RAG vs. Fine Tuning ，一种实用方法

作者：来自 Elastic Tomás Murúa

比较 RAG 与 Fine-Tuning 工具，以电子商务聊天机器人为实际示例。

本文通过在虚拟电子商务商店的聊天框场景中，比较检索增强生成（ RAG ）与 Fine-Tuning 的性能，提供了一种实用对比。

本文结构如下：

• RAG 与 Fine-Tuning

• 聊天机器人测试案例： Pear Store

• 方法 1：Fine-Tuning

• 方法 2：RAG

RAG 与 Fine-Tuning

RAG

RAG （检索增强生成）将 大型语言模型（ LLMs ）与信息检索系统结合，使生成的答案能够利用来自知识库的最新和特定数据。

优点：

• RAG 允许使用外部数据，而无需修改基础模型，并提供精确、安全和可追溯的答案。

实现：

• 在 Elasticsearch 中，数据可以使用优化的索引进行语义搜索，并支持文档级安全性。

挑战：

• RAG 依赖外部知识，使得准确性取决于检索到的信息。

• 检索过程可能会受到上下文窗口大小的限制，从而增加成本。

• RAG 还面临集成和隐私挑战，尤其是在不同来源的敏感数据处理方面。

Fine-tuning

Fine-Tuning指的是在特定数据集上训练一个预训练模型的过程。此过程调整模型的内部权重，使其能够学习特定模式并生成定制化的答案。

Fine-Tuning 还可用于模型蒸馏，即用较小的模型学习较大模型的输出，以提升特定任务的性能。这种方法可以在降低成本的同时，利用较大模型的能力。

优点：

• 提供高度优化，使回答适应特定任务，特别适用于知识不经常变化的静态环境或领域。

实现：

• 需要使用结构化数据按照输入-输出格式训练模型。

• OpenAI Fine-Tuning 通过 UI 简化了这一流程，用户可以上传数据集（ JSONL ），然后在受控环境中进行训练和测试。

挑战：

• 重新训练过程耗时且消耗计算资源。

• 精度取决于数据集的质量和规模，数据集过小或不均衡可能会导致答案泛化或偏离上下文。

• 需要专业知识和精力来正确调整。

• 不支持基于用户的个性化数据分割，也缺乏外部知识支撑。

OpenAI 文档建议："我们推荐首先尝试使用 Prompt Engineering、Prompt Chaining（将复杂任务拆分为多个提示）以及 Function Calling 来优化结果......"

Fine-Tuning 与 RAG 对比

方面	Fine-Tuning	RAG
支持的数据	静态	动态
设置成本	高（训练和计算资源消耗大）	低（仅需索引配置）
可扩展性	低，需要重新训练模型	高，可实时更新
更新所需时间	数小时/数天	数分钟
对最新变化的精准度	低（未训练新数据时效果较差）	高（依赖语义搜索获取最新信息）

聊天机器人测试案例：Pear Store

我们将使用一个基于虚拟在线商店 Pear Store 的测试案例。

Pear Store 需要一个助手来回答有关其 政策、促销和产品 的特定问题。这些答案必须 准确、一致 ，符合商店的信息，并且对 员工和顾客 都有帮助。

Fine-Tuning 数据集

我们将使用一个训练数据集，其中包含关于 产品、政策和促销 的特定问题及其答案。例如：

问题： What happens if a product is defective?/如果产品有缺陷怎么办？
答案： If a product is defective, we'll send you a free gift of one kilogram of pears along with the replacement./如果产品有缺陷，我们会免费赠送你 一公斤梨 并提供替换。

RAG 数据集

对于 RAG 的实现，我们将使用相同的数据集，将其转换为 PDF 并通过 Playground 索引到 Elasticsearch 中。

以下是 PDF 文件的内容：

`

1.  Pear Store Q&A

3.  Q: What happens if a product is defective?
4.  A: If a product is defective, we send you a free gift of one kilogram of pears along with the replacement.

