如何使用少量示例

在本指南中，我们将学习如何创建一个简单的提示模板，在生成时为模型提供示例输入和输出。给定 LLM 几个这样的示例被称为少量示例（few-shotting），是一种简单而强大的引导生成的方法，在某些情况下可以显著提升模型性能。

少量示例提示模板可以从一组示例构建，或者通过一个示例选择器类来构建，该类负责从已定义的示例集合中选择子集。

本指南将介绍使用字符串提示模板的少量示例方法。关于针对聊天模型使用聊天消息进行少量示例的指南，请参见此处。

预备知识

本指南假设您已熟悉以下概念：

• 提示模板
• 示例选择器
• LLMs
• 向量存储

为少量示例创建一个格式化工具

配置一个将少量示例格式化为字符串的格式化工具。此格式化工具应为一个 PromptTemplate 对象。

import { PromptTemplate } from "@langchain/core/prompts";

const examplePrompt = PromptTemplate.fromTemplate(
  "Question: {question}\n{answer}"
);

创建示例集

接下来，我们将创建一个少量示例的列表。每个示例应是一个字典，表示我们上面定义的格式化提示的示例输入。

const examples = [
  {
    question: "Who lived longer, Muhammad Ali or Alan Turing?",
    answer: `
  Are follow up questions needed here: Yes.
  Follow up: How old was Muhammad Ali when he died?
  Intermediate answer: Muhammad Ali was 74 years old when he died.
  Follow up: How old was Alan Turing when he died?
  Intermediate answer: Alan Turing was 41 years old when he died.
  So the final answer is: Muhammad Ali
  `,
  },
  {
    question: "When was the founder of craigslist born?",
    answer: `
  Are follow up questions needed here: Yes.
  Follow up: Who was the founder of craigslist?
  Intermediate answer: Craigslist was founded by Craig Newmark.
  Follow up: When was Craig Newmark born?
  Intermediate answer: Craig Newmark was born on December 6, 1952.
  So the final answer is: December 6, 1952
  `,
  },
  {
    question: "Who was the maternal grandfather of George Washington?",
    answer: `
  Are follow up questions needed here: Yes.
  Follow up: Who was the mother of George Washington?
  Intermediate answer: The mother of George Washington was Mary Ball Washington.
  Follow up: Who was the father of Mary Ball Washington?
  Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
  So the final answer is: Joseph Ball
  `,
  },
  {
    question:
      "Are both the directors of Jaws and Casino Royale from the same country?",
    answer: `
  Are follow up questions needed here: Yes.
  Follow up: Who is the director of Jaws?
  Intermediate Answer: The director of Jaws is Steven Spielberg.
  Follow up: Where is Steven Spielberg from?
  Intermediate Answer: The United States.
  Follow up: Who is the director of Casino Royale?
  Intermediate Answer: The director of Casino Royale is Martin Campbell.
  Follow up: Where is Martin Campbell from?
  Intermediate Answer: New Zealand.
  So the final answer is: No
  `,
  },
];

将示例和格式化器传递给 FewShotPromptTemplate

最后，创建一个 FewShotPromptTemplate 对象。该对象接收少量样本示例和用于格式化这些示例的格式化器。当此 FewShotPromptTemplate 被格式化时，它会使用 examplePrompt 格式化传入的示例，然后将它们添加到最终提示中的 suffix 之前：

import { FewShotPromptTemplate } from "@langchain/core/prompts";

const prompt = new FewShotPromptTemplate({
  examples,
  examplePrompt,
  suffix: "Question: {input}",
  inputVariables: ["input"],
});

const formatted = await prompt.format({
  input: "Who was the father of Mary Ball Washington?",
});
console.log(formatted.toString());

Question: Who lived longer, Muhammad Ali or Alan Turing?

  Are follow up questions needed here: Yes.
  Follow up: How old was Muhammad Ali when he died?
  Intermediate answer: Muhammad Ali was 74 years old when he died.
  Follow up: How old was Alan Turing when he died?
  Intermediate answer: Alan Turing was 41 years old when he died.
  So the final answer is: Muhammad Ali


Question: When was the founder of craigslist born?

