rllm中的推理流程

轨项尺 · 6 天前

打印一条推理路径

在上文中，我们跑通了rllm框架，下面，让我们仔细分析一下examples/math_tool/run_math_with_tool.py中的内部过程。
run_math_with_tool.py的大致代码如下：

agent_args = {"tools": ["python"], "parser_name": "qwen", "system_prompt": "You are a math assistant that can write python to solve math problems."}
env_args = {
"tools": ["python"],
"reward_fn": math_reward_fn,
}
engine = AgentExecutionEngine(
agent_class=ToolAgent,
agent_args=agent_args,
env_class=ToolEnvironment,
env_args=env_args,
engine_name="openai",
rollout_engine_args={"base_url": "http://localhost:30000/v1", "api_key": "None"},
tokenizer=tokenizer,
sampling_params=sampling_params,
max_response_length=16384,
max_prompt_length=2048,
n_parallel_agents=n_parallel_agents,
)
test_dataset = DatasetRegistry.load_dataset("aime2024", "test")
...
tasks = test_dataset.repeat(n=8) # repeat to evaluate pass@k
...
results = asyncio.run(engine.execute_tasks(tasks[:5])) # 只跑前10条

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我们打印出一条推理路径看看效果

first_traj = results[0]
print("\n======= 示例轨迹 =======")
print("问题:", first_traj.task)
for i, step in enumerate(first_traj.steps):
print(f"\n--- Step {i} ---")
print("Observation:", step.observation)
print("Model response:", step.model_response)
print("Action:", step.action)
print("Reward:", step.reward)
print("Done:", step.done)
print("======================\n")

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打印出来的结果为（一共有5步，第0步为LLM接受问题；第5步为LLM输出答案，中间步骤都是根据工具调用结果生成推理的过程。Observation是模型接受到的信息，包括问题，工具调用结果等；Action是模型产生的动作，包括工具调用，最终回复等）

