【LangChain系列 15】语言模型—

原文地址：【LangChain系列 15】语言模型——LLMs(一)

本文速读：

异步API
自定义LLM
Fake LLM
HumanInput LLM

本文将介绍LLMs在LangChain中的一些用法，帮助我们更好地了解LLM模块。

01 异步API

LangChain通过异步库实现了对异步的支持，异步对于多LLM的并发调用是非常有用的。目前，OpenAI、PromptLayerOpenAI、ChatOpenAI、Anthropic、Cohere都是支持异步的，其它LLM的异步支持已经在规划中。

在LangChain中，可以通过agenerate方法去异步地调用OpenAI LLM。


import time
import asyncio

from langchain.llms import OpenAI


def generate_serially():
    llm = OpenAI(temperature=0.9)
    for _ in range(10):
        resp = llm.generate(["Hello, how are you?"])
        print(resp.generations[0][0].text)


async def async_generate(llm):
    resp = await llm.agenerate(["Hello, how are you?"])
    print(resp.generations[0][0].text)


async def generate_concurrently():
    llm = OpenAI(temperature=0.9)
    tasks = [async_generate(llm) for _ in range(10)]
    await asyncio.gather(*tasks)


s = time.perf_counter()
# If running this outside of Jupyter, use asyncio.run(generate_concurrently())
await generate_concurrently()
elapsed = time.perf_counter() - s
print(f"Concurrent executed in {elapsed:0.2f} seconds.")

s = time.perf_counter()
generate_serially()
elapsed = time.perf_counter() - s
print(f"Serial executed in {elapsed:0.2f} seconds.")

执行代码，输出结果：

I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, how about you?
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about yourself?
  
  
  I'm doing well, thank you! How about you?
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you! How about you?
  
  
  I'm doing well, thank you. How about you?
  Concurrent executed in 1.39 seconds.
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about you?
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about yourself?
  
  
  I'm doing well, thanks for asking. How about you?
  
  
  I'm doing well, thanks! How about you?
  
  
  I'm doing well, thank you. How about you?
  
  
  I'm doing well, thank you. How about yourself?
  
  
  I'm doing well, thanks for asking. How about you?
  Serial executed in 5.77 seconds.

02 自定义LLM

通过自定义LLM，你可以定义一个自己的LLM，也可以基于LangChain已有的LLM封装成一个新的LLM。

封装一个LLM，你唯一要实现的方法是_call，这个方法接收一个字符串和一些可选的停止词，然后返回一个字符串；另外，还有一个可选的_identifying_params属性，你可以根据需要决定是否实现，它主要作用是辅助这个类信息的打印输出。

下面我们动手实现一个自定义的LLM。

from typing import Any, List, Mapping, Optional

from langchain.callbacks.manager import CallbackManagerForLLMRun
from langchain.llms.base import LLM

class CustomLLM(LLM):
    n: int

    @property
    def _llm_type(self) -> str:
        return "custom"

    def _call(
        self,
        prompt: str,
        stop: Optional[List[str]] = None,
        run_manager: Optional[CallbackManagerForLLMRun] = None,
        **kwargs: Any,
    ) -> str:
        if stop is not None:
            raise ValueError("stop kwargs are not permitted.")
        return prompt[: self.n]

    @property
    def _identifying_params(self) -> Mapping[str, Any]:
        """Get the identifying parameters."""
        return {"n": self.n}

这样就定义好了一个LLM，接下来就可以使用它了。

llm = CustomLLM(n=10)
llm("This is a foobar thing"

我们可以输出这个类的对象，查看它的打印输出：

print(llm)

  CustomLLM
  Params: {'n': 10}

因为我们实现了_identifying_params，所以在打印输出这个对象时，输出了相应的属性。

03 Fake LLM

LangChain提供了一个伪造的LLM类可以用来调试，通过模拟调用LLM，当LLM以某种方式返回时，模拟后续会发生什么。

下面我们通过agent的方式使用FakeLLM。


from langchain.llms.fake import FakeListLLM
from langchain.agents import load_tools
from langchain.agents import initialize_agent
from langchain.agents import AgentType

tools = load_tools(["python_repl"])
responses = ["Action: Python REPL\nAction Input: print(2 + 2)", "Final Answer: 4"]
llm = FakeListLLM(responses=responses)
agent = initialize_agent(
    tools, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION, verbose=True
)
agent.run("whats 2 + 2")

执行代码，输出结果：

  > Entering new AgentExecutor chain...
  Action: Python REPL
  Action Input: print(2 + 2)
  Observation: Python REPL is not a valid tool, try one of [Python_REPL].
  
