prompt 工程简介

2023-08-14 pv

ChatGPT 火了。

像是一个超越时代的产品。

它功能强大,可以流利地回答你提出的任何问题,而且看起来很像是那么一回事(当然具体的回答质量参差不齐);可以帮助你润色邮件和文章;甚至可以帮你总结一个网页。

总之,这是一个十分强大的工具

而如果想掌握它,最简单的就是看“使用说明书”。

提示工程(Prompt engineering)应运而生。

1. 背景

按照维基百科的解释,

Prompt engineering or prompting is the process of structuring sentences so that they can be interpreted and understood by a generative AI model in such a way that its output is in accord with the user’s intentions.

意思是,提示工程是构建句子的过程,以便生成式 AI 模型理解,使其输出更符合用户意图。

也就是说,如果想从模型中得到准确结果,恰当、准确的 prompt 非常重要。

提示工程指南🔗 提示工程指南也提到,

掌握了提示工程相关技能将有助于用户更好地了解大型语言模型的能力和局限性。

2. 学习

ChatGPT Prompt Engineering for Developers🔗 ChatGPT Prompt Engineering for Developers 吴恩达(Andrew Ng)与 OpenAI 联合推出的入门级课程,一两个小时就能看完。B 站有搬运。

而如果想要更深入了解内部细节,提示工程指南🔗 提示工程指南本开源的书会是个不错的出发点,里面提到了非常多的论文和工具。有兴趣可以尝试。

应该说,提示工程是个实践性比较强的领域,make your hands dirty比只是单纯看视频学得更快。

3. 概要

课程共有 9 集。整体思路很清楚,涉及提示工程的核心原则,常见的任务处理方式和简单技巧。

我之前以为提示工程就是把问题描述清楚,然后丢给 GPT,等着回答。学习后发现其实不然,这里面有很多技巧,我们可以引导,甚至干预 GPT 回答的内容和形式。

3.1 原则

核心原则有两个,

  • Write clear and specific instructions
  • Give the model time to think

简单来说,就是要提供清晰和具体的指令,同时给模型时间“思考”

3.1.1 原则一

如何写出清晰且具体的指令?这里有一些技巧。

  1. 使用分隔符清楚地指示输入的不同部分,分隔符是以下任意一个: ```, """, < >,

  2. 指定结构化的输出,比如可以输出为 HTML 或者 JSON 格式

    prompt = f"""
    Generate a list of three made-up book titles along \
    with their authors and genres.
    Provide them in JSON format with the following keys:
    book_id, title, author, genre.
    """
    response = get_completion(prompt)
    print(response)
  3. 让模型检查是否满足条件(如果…就…)

    text_1 = f"""
    Making a cup of tea is easy! First, you need to get some \
    water boiling. While that's happening, \
    grab a cup and put a tea bag in it. Once the water is \
    hot enough, just pour it over the tea bag. \
    Let it sit for a bit so the tea can steep. After a \
    few minutes, take out the tea bag. If you \
    like, you can add some sugar or milk to taste. \
    And that's it! You've got yourself a delicious \
    cup of tea to enjoy.
    """
    prompt = f"""
    You will be provided with text delimited by triple quotes.
    If it contains a sequence of instructions, \
    re-write those instructions in the following format:
    Step 1 - ...
    Step 2 - …
    Step N - …
    If the text does not contain a sequence of instructions, \
    then simply write \"No steps provided.\"
    \"\"\"{text_1}\"\"\"
    """
    response = get_completion(prompt)
    print("Completion for Text 1:")
    print(response)
  4. 样本提示(通过提供一个或多个样本提示,让模型了解你的真实意图

    prompt = f"""
    Your task is to answer in a consistent style.
    <child>: Teach me about patience.
    <grandparent>: The river that carves the deepest \
    valley flows from a modest spring; the \
    grandest symphony originates from a single note; \
    the most intricate tapestry begins with a solitary thread.
    <child>: Teach me about resilience.
    """
    response = get_completion(prompt)
    print(response)

原则一的核心,就是结构化地表达清楚提问者的意图,同时提供足够多的背景信息。有效信息越多,结果越准确。

因此,提示工程的第一步,是思考清楚问题。

3.1.2 原则二

第二个原则看上去令人困惑。

我本以为是模型计算耗时比较大,要多点耐心。

其实完全不是这个意思。

这里说的是思维链(Chain-of-Thought):将复杂任务拆分成简单的步骤,逐步引导模型逼近最终答案。

Chain-of-Thought Prompting Elicits Reasoning in Large Language Models🔗 Chain-of-Thought Prompting Elicits Reasoning in Large Language Models 篇论文讲得很清楚。

  1. 指定完成任务所需的步骤(有点像是 workflow)

    text = f"""
    Your task is to perform the following actions:
    1 - Summarize the following text delimited by
    <> with 1 sentence.
    2 - Translate the summary into French.
    3 - List each name in the French summary.
    4 - Output a json object that contains the
    following keys: french_summary, num_names.
    Use the following format:
    Text: <text to summarize>
    Summary: <summary>
    Translation: <summary translation>
    Names: <list of names in Italian summary>
    Output JSON: <json with summary and num_names>
    Text: <{text}>
    """
    response = get_completion(prompt_2)
    print("\nCompletion for prompt 2:")
    print(response)
    response = get_completion(prompt_1)
    print("Completion for prompt 1:")
    print(response)
  2. 在得到答案前,让模型自己找到解决方案