6.  Q: What is the special promotion for December?
7.  A: For December, every smartphone purchase comes with a free pair of wireless headphones.

9.  Q: How many models of laptops are in stock?
10.  A: Currently, we have exactly 12 laptop models in stock, including two exclusive limited editions.

12.  Q: What is the policy for damaged packages?
13.  A: If your package arrives damaged, you receive a $25 store credit and priority shipping for your next order.

15.  Q: What do you offer for first-time customers?
16.  A: First-time customers receive a 5% discount and a free coffee mug with their first purchase.

18.  Q: Can I combine discounts with promotions?
19.  A: Unfortunately, discounts and promotions cannot be combined unless explicitly stated.

21.  Q: What is the warranty period for limited edition products?
22.  A: Limited edition products have a 2-year warranty, unlike the standard 1-year warranty.

24.  Q: What is the return window for holiday purchases?
25.  A: Holiday purchases can be returned up to 45 days after the date of purchase.

27.  Q: How do I participate in the customer loyalty program?
28.  A: Sign up for an account on our website to automatically enroll in our loyalty program and start earning points.

30.  Q: What exclusive products are available this season?
31.  A: This season, we are offering exclusive colors for our best-selling laptops and a premium smartphone with enhanced features.

33.  Q: How do I report an issue with my order?
34.  A: You can report an issue by contacting our support team through your account dashboard or by calling our hotline.

36.  Q: Do you offer gift wrapping for products?
37.  A: Yes, we offer gift wrapping for $5 per product during checkout.

39.  Q: How do I apply a discount code?
40.  A: Enter the discount code in the 'Promo Code' section at checkout to apply it to your order.

42.  Q: What shipping methods do you offer?
43.  A: We offer standard, expedited, and same-day delivery options depending on your location.

45.  Q: Are there any products exclusively sold online?
46.  A: Yes, our limited edition headphones and custom accessories are exclusively available online.

48.  Q: What happens if a product is out of stock?
49.  A: If a product is out of stock, you can sign up for a notification to know when it's back.

`AI写代码

方法 1：Fine-Tuning

首先，我们准备数据集，格式为 JSONL，如下所示：

`

1.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What happens if a product is defective?"},{"role":"assistant","content":"If a product is defective, we send you a free gift of one kilogram of pears along with the replacement."}]}
2.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What is the special promotion for December?"},{"role":"assistant","content":"For December, every smartphone purchase comes with a free pair of wireless headphones."}]}
3.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"How many models of laptops are in stock?"},{"role":"assistant","content":"Currently, we have exactly 12 laptop models in stock, including two exclusive limited editions."}]}
4.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What is the policy for damaged packages?"},{"role":"assistant","content":"If your package arrives damaged, you receive a $25 store credit and priority shipping for your next order."}]}
5.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What do you offer for first-time customers?"},{"role":"assistant","content":"First-time customers receive a 5% discount and a free coffee mug with their first purchase."}]}
6.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"Can I combine discounts with promotions?"},{"role":"assistant","content":"Unfortunately, discounts and promotions cannot be combined unless explicitly stated."}]}
7.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What is the warranty period for limited edition products?"},{"role":"assistant","content":"Limited edition products have a 2-year warranty, unlike the standard 1-year warranty."}]}
8.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What is the return window for holiday purchases?"},{"role":"assistant","content":"Holiday purchases can be returned up to 45 days after the date of purchase."}]}
9.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"How do I participate in the customer loyalty program?"},{"role":"assistant","content":"Sign up for an account on our website to automatically enroll in our loyalty program and start earning points."}]}
10.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What exclusive products are available this season?"},{"role":"assistant","content":"This season, we are offering exclusive colors for our best-selling laptops and a premium smartphone with enhanced features."}]}
11.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"How do I report an issue with my order?"},{"role":"assistant","content":"You can report an issue by contacting our support team through your account dashboard or by calling our hotline."}]}
12.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"Do you offer gift wrapping for products?"},{"role":"assistant","content":"Yes, we offer gift wrapping for $5 per product during checkout."}]}
13.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"How do I apply a discount code?"},{"role":"assistant","content":"Enter the discount code in the 'Promo Code' section at checkout to apply it to your order."}]}
14.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What shipping methods do you offer?"},{"role":"assistant","content":"We offer standard, expedited, and same-day delivery options depending on your location."}]}
15.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"Are there any products exclusively sold online?"},{"role":"assistant","content":"Yes, our limited edition headphones and custom accessories are exclusively available online."}]}
16.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"What happens if a product is out of stock?"},{"role":"assistant","content":"If a product is out of stock, you can sign up for a notification to know when it's back."}]}
17.  {"messages":[{"role":"system","content":"You are a helpful assistant for Pear Store, providing specific information about products, promotions, and policies."},{"role":"user","content":"How do I upgrade my product warranty?"},{"role":"assistant","content":"You can purchase an extended warranty during checkout or within 30 days of your purchase."}]}