  Thought:Final Answer: 4
  
  > Finished chain.

04 HumanInput LLM

和FakeLLM类似，HumanInput LLM也是一个伪LLM类，可以用来测试、调试等。也是通过模拟调用LLM，然后模拟人类会如何响应。

同样我们通过agent的方式使用HumanInputLLM。

由于需要用到wikipedia，首先安装一下：

pip install wikipedia

然后创建HumanInputLLM。


from langchain.llms.human import HumanInputLLM
from langchain.agents import load_tools
from langchain.agents import initialize_agent
from langchain.agents import AgentType

tools = load_tools(["wikipedia"])
llm = HumanInputLLM(
    prompt_func=lambda prompt: print(
        f"\n===PROMPT====\n{prompt}\n=====END OF PROMPT======"
    )
)
agent = initialize_agent(
    tools, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION, verbose=True
)
agent.run("What is 'Bocchi the Rock!'?")

运行代码，输出结果：

> Entering new AgentExecutor chain...
    
    ===PROMPT====
    Answer the following questions as best you can. You have access to the following tools:
    
    Wikipedia: A wrapper around Wikipedia. Useful for when you need to answer general questions about people, places, companies, historical events, or other subjects. Input should be a search query.
    
    Use the following format:
    
    Question: the input question you must answer
    Thought: you should always think about what to do
    Action: the action to take, should be one of [Wikipedia]
    Action Input: the input to the action
    Observation: the result of the action
    ... (this Thought/Action/Action Input/Observation can repeat N times)
    Thought: I now know the final answer
    Final Answer: the final answer to the original input question
    
    Begin!
    
    Question: What is 'Bocchi the Rock!'?
    Thought:
    =====END OF PROMPT======
    I need to use a tool.
    Action: Wikipedia
    Action Input: Bocchi the Rock!, Japanese four-panel manga and anime series.
    Observation: Page: Bocchi the Rock!
    Summary: Bocchi the Rock! (ぼっち・ざ・ろっく!, Bocchi Za Rokku!) is a Japanese four-panel manga series written and illustrated by Aki Hamaji. It has been serialized in Houbunsha's seinen manga magazine Manga Time Kirara Max since December 2017. Its chapters have been collected in five tankōbon volumes as of November 2022.
    An anime television series adaptation produced by CloverWorks aired from October to December 2022. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim.
    
    Page: Manga Time Kirara
    Summary: Manga Time Kirara (まんがタイムきらら, Manga Taimu Kirara) is a Japanese seinen manga magazine published by Houbunsha which mainly serializes four-panel manga. The magazine is sold on the ninth of each month and was first published as a special edition of Manga Time, another Houbunsha magazine, on May 17, 2002. Characters from this magazine have appeared in a crossover role-playing game called Kirara Fantasia.
    
    Page: Manga Time Kirara Max
    Summary: Manga Time Kirara Max (まんがタイムきららMAX) is a Japanese four-panel seinen manga magazine published by Houbunsha. It is the third magazine of the "Kirara" series, after "Manga Time Kirara" and "Manga Time Kirara Carat". The first issue was released on September 29, 2004. Currently the magazine is released on the 19th of each month.
    Thought:
    ===PROMPT====
    Answer the following questions as best you can. You have access to the following tools:
    
    Wikipedia: A wrapper around Wikipedia. Useful for when you need to answer general questions about people, places, companies, historical events, or other subjects. Input should be a search query.
    
    Use the following format:
    
    Question: the input question you must answer
    Thought: you should always think about what to do
    Action: the action to take, should be one of [Wikipedia]
    Action Input: the input to the action
    Observation: the result of the action
    ... (this Thought/Action/Action Input/Observation can repeat N times)
    Thought: I now know the final answer
    Final Answer: the final answer to the original input question
    
    Begin!
    
    Question: What is 'Bocchi the Rock!'?
    Thought:I need to use a tool.
    Action: Wikipedia
    Action Input: Bocchi the Rock!, Japanese four-panel manga and anime series.
    Observation: Page: Bocchi the Rock!
    Summary: Bocchi the Rock! (ぼっち・ざ・ろっく!, Bocchi Za Rokku!) is a Japanese four-panel manga series written and illustrated by Aki Hamaji. It has been serialized in Houbunsha's seinen manga magazine Manga Time Kirara Max since December 2017. Its chapters have been collected in five tankōbon volumes as of November 2022.
    An anime television series adaptation produced by CloverWorks aired from October to December 2022. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim.
    