问题: {'id': 60, 'problem': '...', 'answer': '204', 'url': '...', 'year': '2024', 'question': 'Every morning Aya goes for a $9$-kilometer-long walk and stops at a coffee shop afterwards. When she walks at a constant speed of $s$ kilometers per hour, the walk takes her 4 hours, including $t$ minutes spent in the coffee shop. When she walks $s+2$ kilometers per hour, the walk takes her 2 hours and 24 minutes, including $t$ minutes spent in the coffee shop. Suppose Aya walks at $s+\\frac{1}{2}$ kilometers per hour. Find the number of minutes the walk takes her, including the $t$ minutes spent in the coffee shop.', 'ground_truth': '204', 'data_source': 'math'}
--- Step 0 ---
Observation: {'id': 60, 'problem': '...', 'answer': '204', 'url': '...', 'year': '2024', 'question': 'Every morning Aya goes for a $9$-kilometer-long walk and stops at a coffee shop afterwards. When she walks at a constant speed of $s$ kilometers per hour, the walk takes her 4 hours, including $t$ minutes spent in the coffee shop. When she walks $s+2$ kilometers per hour, the walk takes her 2 hours and 24 minutes, including $t$ minutes spent in the coffee shop. Suppose Aya walks at $s+\\frac{1}{2}$ kilometers per hour. Find the number of minutes the walk takes her, including the $t$ minutes spent in the coffee shop.', 'ground_truth': '204', 'data_source': 'math'}
Model response:
....
<tool_call>
{"name": "python", "arguments": {"code": "import math\n\na = 1\nb = 2\nc = -11.25\n\ndiscriminant = b**2 - 4*a*c\nsqrt_discriminant = math.sqrt(discriminant)\ns1 = (-b + sqrt_discriminant) / (2*a)\ns2 = (-b - sqrt_discriminant) / (2*a)\n\nprint(s1, s2)"}}
</tool_call>
Action: [{'id': '5c7285c2-d967-4e60-a228-7947d8c87524', 'type': 'function', 'function': {'name': 'python', 'arguments': '{"code": "import math\\n\\na = 1\\nb = 2\\nc = -11.25\\n\\ndiscriminant = b**2 - 4*a*c\\nsqrt_discriminant = math.sqrt(discriminant)\\ns1 = (-b + sqrt_discriminant) / (2*a)\\ns2 = (-b - sqrt_discriminant) / (2*a)\\n\\nprint(s1, s2)"}'}}]
Reward: 0
Done: False
--- Step 1 ---
Observation: {'tool_outputs': {'5c7285c2-d967-4e60-a228-7947d8c87524': '2.5 -4.5\n'}}
Model response:
...
<tool_call>
{"name": "python", "arguments": {"code": "s = 2.5\n\n# Calculate t using equation (1)\nt = (4 - (9 / s)) * 60\nprint(t)"}}
</tool_call>
Action: [{'id': '6e6fc722-29c4-4806-917a-933e7ff87d1b', 'type': 'function', 'function': {'name': 'python', 'arguments': '{"code": "s = 2.5\\n\\n# Calculate t using equation (1)\\nt = (4 - (9 / s)) * 60\\nprint(t)"}'}}]
Reward: 0
Done: False
--- Step 2 ---
...
--- Step 3 ---
...
--- Step 4 ---
Observation: {'tool_outputs': {'dc3840b8-3d86-477e-b51e-32a26ad668d4': 's = 2.5 km/h\nt = 23.999999999999993 minutes\nTotal time for third scenario: 204.0 minutes\n'}}
Model response:
...
### Final Answer:
$$
\boxed{204}
$$
Action: [{'id': 'b35c758b-ce5d-4f8b-a412-5b7fd86cf383', 'type': 'function', 'function': {'name': 'finish', 'arguments': {'response': "<think>\nOkay, let me check the output again. The code output shows that s is 2.5 km/h, t is approximately 24 minutes (due to floating-point precision), and the total time for the third scenario is exactly 204 minutes. That matches our manual calculations. So the answer is 204 minutes.\n\nThe slight discrepancy in t is because of how floating-point numbers are handled in Python, but since t was originally calculated as 24 minutes, the total time comes out perfectly as 204 minutes when converted. Therefore, the final answer should be 204 minutes.\n</think>\n\nThe number of minutes the walk takes Aya, including the $ t $ minutes spent in the coffee shop, when she walks at $ s + \\frac{1}{2} $ kilometers per hour, is **204 minutes**.\n\n### Step-by-Step Explanation:\n1. **Define Variables:**\n - Let $ s $ be Aya's walking speed (km/h).\n - Let $ t $ be the time spent in the coffee shop (minutes).\n\n2. **Set Up Equations:**\n - **First Scenario:** \n Walking time: $ \\frac{9}{s} $ hours. \n Total time: $ \\frac{9}{s} + \\frac{t}{60} = 4 $ hours. \n Equation: $ \\frac{9}{s} + \\frac{t}{60} = 4 $.\n\n - **Second Scenario:** \n Walking time: $ \\frac{9}{s+2} $ hours. \n Total time: $ \\frac{9}{s+2} + \\frac{t}{60} = 2.4 $ hours. \n Equation: $ \\frac{9}{s+2} + \\frac{t}{60} = 2.4 $.\n\n3. **Solve for $ s $ and $ t $:**\n - Subtract the second equation from the first: \n $ \\frac{9}{s} - \\frac{9}{s+2} = 1.6 $. \n Simplify: $ \\frac{18}{s(s+2)} = 1.6 $. \n Solve: $ s^2 + 2s - 11.25 = 0 $. \n Roots: $ s = 2.5 $ km/h (discarding the negative root).\n\n - Substitute $ s = 2.5 $ into the first equation: \n $ \\frac{9}{2.5} + \\frac{t}{60} = 4 $. \n Solve: $ t = 24 $ minutes.\n\n4. **Third Scenario:**\n - Speed: $ s + 0.5 = 3 $ km/h. \n - Walking time: $ \\frac{9}{3} = 3 $ hours. \n - Total time: $ 3 + \\frac{24}{60} = 3.4 $ hours = $ 204 $ minutes.\n\n### Final Answer:\n$$\n\\boxed{204}\n$$"}}}]
Reward: 1.0
Done: True
======================