`AI写代码

确保 JSONL 文件中的每一行都是有效的 JSON 对象，并且没有尾随的逗号。

接下来，使用 OpenAI UI，我们可以进入 Dashboard > Fine-tuning 并点击 Create。

然后，你可以上传我们刚刚创建的 JSONL 文件。

现在点击 Create 开始训练。

训练完成后，你可以点击 Playground ，你将拥有一个方便的界面，可以将 fine-tuned 模型与未经过训练的模型对比，针对特定问题查看结果。

在右侧，我们可以看到模型提供了关于有缺陷产品的自定义答案：a free kilogram of pears along with the replacement。

然而，模型的回答不一致。随后的相同问题尝试得出了意外的答案。

尽管 fine-tuning 允许我们定制模型的回答，但我们可以看到模型仍然偏离了预期，提供了通用的答案，而不是与我们的数据集一致的答案。这可能是因为 fine-tuning 需要更多的调整或更大的数据集。如果我们想更改源数据，就必须重新进行 fine-tuning 过程。

方法 2：RAG

为了使用 RAG 测试数据集，我们将使用 Playground 创建 RAG 应用并将数据集上传到 Kibana。

要通过 UI 上传 PDF 并配置语义文本字段，请按照此视频中的步骤操作：

上传 RAG dataset 到 Playground

要了解更多关于上传 PDF 并使用 Playground 与之互动的信息，你可以阅读这篇文章。

现在我们准备好使用 Playground 与数据进行互动了！通过 UI，我们可以更改 AI 指令并查看用于提供答案的文档来源。

当我们在 Playground 中提问相同的问题："What happens if a product is defective? " 时，我们得到了正确的答案："If a product is defective, we send you a free gift of one kilogram of pears along with the replacement." 此外，我们还得到了引用，以验证答案的来源，并可以查看模型遵循的指令：

如果我们想更改数据，只需更新索引，添加关于问答的信息。

总结

选择 fine-tuning 还是 RAG 取决于每个系统的需求。一个常见的模式是使用一些特定领域的 fine-tuned 模型，如 FinGPT 用于金融、LEGAL-BERT 用于法律，或 medAlpaca 用于医疗，以获取常用术语。然后，框定答案的上下文，并在其基础上构建一个 RAG 系统，结合公司特定的文档。

Fine-tuning 在你想管理模型行为时很有用，尤其是当通过 prompt engineering 无法实现时，或者需要太多的 tokens，最好将这些信息加入到训练中。或者，任务过于狭窄且结构化，模型蒸馏可能是最佳选择。

另一方面，RAG 擅长通过动态数据整合知识，确保实时的准确、最新的响应。这使得它在像 Pear Store 这样的场景中特别有用，因为政策和促销频繁变化。 RAG 还提供了以答案为基础的数据，并通过文档级安全性提供了按需分段信息的能力。

结合 fine-tuning 和 RAG 也可以是一个有效的策略，利用两者的优势，并根据特定项目需求量身定制解决方案。

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原文：RAG vs. Fine Tuning, a practical approach - Elasticsearch Labs