print("logprobs of choice 2", meta_info["prompt_logprob"][1])
+    print('-' * 50)
+
+    # Run a batch
+    questions = [
+        "What is 5 + 6?",
+        "Who is Michael Jordan?",
+    ]
+    states = tool_use.run_batch([{"question": q} for q in questions])
+    for question, state in zip(questions, states):
+        print("questions:", question)
+        print("choice:", state["tool"])
+        meta_info = state.get_meta_info("tool")
+        print("logprobs of choice 1", meta_info["prompt_logprob"][0])
+        print("logprobs of choice 2", meta_info["prompt_logprob"][1])
+        print('-' * 50)
+
+
+if __name__ == "__main__":
+    sgl.set_default_backend(sgl.RuntimeEndpoint("http://localhost:30000"))
+    main()