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由此，我们可以分析出来rllm中Agent 工具调用的流程：

agent观察到问题后，思考并进行function call
rllm框架识别到工具调用操作后，执行工具，并返回结果
Agent根据工具返回的结果继续分析。

此外，在正式讲解代码之前，还要明确几个术语：

环境：负责将问题传递给Agent+执行工具
观察：告诉Agent当前时刻的信息（包括接受到的问题，工具执行结果等）
动作：Agent给环境的指令，也就是Agent生成的工具调用的参数
奖励：这一步表现的好不好

举个例子，Agent调用代码工具，首先要从环境中接受到用户问题，然后Agent从环境中接受（观察）到问题，生成思考，思考后生成代码工具的调用参数（中包裹的内容，也就是Agent的动作）。然后在环境中执行Agent生成的代码，将执行结果返回给Agent，Agent观察到结果后，继续进行分析。
下面，我们对环境，和环境交互的Agent，以及奖励进行分析。至于AgentExecutionEngine本身，则是起到了统一协调的作用。
环境

定义在rllm.environments.tools.tool_env中，用于接受用户输入和执行工具调用。
主要代码如下：

class ToolEnvironment(BaseEnv):
def step(self, action: list[dict] | str | dict):
"""
Take a step in the environment based on the action.
Args:
actions: List containing a single action string from the agent
Returns:
next_observations, rewards, terminateds, infos
"""
# 检查action中是否有finish字段（如果当前找不到任何工具调用的动作，那么Agent就会执行finish动作，并传入到环境中），如果有，代表回答完成
if isinstance(action, list) and action:
for tool_call in action:
if tool_call.get("function", {}).get("name") == "finish":
done = True
break
# 如果回答完成，那么提取llm的回答，并且计算奖励
if done:
# 提取llm的回答
if isinstance(action, str):
llm_response = action
elif isinstance(action, list):
...
# 根据问题，真实值和llm的回答计算奖励
task_info = self.task if self.task is not None else {}
reward_output = self.reward_fn(task_info=task_info, action=llm_response)
return {}, reward_output.reward, done, {"response": action, "metadata": reward_output.metadata, "is_correct": reward_output.is_correct}
# 如果回答没有完成，那么执行工具并返回工具执行结果
tool_calls = action
tool_outputs = self._execute_tool_calls(tool_calls) # 执行工具是，会调用工具类的call方法（一般定义在rllm/tools 文件夹中）
next_obs = {"tool_outputs": tool_outputs}
# Return results as lists with single items to maintain batch structure
return next_obs, reward, done, {"response": action, "metadata": {}}

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Agent

Agent主要用来维护一个消息队列，其中内容包括系统提示词，用户输入，模型回复以及工具调用

[
{"role": "system", "content": ""},
{"role": "user", "content": ""},
{"role": "assistant", "content": ""},
{"role": "tool", "content": "","tool_call_id": ""}
....
....
]