    prompt = f"""
    Your task is to determine if the student's solution \
    is correct or not.
    To solve the problem do the following:
    - First, work out your own solution to the problem.
    - Then compare your solution to the student's solution \
    and evaluate if the student's solution is correct or not.
    Don't decide if the student's solution is correct until
    you have done the problem yourself.
    Use the following format:
    Question:
    ```
    question here
    ```
    Student's solution:
    ```
    student's solution here
    ```
    Actual solution:
    ```
    steps to work out the solution and your solution here
    ```
    Is the student's solution the same as actual solution \
    just calculated:
    ```
    yes or no
    ```
    Student grade:
    ```
    correct or incorrect
    ```
    Question:
    ```
    I'm building a solar power installation and I need help \
    working out the financials.
    - Land costs $100 / square foot
    - I can buy solar panels for $250 / square foot
    - I negotiated a contract for maintenance that will cost \
    me a flat $100k per year, and an additional $10 / square \
    foot
    What is the total cost for the first year of operations \
    as a function of the number of square feet.
    ```
    Student's solution:
    ```
    Let x be the size of the installation in square feet.
    Costs:
    1. Land cost: 100x
    2. Solar panel cost: 250x
    3. Maintenance cost: 100,000 + 100x
    Total cost: 100x + 250x + 100,000 + 100x = 450x + 100,000
    ```
    Actual solution:
    """
    response = get_completion(prompt)
    print(response)
3.1.3 模型幻觉(Hallucinations)

这一点不是核心原则,但解释了大语言模型的局限性:并非给出的所有答案都是可信的。

常用 GPT 的人应该都遇到过,有时它会给出一些似是而非的答案。这就比较考验提问者的鉴别能力。

说一个个人在使用中的技巧:把 GPT 当作是一种思维发散的工具,采集足够多可能后借助搜索引擎,将其中的有效信息进行收敛,进而提供给 GPT 更多信息,逐步得到最终答案。

3.2 迭代开发(Iterative Prompt Develelopment)

这个过程,很像是敏捷开发。

我们很难一次就把 prompt 写好,但可以根据反馈迭代:

  • 写一个 prompt,得到回答
  • 检查回答是否满意,不满意的话,修正 prompt
  • 继续提问

简单直接,但很实用。

3.3 常见任务:总结、推理、转换和扩展

ChatGPT 的使用场景广泛,这里列举了四个典型场景:总结;推理;转换;扩展

3.3.1 总结(Summarizing)

面对一大段长文本,我们可以借助 LLM 的总结(summarize)能力快速获取信息。

prompt = f"""
Your task is to generate a short summary of a product \
review from an ecommerce site.
Summarize the review below, delimited by triple
backticks, in at most 30 words.
Review: ```{prod_review}```
"""
response = get_completion(prompt)
print(response)
3.3.2 推理(Inferring)

推理是对文本的另一种分析,例如情感分析。

传统的 NLP 也能做到,但使用 LLM 会更加简单,只需要写个 prompt。连代码都不用写了。

prompt = f"""
What is the sentiment of the following product review,
which is delimited with triple backticks?
Review text: ```{lamp_review}```
"""
response = get_completion(prompt)
print(response)
3.3.3 转换(Transforming)

大语言模型也非常擅长将输入转换为不同的格式,比如翻译,比如拼写纠错等,甚至格式转换,将 HTML 转换为 JSON。

prompt = f"""
proofread and correct this review. Make it more compelling.
Ensure it follows APA style guide and targets an advanced reader.
Output in markdown format.
Text: ```{text}```
"""
response = get_completion(prompt)
display(Markdown(response))
3.3.4 扩展(Expanding)

扩展是将短文本输入到大语言模型中,让模型生成更长的文本。比如,生成基于某个主题的电子邮件,甚至写一篇论文。但目前 科学(Science)杂志并不允许将 ChatGPT 列为作者🔗

prompt = f"""
You are a customer service AI assistant.
Your task is to send an email reply to a valued customer.
Given the customer email delimited by ```, \
Generate a reply to thank the customer for their review.
If the sentiment is positive or neutral, thank them for \
their review.
If the sentiment is negative, apologize and suggest that \
they can reach out to customer service.
Make sure to use specific details from the review.
Write in a concise and professional tone.
Sign the email as `AI customer agent`.
Customer review: ```{review}```
Review sentiment: {sentiment}
"""
response = get_completion(prompt)
print(response)

这里顺带提一句,大语言模型有个“温度(temperature)”参数,被用来描述结果的不确定性。

这个参数很有意思,因为众所周知,温度越高,熵越大,不确定性也就越大。

4. 总结

ChatGPT 是一个强大的工具。这种强大,不仅在于它所能处理的任务种类丰富多样,也在于它对于问题的理解,信息的处理和组织,某种程度上已经超出了我们的预期。

或许在不久的未来,“图灵测试”很快就能通过。

当然,大语言模型的背后,离不开计算机科学的理论创新,半导体行业的”摩尔定律“,日益增长的数据采集和存储。

此刻我们最需要的,就是学习一些简单技巧,更好地使用这些工具,来简化复杂的问题,解放双手。多留一些时间给家人和生活。

毕竟,机器应该工作,人类应该思考。

(完)

参考

  1. https://zh.wikipedia.org/zh-hans/%E6%8F%90%E7%A4%BA%E5%B7%A5%E7%A8%8B🔗
  2. https://www.promptingguide.ai/zh🔗
  3. https://zhuanlan.zhihu.com/p/625917566🔗
  4. datawhalechina🔗
  5. prompt-engineering-for-developers🔗
在 GitHub 上编辑本页面

最后更新于: 2024-06-14T07:17:44+08:00