    Page: Manga Time Kirara
    Summary: Manga Time Kirara (まんがタイムきらら, Manga Taimu Kirara) is a Japanese seinen manga magazine published by Houbunsha which mainly serializes four-panel manga. The magazine is sold on the ninth of each month and was first published as a special edition of Manga Time, another Houbunsha magazine, on May 17, 2002. Characters from this magazine have appeared in a crossover role-playing game called Kirara Fantasia.
    
    Page: Manga Time Kirara Max
    Summary: Manga Time Kirara Max (まんがタイムきららMAX) is a Japanese four-panel seinen manga magazine published by Houbunsha. It is the third magazine of the "Kirara" series, after "Manga Time Kirara" and "Manga Time Kirara Carat". The first issue was released on September 29, 2004. Currently the magazine is released on the 19th of each month.
    Thought:
    =====END OF PROMPT======
    These are not relevant articles.
    Action: Wikipedia
    Action Input: Bocchi the Rock!, Japanese four-panel manga series written and illustrated by Aki Hamaji.
    Observation: Page: Bocchi the Rock!
    Summary: Bocchi the Rock! (ぼっち・ざ・ろっく!, Bocchi Za Rokku!) is a Japanese four-panel manga series written and illustrated by Aki Hamaji. It has been serialized in Houbunsha's seinen manga magazine Manga Time Kirara Max since December 2017. Its chapters have been collected in five tankōbon volumes as of November 2022.
    An anime television series adaptation produced by CloverWorks aired from October to December 2022. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim.
    Thought:
    ===PROMPT====
    Answer the following questions as best you can. You have access to the following tools:
    
    Wikipedia: A wrapper around Wikipedia. Useful for when you need to answer general questions about people, places, companies, historical events, or other subjects. Input should be a search query.
    
    Use the following format:
    
    Question: the input question you must answer
    Thought: you should always think about what to do
    Action: the action to take, should be one of [Wikipedia]
    Action Input: the input to the action
    Observation: the result of the action
    ... (this Thought/Action/Action Input/Observation can repeat N times)
    Thought: I now know the final answer
    Final Answer: the final answer to the original input question
    
    Begin!
    
    Question: What is 'Bocchi the Rock!'?
    Thought:I need to use a tool.
    Action: Wikipedia
    Action Input: Bocchi the Rock!, Japanese four-panel manga and anime series.
    Observation: Page: Bocchi the Rock!
    Summary: Bocchi the Rock! (ぼっち・ざ・ろっく!, Bocchi Za Rokku!) is a Japanese four-panel manga series written and illustrated by Aki Hamaji. It has been serialized in Houbunsha's seinen manga magazine Manga Time Kirara Max since December 2017. Its chapters have been collected in five tankōbon volumes as of November 2022.
    An anime television series adaptation produced by CloverWorks aired from October to December 2022. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim.
    
    Page: Manga Time Kirara
    Summary: Manga Time Kirara (まんがタイムきらら, Manga Taimu Kirara) is a Japanese seinen manga magazine published by Houbunsha which mainly serializes four-panel manga. The magazine is sold on the ninth of each month and was first published as a special edition of Manga Time, another Houbunsha magazine, on May 17, 2002. Characters from this magazine have appeared in a crossover role-playing game called Kirara Fantasia.
    
    Page: Manga Time Kirara Max
    Summary: Manga Time Kirara Max (まんがタイムきららMAX) is a Japanese four-panel seinen manga magazine published by Houbunsha. It is the third magazine of the "Kirara" series, after "Manga Time Kirara" and "Manga Time Kirara Carat". The first issue was released on September 29, 2004. Currently the magazine is released on the 19th of each month.
    Thought:These are not relevant articles.
    Action: Wikipedia
    Action Input: Bocchi the Rock!, Japanese four-panel manga series written and illustrated by Aki Hamaji.
    Observation: Page: Bocchi the Rock!
    Summary: Bocchi the Rock! (ぼっち・ざ・ろっく!, Bocchi Za Rokku!) is a Japanese four-panel manga series written and illustrated by Aki Hamaji. It has been serialized in Houbunsha's seinen manga magazine Manga Time Kirara Max since December 2017. Its chapters have been collected in five tankōbon volumes as of November 2022.
    An anime television series adaptation produced by CloverWorks aired from October to December 2022. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim.
    Thought:
    =====END OF PROMPT======
    It worked.
    Final Answer: Bocchi the Rock! is a four-panel manga series and anime television series. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim.
    
    > Finished chain.



    "Bocchi the Rock! is a four-panel manga series and anime television series. The series has been praised for its writing, comedy, characters, and depiction of social anxiety, with the anime's visual creativity receiving acclaim."

本文小结

本文是LLMs的第一部分，主要介绍了异步API、自定义LLM、FakeLLM和HumanInputLLM。

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