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class ToolAgent(BaseAgent):
def _format_observation_as_messages(self, obs: Any) -> list[dict]:
"""格式化从环境中接收到的观察"""
messages = []
if isinstance(obs, dict):
# 如果有question字段，代表是用户传入的，将role设为user，加入到历史消息中
if "question" in obs:
messages.append({"role": "user", "content": obs["question"]})
# 如果有tool_outputs字段，代表是工具返回结果，将role设为tool，加入到历史消息中
elif "tool_outputs" in obs:
# Format tool outputs from environment observation
for tool_call_id, tool_output_str in obs["tool_outputs"].items():
messages.append(
{
"role": "tool",
"content": tool_output_str,
"tool_call_id": tool_call_id,
})
elif isinstance(obs, str):
messages.append({"role": "user", "content": obs})
elif obs:
messages.append({"role": "user", "content": str(obs)})
return messages
def update_from_env(self, observation: Any, reward: float, done: bool, info: dict, **kwargs):
"""
将环境中获取到的观察加入到消息队列中
"""
obs_messages = self._format_observation_as_messages(observation)
self.messages.extend(obs_messages)
def update_from_model(self, response: str, **kwargs) -> Action:
"""
从response中解析模型生成的工具调用参数
"""
tool_calls_dict = []
assistant_content = response
# 从模型响应中解析回答
try:
tool_calls = self.tool_parser.parse(response)
tool_calls_dict = [
{
"id": str(uuid.uuid4()),
"type": "function",
"function": tool_call.to_dict(),
}
for tool_call in tool_calls
]
# 将模型的完整响应加入到消息队列中
assistant_message = {"role": "assistant", "content": assistant_content}
if len(tool_calls_dict) > 0:
# 进行简单的格式转换
...
# 如果没有工具调用，那么将当前的动作设置为finish
else:
tool_calls_dict = [
{
"id": str(uuid.uuid4()),
"type": "function",
"function": {
"name": "finish",
"arguments": {
"response": assistant_content,
},
},
}
]
# 将模型的响应加入到消息队列中
self.messages.append(assistant_message)
return Action(action=tool_calls_dict)
def reset(self):
"""初始化（设置system prompt）"""
self.messages = [{"role": "system", "content": self.system_prompt + self.tools_prompt}]

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Agent执行引擎

代码在rllm/engine/agent_execution_engine.py中（为了简化起见，这里面移除了很多并行和状态维护的代码）。
可以看到，Agent执行引擎用于协调Agent和环境，实现了ReAct的推理模式。

class AgentExecutionEngine:
async def run_agent_trajectory_async(self, idx, application_id, seed=0, mode="Text", **kwargs):
"""执行Agent推理的代码"""
# 初始化
env.reset()
agent.reset()
for step_idx in range(self.max_steps):
# 拿到prompt
prompt_messages = agent.chat_completions.copy()
# 得到response
response = self.get_model_response(prompt_messages, application_id, **kwargs)
# 从response中解析出动作
action: Action = agent.update_from_model(response)
action = action.action
# 执行动作
env.step(action)
# Agent更新
agent.update_from_env(...)
# 执行完成后跳出循环
if done:
break

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奖励函数

奖励函数定义在rllm/rewards/math_reward.py中，这里只使用了正确性奖励，主要代码如下：

class RewardMathFn:
def __call__(self, task_info: dict, action: str) -> RewardOutput:
model_response = action
# 剔除<think></think>标签里面的内容
if THOUGHT_DELIMITER_END in model_response:
model_solution = model_response.split(THOUGHT_DELIMITER_END)[1]
else:
model_solution = model_response
# 提取模型的回答（一般都包裹在\box{}中）
model_answer = extract_answer(model_solution)
# 获取真实标签
ground_truths = task_info.get("ground_truth", None)
# 从真实标签中的\boxed字段里提取答案
processed_ground_truths = []
for truth in ground_truths:
truth = str(truth)
if "\\boxed" in truth:
processed_truth = extract_answer(truth)
if processed_truth is not None:
processed_ground_truths.append(processed_truth)
else:
processed_ground_truths.append(truth)
# 设置正确性奖励
for ground_truth in processed_ground_truths:
# 模型回答是否正确？
is_correct = grade_answer_mathd(model_answer, ground_truth) or grade_answer_sympy(model_answer, ground_truth)
if is_correct:
# 设置正确性奖励
reward = self.config.correct_reward
return RewardOutput(reward=reward, is_correct=True)
# 模型回答错误
return RewardOutput(reward=self.config.incorrect_reward, is_correct=False)

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