  Are follow up questions needed here: Yes.
  Follow up: Who was the founder of craigslist?
  Intermediate answer: Craigslist was founded by Craig Newmark.
  Follow up: When was Craig Newmark born?
  Intermediate answer: Craig Newmark was born on December 6, 1952.
  So the final answer is: December 6, 1952


Question: Who was the maternal grandfather of George Washington?

  Are follow up questions needed here: Yes.
  Follow up: Who was the mother of George Washington?
  Intermediate answer: The mother of George Washington was Mary Ball Washington.
  Follow up: Who was the father of Mary Ball Washington?
  Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
  So the final answer is: Joseph Ball


Question: Are both the directors of Jaws and Casino Royale from the same country?

  Are follow up questions needed here: Yes.
  Follow up: Who is the director of Jaws?
  Intermediate Answer: The director of Jaws is Steven Spielberg.
  Follow up: Where is Steven Spielberg from?
  Intermediate Answer: The United States.
  Follow up: Who is the director of Casino Royale?
  Intermediate Answer: The director of Casino Royale is Martin Campbell.
  Follow up: Where is Martin Campbell from?
  Intermediate Answer: New Zealand.
  So the final answer is: No


Question: Who was the father of Mary Ball Washington?

通过向模型提供这样的示例，我们可以引导模型生成更优的回答。

使用示例选择器

我们将重用前面章节中的示例集和格式化程序。不过，这次不会将示例直接提供给 FewShotPromptTemplate 对象，而是将它们提供给一个名为 SemanticSimilarityExampleSelector 的 ExampleSelector 实现实例。此类会根据初始集合中示例与输入内容的相似性来选择少量示例。它使用嵌入模型计算输入与少量示例之间的相似性，并使用向量存储来进行最近邻搜索。

为了展示其效果，我们先单独初始化一个实例并调用它：

为嵌入模型设置您的 OpenAI API 密钥

export OPENAI_API_KEY="..."

import { SemanticSimilarityExampleSelector } from "@langchain/core/example_selectors";
import { MemoryVectorStore } from "langchain/vectorstores/memory";
import { OpenAIEmbeddings } from "@langchain/openai";

const exampleSelector = await SemanticSimilarityExampleSelector.fromExamples(
  // This is the list of examples available to select from.
  examples,
  // This is the embedding class used to produce embeddings which are used to measure semantic similarity.
  new OpenAIEmbeddings(),
  // This is the VectorStore class that is used to store the embeddings and do a similarity search over.
  MemoryVectorStore,
  {
    // This is the number of examples to produce.
    k: 1,
  }
);

// Select the most similar example to the input.
const question = "Who was the father of Mary Ball Washington?";
const selectedExamples = await exampleSelector.selectExamples({ question });
console.log(`Examples most similar to the input: ${question}`);
for (const example of selectedExamples) {
  console.log("\n");
  console.log(
    Object.entries(example)
      .map(([k, v]) => `${k}: ${v}`)
      .join("\n")
  );
}

Examples most similar to the input: Who was the father of Mary Ball Washington?


question: Who was the maternal grandfather of George Washington?
answer:
  Are follow up questions needed here: Yes.
  Follow up: Who was the mother of George Washington?
  Intermediate answer: The mother of George Washington was Mary Ball Washington.
  Follow up: Who was the father of Mary Ball Washington?
  Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
  So the final answer is: Joseph Ball

现在，让我们创建一个 FewShotPromptTemplate 对象。该对象接收示例选择器和用于少量示例的格式化提示。

const prompt = new FewShotPromptTemplate({
  exampleSelector,
  examplePrompt,
  suffix: "Question: {input}",
  inputVariables: ["input"],
});

const formatted = await prompt.invoke({
  input: "Who was the father of Mary Ball Washington?",
});
console.log(formatted.toString());

Question: Who was the maternal grandfather of George Washington?

  Are follow up questions needed here: Yes.
  Follow up: Who was the mother of George Washington?
  Intermediate answer: The mother of George Washington was Mary Ball Washington.
  Follow up: Who was the father of Mary Ball Washington?
  Intermediate answer: The father of Mary Ball Washington was Joseph Ball.
  So the final answer is: Joseph Ball


Question: Who was the father of Mary Ball Washington?

下一步

你现在已经学会了如何向提示中添加少量示例。

接下来，请查看本节中有关提示模板的其他操作指南、关于使用聊天模型进行少量示例的相关操作指南，或示例选择器操作指南的其他内容。